Review of Fundamental Developments in Analysis
Volumetric and Gravimetric Analytical Methods for Inorganic Compounds F. E. Beamish and John A. Page University o f Toronto, Toronto, Ontario, Canada
T
HE REVIEWS in the inorganic gravimetric field have indicated clearly the existence of a large surplus of precipitating reagents for such divalent elements as copper, zinc, mercury, palladium, and for thorium. For these metals, the authors have adhered to their previous policy of recording pertinent references only where some effort has been made to deal with the relative value of the proposed procedure. Undoubtedly, some of these omitted reagents will ultimately prove to offer distinct advantages over existing standard methods. Critical reviews of these numerous procedures would be a contribution. The current interest in radioactive elements has resulted in an increased number of gravimetric procedures for these heavy metals. Continued attention is also being given to analytical problems associated with surface adsorption such as contamination of precipitates, carrier coprecipitation, etc. In the field of volumetric analysis much of the work reviewed has been concerned with the use of general reagents. In some cases, selectivity has been achieved by careful control of the titration conditions, or by the use of masking reagents. In many cases the procedure is far from specific, and the methods w i l l have to be carefully esamined before application to particular problems.
GRAVIMETRIC ANALYSIS
General Gravimetric Reagents. Organic coprecipitants for quantitative separations are finding useful applications. hIaksimovic (47A) separated rare earth elements from uranium in a solution adjusted to pH 7 with ammonia and containing ammonium carbonate. Subsequent to the addition of 4,4'bis(4 - hydroxy 3 sulfopheny1azo)biphenyl and methyl violet a separation n as effected with very little contamination by uranium. While much of this type of work has not been applied to quantitative gravimetric determinations, this area of analytical work will
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find some profit in the recorded data and procedure. l-Nitro-2-hydrosy-3-naphthoic acid was used by Datta (19A)for the precipitation of uranium(V1) from solutions having a pH range of 3.4 to 4.5. The orange precipitate was dried at 120' C. Presumably the method is not applicable to very small amounts of uranium. The reagent has been used under the same conditions for the precipitation of thorium, zirconium, and palladium. For palladium the procedure has no useful advantages. Applications of 2-hydroxy-3-naphthoic acid and its derivatives as precipitants for cobalt, palladium, uranium, thorium, and titanium were recorded by Datta (18A). The nitro derivative was used successfully for titanium and the nitroso compound for the remaining four metals. The gravimetric applications of various new oximes were investigated by Dave and Talati ( H A ) who recorded three oximes which quantitatively precipitated palladium, copper, and nickel. The 8-mercaptoquinolates of more than two dozen metals were described by Kuznetsov and associates (57-4). The colored precipitates were soluble in various organic solvents and the data provided indicate a source of potentially useful solvent extractions and colorimetric methods of analysis. Precipitates of metals such as silver, copper, gold, osmium, palladium, platinum, and tungsten could he extracted from strongly acid solutions while lead, thallium, bismuth, selenium, tellurium, iridium, and nickel could be similarly isolated from weakly acid or neutral solutions. 5 - RIercapto - 3 - phenyl - 1,3,4,thiadiazole-2-thione (Bismuthiol 11)has been applied extensively to quantitative precipitations and. assisted by masking reagents, to a number of separations. Majumdar and coworkers (46A) precip itated bismuth in acid solution; the large number of intrrfering cations were reduced by a proper choice of acids or complexing reagents. All of the platinum metals could be precipitated in acid solutions, none in basic cyanide solutions, and in neutral cyanide solutions, platinum could be separated from
palladium. Methods for the precipitation and limited separation of thallium and silver were provided (43-4) and the reagent was also applied to copper and cadmium (46A) in the presence of masking reagents used to prevent interference from various associated metals. The composition of this reagent indicates useful applications to gravimetric determinations, the extent of which will require detailed researches. The applications to some dozen and a half cations of precipitants formed from sulfurous, selenious, and tellurous acids and various organic groups were discussed by Alimarin and Sotnikov ( S l l ) . Jlost of the cations produced sparingly soluble compounds. Organic derivatives of selenious acid precipitated quantitatively such quadrivalent cations as titanium, zirconium, hafnium, thorium, cerium, tin, and the cations niobium, tantalum, bismuth, and iron. The precipitants were salts of the acids and not chelate compounds. The optimum conditions for the precipitation of divalent manganese, cobalt, nickel, copper, zinc, and cadmium by anthranilic acid were discussed by Yatsimirskii and Kharitonov (94.4). A high basicity and excess of reagent were required in the presence of an acetate buffer. Soluble complexes were also formed in the presence of ammonia. Addition of salt to increase the ion concentration was desirable. Homogeneous Precipitation. Swift and associates (10A) have continued their efforts to present a rational basis for the analytical use of thioacetamide as a homogeneous precipitant for metal sulfi'des. The results confirmed the authors' previous conclusions that thioacetamide was not merely a homogeneous source of hydrogen sulfide. As in the case of lead (78A) a t least two reactions with cadmium were involved; in solutions of pH 2 and lower, precipitation of cadmium sulfide is dependent upon the supply of hydrogen sulfide resulting from hydrolysis of thioacetamide and is independent of the cadmium concentration; in solution with a higher pH the direct reaction becomes predominant and the rate of sulfide precipitation is first order with respect to both VOL. 32, NO. 5, APRIL 1960
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caclniium and thioacetamide concentrations and inversely half order with respect to hydrogen ion concentration. -In explanation of the latter dependence nil1 be of some interest. The data provided by the author were obtained a t 90" C. Under the conditions used the relative time required for complete precipitation of cadmium sulfide as compared to the classical gaseous method is very appreciably greater. There can be little doubt that the rela tively good control of the time of cadmium sulfide precipitation improved a i it will be by the use of loner teniperatures. will provide an excellent hackground for the understanding of coprecipitation phenomena. The authors also suggest that the explanation for a n increased rate of hydrolysis of thioacetamide basic solutions could be a direct reaction mechanism. It nil1 be hoped that all of these excellent researches n ill be continued. Thioacetamide has also been reconimended for the separation of zinc from nickel (8A). Compared to the gaseous precipitation. coprecipitation of nickel n-as inconsiderable and the physical characteristics of the zinc precipitate were greatly improved. Furthermore there was no overlapping or simultaneous precipitation of the nickel; subsequent removal of the latter, in the ahsence of iron, could be observed clearly. The separation is effected in an ammoniacal medium a t 70" C. and washing with ammoniacal sulfate. Too fen- data n-ere included but the method is worthj- of further investigation. A casual but interesting discussion of the reaction products of thioacetamide ancl niercury(I1j salts was reported by T'ozza (87A) who seemed unaware of the studies by Swift (78.4). Contrary t o the characteristics of hydrogen sulfideprecipitations, thioacetamide produced a variety of colored precipitates whose nature depended upon the concrntration of thioacetamide, the acidity of the precipitating medium, and the identity of the acid. The white compound, HgCl22CH3CsK1i2,isolated from the reaction mixture hydrolyzed in solution of pH 8 t o 0.1. yields black niercury(I1) sulfide. I n the presence of 1 to 3'11 thioacetamide various colored precipitates were formed. All of these had the coniposition niercury(I1) sulfide and in contrast to the black sulfide the colored sulfides could be converted to cinnahar by heating rvith caustic solution. The time of transition was related to the particle size. An exact and detailed examination of the homogeneous precipitation of mercury by thioacetamide would be informative and theoretically instructive. A modification of the phosphate precipitation of aluminum and its separation from the alkaline ea1th metals was developed by Krleia 250 R
ANALYTICAL CHEMISTRY
and associates (36A). The ammonia was introduced homogeneously by the hydrolysis a t 90' C. of carbamide and the optimum pH was 6.6 to 7.1. Coprecipitation. In previous rev i e w the senior author has given insufficient attention to publications which dealt with the character and mechanisms of nucleation. Obviously it is this early stage of precipit,ation n-hich t o a large degree determines the extent of contamination as surface area and rate of precipitation is thus predetermined. Klein and Gordon (3dd) provided a useful summary of t'he various theories associated with nuclcation. The short, discussion concerning the influence of impurities on the critical supersaturation ratio and the influence of precipitat,ion tcchnique on the early stages of precipitation are particularly significant. The present authors believe that homogeneous precipitation, providing as it does a n excellent control of t'he precipitant from almost zero to the critical value, will facilitat,e the determination of the nuclear size of the crystal particularly when the influx of the precipitant is low and the critical supersaturation ratio is high. The significant explanation for a relatively high dcgree of contamination in the early stages of a specific honiogeneous precipitation involves the heterogeneous charact'er of the initial precipitation resulting from a high supersaturation ratio. This suggestion may well provide improvements in homogeneous precipitations. Rudnev and 5Iazur (69-4)studied various aspects of contamination of the sulfides of mercury. copper. and cadmium by gallium, indium. and thallium. Their approach involved the use of hydrogen sulfide, radioact,ive forms of the three rare earth metals. surface active dyes, the electron microscope, and the electronograph. With a view to establishing the relationship betn-een coprecipitation a.nd the effective adsorption surface of the host precipitate the authors investigated the behavior of the sulfides upon continued digest.ion. It was found that mercuric sulfide disintegrated to form a very fine crystalline modification. Associated with this phenomenon, contamination by gallium and thallium-' decreased while with indium sulfide the degree of contamination remained unchanged. In the case of indium the dubious explanation offered mas the relative insolubility of indium sulfide. The reduced coprecipitation by gallium and thallium, despite the enlarged surface of the host. was essentially a case of reprecipitation assist.ed by the conversion of the mercuric sulfide to a crystalline form unsuitable for the dissolution of these two impurities. K i t h cadmium sulfide, continued digestion provided no increase in effec-
tive adsorbing surface. determined by the adsorption of dye, but as indicated by the electronograph. an internal conversion of the coagulated clumps to an accumulation of cadmium sulfide crystals n-hose size increased upon aging. Associated with these changes the contamination by gallium and indium increased with digestion, a process evplained by the increase of surface area due to crystallization within the aggregates. Strangely, thallium contamination decreased, the explanation for n hich n as not included. K i t h copper sulfide. aging resulted in crystallization together mith an increase in effective adsorbing surface. K i t h this increase in surface, contamination by indium increased rapidly on aging; with gallium there was an initial increase folloned by a slight decrease; nith thallium, aging produced no significant change in the degree of contamination. The authors' experimental data and their techniques are an important contribution and one may hope that this n-ork will be continued. However, there was little added to our knon-ledge of the mechanisms of coprecipitation. The authors discard the present explanations which involve the adsorption of HS-and S-* ions and also in the cases cited any extensive correlation between coprecipitation and surface area. Khile some support is provided for the contention that an enlarged surface area does not result necessarily in increased contamination, one is impressed n'ith the facility with which existing explanations are rejected and new ones postulated unsupported by experimental data. Indeed the authors fail even to clarify their expression, coprecipitation, although by inference, the processes of entrapping and solid dissolutions are included. Efremov and Andreeva (MA) also dealt with the coprecipitation of thallium with cadmium sulfide over various ranges of acidity. The mechanism TVBS a surface adsorption and the amount of coprecipitated thallium increased with increase in basicity and with increase in the mass of the cadmium sulfide. ;iceording to Korenman and Shatalina (%A). the coprecipitation of cesium with the dipicrylamines of potassium and thallium + I was isomorphic in character and was not influenced by the order of addition of solutions or the temperature of precipitation except in so far as the solubility of the precipitate n as affected. Thermogravimetry. Disagreements concerning the thermal behavior of precipitates continue t o appear, in many instances, arising out of variations in technique. Wendlandt and Brabson (90A) re-examined the thermal behavior of molybdophosphate of 8quinolinol. A prior publication by D:iral (94.4) indicated that. in addition
to the oxide level at 800" to 852" C., a horizontal appeared between 176" to 225' C. which corresponded to either one of tlvo hydrated compounds of the same elementary composition; there was no evidence of an anhydrous form. Wendlandt and Brabson found no evidence of Duval's alternative compounds. The air-dried quinolinol compleu, 3C~HiOSH3(P~IO1?0~~.2H formed Z0 the anhydrous salt between 85" and 235" C. At 335' to 375' C. a horizontal appeared corresponding to a loss of two formula n-eights of 8-quinolinol. The thermogram obtained from the precipitate dried a t 140' C. duplicated the air-dried sample very nicely and neither resembled those published by Duval. However. the authors used the procedure recorded by Brabson and Edwards (11;1) which, unlike the older method used by Duval, avoided the use of ammonium nitrate as a wash liquid, and i t was t o this variation in procedure that Wendlandt ascribes the complete dissimilarity of the thermograms. Presumably, Wendlandt made no effort to wrify this guess experimentally. In the present authors' opinion, the answer to the effects of such variations often constitute a greater contribution to analytical chemistry than the mere recording of a variety of thermograms. Indeed. one may doubt the wisdom of publishing thermogravimetric researches which ignore the effects of variations of procedure on the compositions and thermal behavior of the resulting precipitates. In the case of this quinolinol phosphomolybdate further complicating data were provided by Gottschalk (2929A) who, like Duval, used the ammonium nitrate wash liquid, but unlike both Duval and Wendlandt obtained Wendlandt's anhydrous compound only a t 160' C. Unlike Wendlandt but like Duval and earlier investigators, Gottschalk accepted the composition of the precipitate as 3HOX. H?[P(hiozO;)a]. 2Hz0but preferred to write the formula [HOX(H30) 1 3 . HzO [P(Mo&)4] to indicate that one formula weight of water was relatively easily removed, that three formula weights of water were removed with difficulty (probably because they were coordinated with the 8-quinolinol) , and that the coordination number of the phosphorus was four rather than six. -4side from these, perhaps understandable differences, there exists the wide variation in the temperature range for the oxide level which begins in one case a t 470" C. (884) and in another a t 800' C. (24A). This is indeed a muddle of some dimensions; surely this single instance will justify the hope for thorough examination of the thermal behavior of a discriminating choice of precipitates. With a view to clarifying conflicting
thermal data for rare earth metal oxalates, Caro and Loriers (15A) took special precautions to approach equilibrium conditions during the decomposition processes. To the degree that this is one done may expect reproducible mass-temperature curves and more precisely delineated zones of stability. The authors' results emphasize the importance of heating rates. The basic carbonate, M203. CO?, did not occur with rare earth elements having oxidation states above three. With the remaining metals it was found that the stability of this single well-characterized basic carbonate varied inversely with the atomic number of the metal, the relatively acidic scandium producing no basic carbonate. I t is to be hoped that the large number of precipitants for thorium will be examined with a view to establishing the most suitable areas of application and their relative efficiency. Wendlandt (89A) has recorded thermal decomposition curves for some 10 reagents and found considerable variations in their heat stability. The oxide levels were reached in all cases far below the 1000" C. ignition temperatures advocated in some publications. The authors' data suggest also the possibility that certain of the procedures previously recommending oxidation will permit a direct weighing of the precipitate. -4 rapid method for determining calcium and magnesium in dolomitic rocks was recorded by Dupuis and Dupuis (%?A). The precipitated carbonates mere first heated to 500' C. to produce magnesium oxide and calcium carbonate and then to 900°C. to obtain calcium and magnesium oxide. Iron and aluminum interfered. Rapid methods such as this can be useful when a p plied to rocks containing appreciable proportions of both calcium and magnesium carbonates. A new design of a thermographic balance was described by Pale7 and associates (56A). With a capacity of 30 to 50 mg., it could be used for continuous recording of temperature-weight or time-weight if the changes were no greater than 20 mg. Preparation for Weighing. For the analyst who wishes t o reach beyond the accuracy limited by variations in air density, Lupke (424) has suggested a simple formula which permits an estimate of the apparent weight change with air density fluctuations. A useful chart was provided from which one mayreadily obtain the quantitative relationships between air density and temperature, barometric pressure and reIative humidity. Bud&insky (1SA) considered the effect of the volume of the precipitate on the accuracy of determinations and recorded equations to correct for errors arising therefrom. There has been a continued interest
in gravimetric methods which are designed to avoid filtering and ignition processes. Pel'sh (578) described a simplified technique which * involves washing, drying, and weighing in centrifuge tubes. Very acceptable accuracy was reported for some of the common cations and anions whose weights nere within the semimicro scale. Light Alloy Elements. ~IAGSESIUJI. An interesting application of (ethylenedinitrilo) tetraacetic acid (EDTA) for gravimetric purposes was described by Brickcr and Parker (12.1). By a method fraught with difficulties, this reagent precipitated magnesium as ?*IgCloH140aS2 6H20. The optiniuni pH range was narrow, precipitation \vas objectionably slow, the relationship of the reactants was intricate, and for the room tcmperatuie drying an empirical factor was recommended. Strangely the latter yielded slightly better results than those obtained by drying a t more elevated temperatures, which condition allowed the quantitative formation of the anhydrous salt. Unfortunately the precipitate was not subjected to thermogravimetric techniques. The method will find only restricted use for the determination of magnesium but it is of theoretical interest and with some improvement can be useful for the isolation of EDTA. Vishveshwaraiah and Pate1 ( M A ) described a method for the determination of lithium as phosphate which avoided interferences from five times the weight of sodium or potassium. Procedures for the determination varied somewhat with the weight of lithium to be determined. The phosphate reagent contained 2diethylaminoethanol adjusted to pH 9.0 to 9..5. The precipitating medium contained ethyl alcohol and the precipitate was washed with a solution of lithium phosphate. The results reported indicated good accuracy. Rare Earth Elements. The magnitude of the losses associated with the [kit of oxalic acid for the isolation of rare earth elements and thorium from monazite sands was investigated by Clinch and Simpson (17.4). With an insufficient excess of oxalic acid the thorium losses increased with increase of nitric acid content but the reverse effect was encountered when large excesses of oxalic were present. The general behavior of the lanthanons was determined by the use of cerium and here large excesses of oxalic and increasing proportions of nitric acids materially increased the loss. In spite of the fact that ammonium salts encouraged losses of the lanthanum, ammonium oxalate was the preferred reagent, and for the lanthanons, a large excess' was required with minimum acidity before precipitation. As would be expected, calcium was coprecipitated. "01.32, NO. 5 , APRIL 1360
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The authors opened the monazite sand with perchloric acid, and subsequent t o the isolation of thorium and lanthanum by double precipitation, the former was removed by benzoic acid precipitation and the latter isolated from calcium, etc., in an ammoniacal solution. Of considerable interest is the comparison of the efficiencies of the proposed method with four older and widely used procedures. There is the conclusion that the proposed method has considerably smaller thorium losses than any of the previous methods investigated. The included data associated n ith the latter indicate discouragingly high solubility losses and coprecipitation errors. Group separations of the rare earth elcnients were studied by Vagina (84.4). Of the four reagents examined the precipitation by ammonium oxalate was considered to be the most effective method. In the presence of EDTA yttrium, gadolinium, terbium, and dysprosium were precipitated and thus separated from holmium, erbium, thulium, ytterbium, and lutetium. The effect of varying acidity was also discussed. An improved method for the isolation of scandium from rare earth elements and zirconium has been reported (61.4). In the prekence of the former, together with ammonium fluoride, scandium is removed by ammonium fluoride to form the soluble ammonium hexafluoscandiate, Zirconium is separated as the phosphate. On the other hand, Takashima (80A) used sodium fluoride and hexamine cobalt chloride a t pH 3 to 4 to precipitate [Co(NH&][ScF,]. The yellow precipitate was dricd a t 1JO' C. The method can be used for very small amounts of scandium, Rao and coworkers (68.4) used potassium chromate to precipitate lanthanum in the presence of rare earth elements and in the absence of cerium. The procedure applied to monazite involved a prcliminary treatment of the solution with magnesia to remove thorium and cerium, isolation of the rare earths as oxalates, dissolution, precipitation and reprecipitation of lanthanum by chromat? a t pH 5.7. The lanthanum is finally converted to oxalate and then to oxide While the procedure is laborious, the results indicated excellent recovery for optimum ratios of lanthanum and asqociated oxides. Various procedures for the precipitation of cerium periodate have been recorded, between some of which there are variances of data. Puzdrenkova et al (66A) used the periodate a t pH 2 to 7 to precipitate the trihydrate which yielded the anhydrous salt above 100' C. With a fivefold excess of precipitant the trivalent cerium was oxidized to the quadrivalent state. Previous publications recommended the 252 R *
ANALYTICAL CHEMISTRY
periodate method for the separation in 2N acid of quadrivalent cerium from thorium, rare earth elements, and trivalent cerium. The composition of the precipitate dried at 100' to 110' C. was recorded as the monohydrate. Radioactive Elements. THORIUM, URANIGM, PLUTONIUM. While a rather large number of new precipitants for thoIium have been recorded, few iniprovements over the numerous older methods have appeared. Yen et al. (95.4) precipitated thorium selenite homogeneously a t pH 1.8 from solutions of thorium nitrate, selenious acid, and acetamide. Between pH 2.0 and 2.3 there was no interfcrence in a single precipitation from rare earth elements up to 10 times the proportion of thorium oxide. Optimum conditions for the precipitation of uranium(1V) orthophosphate were discussed by Strandell (77.4). In hydrochloric acid solutions of uranium, aluminum, and orthophosphoric acid, precipitation is prevented by soluble complexes of these constituents, particularly with a high aluminum content. In the corresponding sulfate solutions, the optimum p H range of 1 is critical. Both higher and lower acidities result in various soluble complexes. Cacodylic acid was used by Pietsch (68A) to precipitate uranium (VI) as UOz(ASOMez)za t pH 4 to 7, which could be converted to U308 a t 950" to 1000' C. or weighed directly subsequent to filtering with a sintered glass crucible and drying a t 200' C. In a second paper, the author (68A) provided further data and an improved technique. The above procedure is worthy of further investigation. An interesting method for the precipitation of uranium was recorded by N&scutiu (66A). A precipitate with a formula weight of 950.40 was produced by the addition to a solution of uranyl nitrate or acetate of C03("4)2 in slight excess, then a concentrated solution of [CO(NH3)S](N03)3.The precipitate in a Gooch crucible was washed with an ethyl alcohol solution of the precipitant, then with absolute ethyl alcohol andwith ether, dried in vacuo, and weighed. Cupferron has been used by various authors to precipitate uranium. XIost of these procedures involve prior precipitating separations. Bieber and VeEefa (7.4) used ammonium(ethy1enediamine) tetraacetate or tartaric acid to mask a variety of interferences with the exception of titanium, beryllium, zirconium, fluorine, and carbonate. A procedure for ores and concentrates was included with final ignition a t 800' to 1000' C. Phenylglycine-o-carboxylic acid was recommended by Datta (d0A) as a precipitant for uranium subsequent to reduction by a Jones reductor. Precipitation was carried out a t 5' C. followed by continued cooling, mashing with water
and ethyl alcohol, and ignition to Directions were included for the separation of thorium and zirconium. Potassium iodate has again been recommended as a precipitant for uranium. While previous methods produced the weighing form UOZ(IO&, Przheval'skiI et al. (60A) stated that, with specific ratios of sulfuric acid to potassium iodate, U(103)r was produced as the weighing form which could be treated volumetrically. 1,3-d-m-Tolylvioluric acid and its p-tolyl analog were used by Bhargava and associates ( 6 A ) to precipitate uranyl ions (UO+*) present as the acetate. Because no analytical data were included, further lyork is required to indicate its value relative to the few uranium gravimetric reagents. Factors affecting the carrying efficiency of lanthanum fluoride as a collector of plutonium were investigated by Monk (60A). I t was shown that the principal error in the plutonium recovery was not due to incomplete precipitation of lanthanum fluoride. The author recorded a procedure which permitted an accuracy of better than 99.9%. Alkali and Alkaline Earth Elements. SODIUM, POTASSIUM, BARIUM. 1Amino-8-naphthalenesulfonic acid has been used to precipitate sodium with results comparable to those obtained with magnesium uranyl acetate (6.4). A variety of new gravimetric reagents for potassium have been recorded by Toei ( 8 1 4 82A). One could hope that a criterion for the publication of new reagents would include data dealing with relative efficiency of procedures. Tetranitroacridone and tetranitrophenothiazine oxides are merely recorded aa new precipitants with interference from sodium and magnesium. Comparative characteristics of three methods for determining potassium in silicates were described by hlurina (6SA) and associates. The chloroplatinate, perchlorate, and dipicrylamine methods of precipitation and separation from sodium were examined by using potassium-42 and sodium-24. Comparable precision was obtained with all three reagents but the dipicrylamine method required less time and it was more generally useful. The useful applications of EDTA to the determinations of alkaline earth elements have been extended by Busev and Kiseleva ( I q A ) to provide a method for the reprecipitation of barium sulfate. The latter was dissolved in an ammoniacal solution of the disodium salt and the solution heated in the presence of hydrochloric and sulfuric acids to produce a precipitate with good physical characteristics. To avoid low values for barium resulting from the use of dilute sulfuric acid solutions, approximately 0.1N, Gupta and Bhattacharya (3'1.4) used aqueous alcohoi or acetone solutions to reduce the solubility produ30,.
uct from about 10 X lo-" to 2 X 10-11. Steel-Forming Elements. TITANIUM, ZIRCONIUM, MOLYBDENUM, TAXTALUM, XIOBIUM. Procedures for the separation of titanium from niobium and tantalum and niobium from tantalum by acridine were recorded by Malyarov and Gibalo (MA, 48.4). Titanium in an oxalic acid medium was precipitated by acridine t o form H2[Ti0(CzO4)2]2C13H~N. Xiobium and tantalum were subsequently hydrolyzed and weighed as the mixed oxides. The latter elements could be fused with pyrosulfate and, in the presence of tartaric acid, tantalum waq selectively precipitated by acridine. The data indicated poor accuracy. For the precipitation of zirconium, Ryazanov and Milin (70.4) preferred monoethanolamine to cupferron, thiosulfate, phenylarsone, etc. The hydrated oxide was precipitated from a nitric acid solution and burned at 800" to 900' C. Unfortunately the accuracy of the method was affected by the amount of the reagent. Researches continue in the difficult field of niobium-tantalum separation. In general, much of this work is concerned with improved applications of known methods. The cupferron separation was discussed by hlajumdar and Chowdhury (44.4) who precipitated niobium in the presence of tantalum a t pH 4.5 to 5.5. Ratios of the metals at 30 to 1 and 1 to 30 were separated with tin(I1) and (IV) as collecting agents. Rao, Sarma, and Rao (67.4) extended the morin reaction by arranging the dissolution of the nicbium complexin acetone-sulfuric acid solution. The tantalum complex was washed with aqucous ethyl alcohol and ignited to the ouide. In the presence of oxalic acid t h e two metals could be precipitated by morin in the presence of zirconium. A method for the determination of tantalum and its separation from some of the associated metals of columns IV, V. and VI was described by Mosmier and Schwarberg (62.4). The precipitant, N-benzoyl-N-phenylhydroxylamine. was used in a hydrofluoric acidsulfuric acid medium a t pH 1.0. Although hydrofluoric acid reduced the tendency for simultaneous precipitation of niobium, prolongation of the period of standing encouraged this contamination. In addition to this difficulty appreciable losws were introduced a t temperatures greater than 27" C., and a t acidities greater, than pH 1.2. It was necessary also to wash with a saturated aqueous solution of the reagent. The prior separation of molybdenum and tungsten was accomplished by collective precipitation with cupferron of tantalum, niobium, titanium, and zirconium and by numerous washings with cupferron wash solution followed by
ammonium hydroxide solutions. The values for this separation recorded by the authors indicate acceptable accuracy. For the determination of tantalum in the presence of niobium, titanium, and zirconium, from one to three precipitations were required. While the positive errors revealed by the data provided were not insignificant, the method, when carried out carefully, appears promising. For the precipitation of niobium and its separation from tantalum Belekar and Athanvale (4.4) used 8-quinolinol in a tartrate medium a t pH 6. The precipitate was ignited in the presence of oxalic acid to avoid loss by volatilization. Further purification was effected by a series of selective extractions. Tin and antimony could be removed as sulfides from the 8-quinolinol filtrate. Tantalum could be precipitated from the latter filtrate in the absence of tin and antimony. Titanium waa distributed between the niobium and tantalum precipitates. The data indicate acceptable accuracy over the range of 2 to 100 mg. of the oxides. Further work on the precipitation of molybdenum as brick-red [Cr(NHJt.Cl] [?tIoS4]has been recorded by Spacu and Gheorghiu ( 7 3 A ) . Masking reagents to prevent interference from various associated cations were discussed and a method for the preparation of the reagent was included. A wide variety of methods for the precipitation of molybdenum(V1) sulfide have been recorded during the past decade. Undoubtedly, one of the most useful is the homogeneous precipitation by thioacetamide. McNerney and Wagner ( @ A ) provide results obtained on titanium alloys which indicate exceptionally high accuracy. In general, the procedure involves the usual reactions. Certain misconceptions concerning the precipitation of molybdenum by 8quinolinol were discussed by Rao (66.4). At the recommended pH's of about 3 to 7 , there existed an equilibrium between the dipositive molybdenyl cation and the hlo7OZrl4anion-the latter anion predominating toward the acid range. As the precipitate with 8-quinolinol was formed by the molybdeny1 cation, it was clear that within the more acid range molybdenyl would not interfere when 8-quinolinol was used to precipitate uranium a t pH 8.1 to 8.9, over which range the anion was not stable; thus the reagent EDTA, recommended as a masking reagent in the basic medium, was ineffective. TUNGSTEN AND COBALT.Zato and coworkers (41.4) have continued to record new reagents for the precipitation of tungsten. Analogs of 4,4'-diaminotriphenylmethane have been recorded and, commendably, an effort .IS being made to apply the reagents to ores and to estimate their value relative t o estab-
lished reagents. The relative efficiency of various precipitating reagents for tungsten was also investigated by Claeys (16A). Precipitation' of the sexivalent oxide by mineral acids was not recommended. Tannin was also rejected. The most efficient reagents, producing a recovery of better than 99.9%, were cinchonine and p-naphthoquinoline. Of lesser value were benaidine, +toluidine, phenazone, and Rhodamine B. Liang (38A) and associates also continue to record researches on the determination of tungsten. Contrary to accepted opinions the effect of carbon dioxide in air on the determination of barium tungstate is considered insignificant. The suitable ignition range was 500' to 900' C. and the precipitant barium acetate was considered superior to barium chloride. For the determination of cobalt in the presence of nickel, Pirtea and Antonescu (69A) added sodium nitrite in the presence of acetic acid to produce N a r [Co(NO&,]; an excess of [Co(NH~)slCls then precipitated [Co(NH&] [Co(NO& 1 which was washed successively with the hexamine cobalt chloride, ethyl alcohol, and ether, and dried in vacuo. Potassium and ammonium ions interfered. Nonferrous Metals. THALLIUM AND BISMUTH. An examination of the dichromate method for the precipitation of univalent thallium was made by Bashilova ( S A ) . High results were obtained by the precipitants, potassium and ammonium dichromates. The sodium salt or chromium(V1) oxide were the preferred reagents and were used in the presence of sulfuric or nitric acids. There Eas no interference from larger amounts of the sulfaks of zinc, cadmium, aluminum, iron(II), copper (11), nickel, cobalt, indium, and gallium nor from smaller amounts of the nitrates of silver, bismuth, mercury(II), lead, and barium. The thallium dichromate precipitate was found to be an incongruently melting compound whose composition was not affected by washing with ether or ethyl alcohol. Washing with water and ether produced tl slight decomposition. Some of these data are a t considerable variance with earlier literature and further studies would be useful In view of this wide disagreement, it is unfortunate that the original article and its translation were not available. The value of gallic acid as a precipitant for bismuth remains disputed. Dick and Mihai (22A) used the reagent to precipitate CsHpOsBi from a nitric acid solution containing lead. The yellow precipitate was washed with ethyl alcohol and ether, dried and weighed. Confirmation of this work would seem desirable. Noble Elements. SILVERAND GOLD. Interesting data on the distribution of silver losses during fire assay processes VOL 32, NO. 5, APRIL 1960
253 R
effects on precipitations of platinum were recorded by Nakamura and metals of various derivatives of thiourea, Fukami (544) who used silver-110 as a urea, and guanidine (MA). The intracer. Most of the loss occurred in the troduction of phenyl heterocyclic groups cupel; the percentage loss increased, with decreasing amounts of silver. into thiourea or guanidine encouraged the quantitative applications to the During the past decade about one dozen platinum metals; on the other hand, new reagents have been proposed for base metal precipitations were ensilver. It will be hoped that some effort couraged by introducing certain acid will be forthcoming to evaluate these relatively. Spacu and coworkers ( 7 2 ~ 4 , groups into phenyl rings of diphenylthiourea. For the precipitation of 7 4 4 ) have extended their applications iridium the thiourea series was preferred. of complex organic reagents to produce The introduction of a third substituent two heavy silver precipitates. Potasinto guanidine increased the solubility of sium iodide and [Cr4(OH)6en~I6]proits platinum metal complexes. A deduced the crystalline precipitate [Ag12]r tailed procedure for the precipitation of [Cr4(0H)6ens]Id ( 7 2 A ) . In the second platinum by phenothiazine to produce a method the silver salt was treated with pure complex was also described. The picric acid and thiourea to produce method was applied satisfactorily to [A~(CSNZH~)ZI(C~HZH~O~). synthetic mixtures and to alloys and was To precipitate gold from cyanide solutions Karasev and associates ( S S A ) considered superior to precipitation by used mercaptobenzothiazole or sodium formic acid. The precipitant thioanalide, previously used for the gravisulfide. For high gold dilutions or very metric determination of ruthenium, was impure cyanide solutions the method found suitable for the quantitative preyielded more accurate and precise results cipitation of platinum, palladium, rhothan the usual zinc precipitation. The dium, and iridium (62A). In the case procedure involved precipitation in a of iridium, prior reduction by ethyl alcosulfuric acid solution in the presence of hol was required. Confirmation of silver nitrate. The mixed precipitate these data would be a contribution. was scorified and cupelled to form a bead Only a few gravimetric reagents have which was parted in the usual manner. PLaTINuM METALS. 2.1 study of been reported for rhodium Watanabe organic compounds containing the (88A) used 1-nitroso-2-naphthol in acetic acid solution at pH 4.85 to 6 to groups C1, NH2, OH, SH, NO,, and form a precipitate which was ignited to OCHB, examined for their ability to rhodium(II1) oxide. Acetic acid soluprecipitate platinum metals, indicated tions of 1,2,3-benzotriazole were used that their usefulness increased with the ( M A ) in nitrate solutions of rhodium molecular polarity. Phenothiazine proneutralized with sodium acetate to produced the most stable complexes and duce Rh(C6H4N1\1'z)3.3H20.The prethese, among others, were selective for cipitate was washed with acetic acid and the platinum metals group (64A). dried a t 110' C. for 2 hours. Similarly, An interesting method for the detersolutions of rhodium iodide, bromide, mination of iridium and rhodium by and sulfate produced about 100% yield thiourea was recorded by Pshenitsyn of insoluble precipitates. Pshenitsyn and Prokof'eva (6SA). Sufficient thiourea was added to produce an excess and Fedorenko (61A) used p-aminophenyldithiocarbamate to precipitate a over the amount required for maximum yellow-orange trivalent rhodium precoordination. Subsequent to a heating cipitate and brownish orange trivalent period concentrated sulfuric acid was iridium compound. The method was added and heating continued t o a colorless supernatant solution. The brown not satisfactory when applied to mixtures of the two metals and extraction sulfide of iridium appeared a t 180' to of either compound by solvent extrac190' C.; the black sulfide of rhodium tion was ineffective. At a pH of 2 to 7 appeared a t 150' to 170' C.; platinum for rhodium and 3 to 5 for iridium the and palladium sulfides precipitated a t 190' to 200' C.; ruthenium sulfide precipitates were colloidal. Coagulation was effected by methyl violet which precipitated a t 120' to 140' C. The ideally should equal the weight of metal sulfides were washed, dried, and ignited precipitated. The chloride salts of followed by reduction with hydrogen. rhodium or iridium were treated with The tables of results indicate an accuracy appreciably less than can sodium chloride to remove completely the hydrochloric acid. The precipitates be obtained by some of the existing were ignited and reduced by hydrogen. methods. Presumably the thiourea The accuracy and precision of the method for rhodium and iridium avoids method are not of a good order, but as some interference from nickel and iron. precipitants for rhodium and iridium are Because copper, lead, and tin coprenot numerous, the procedure should recipitated one cannot emphasize the freeceive further examination. dom from interference. The authors A large number of precipitants for recommend the method for group isolapalladium have been recorded, for many tion of platinum metals and this claim of which there have been no indications will justify further investigations. of relative merit. These have not been An informative paper deals with the 254 R
ANALYTICAL CHEMISTRY
jncluded in the present review. The use of triazoles 1,2,3-benzotriazole and 5bromo-1,2,3-benzotriazole for the precipitation of palladium was discussed by Lomakina and Tarasevich (39.4). The former reagent had previously been described by Wilson and Wilson (QZA), who recorded a slightly different empirical formula for the precipitate and indicated some difference of opinion in the extent of interference from associated metals. Of the latter the effects of gold and nickel are of some importance. The applications of xanthates, dithiophosphates, and alkyl and aryl mercaptides as precipitants for palladium were discussed by Karasev and Kakovskil (S2A). With sodium ethylxanthate, palladium and gold were precipitated completely in the presence of platinum, rhodium, iridium, iron, and other heavy metals. The precipitant for osmium developed by Wilson and Baye (91A) provides the only existing method for direct gravimetric determination. 1,2,3-Benaotriazole was used in an acetic acid-acetate buffer to provide a yellow compound which is stable up to 200' C. There remains the problem of adapting the method to the solutions which are used for the collection of the octavalent oxide of osmium. Nonmetallic Elements. BOROSASD PHOSPHORUS.Few gravimetric reagents for boron have been recorded. A potentially useful procedure involving the precipitation of the tetrafluoborate ion bv 1,4-diphenyl-3,5endanilohydrotriazol (Nitron), was recorded by Lucchesi and De Ford (40A). Over the range 125 to 250 mg. of boric acid the results averaged 0.7 =t 1.0% high. Smaller samples mere not used. The slow reaction between the added hydrofluoric acid and boric acid assimilated a homogeneous precipitation by Nitron. Ten to 20 hours' standing followed by 2 hours in an ice bath was recommended. The precipitate was washed with a saturated solution of the precipitate and dried a t 105' to 110' C. There was some corrosion of the crucible but the loss was a small part of the average error. Undoubtedly, the precision, accuracy, and specificity of this method could be appreciably improved by extended investigations. The compositions of molybdophosphates and suitable conditions for precipitation were discussed in good detail by Stockdale (76A). The yellow precipitate obtained from the orthophosphate in the presence of large excesses of nitric acid and ammonium nitrate was found t o be (NH&H [P(M0301o)11.H20 rather than the triammonium salt (NH4)3[P(M03010)4]HN03.2H20. The latter, freed from nitric acid and water, was obtained by washing the yellow precipitate with ammonium nitrate. The effects of stirring, time and tem-
perature of digestion, identity of rvashing liquid, purity of reagents, and excess of molybdic oxide and nitric acid were discussed. Of these factors the last was considered to be of primary importance. With too little molybdic oxide and too much nitric acid some phosphate remains in solution, and with the concentration reversed the precipitate was too heavy. Procedures for the gravimetric determination of total phosphate in basic slag and steel were included and the author discussed the relative efficiencies of various methods of effecting dissolution, the influence of sulfate and iron, and the purification of the precipitate. As simple dissolution and reprecipitation of the phosphomolybdate are inexplicably unsatisfactory, the method of purification consists in precipitating the phosphate with a large excess of molybdic oxide, removal of the latter as a sulfide, and subsequent reprecipitation of the niolybdophosphate. An interesting method of reprecipitation subsequent to the isolation of ammonium phosphomolybdate was described by Gheorghiu and Radulescu ( 2 7 8 ) . These authors dissolved the yellow precipitate with ammonia, then added hydrogen sulfide to produce a red qolution from which [MoS~] [Cr(NH3)&1] 11as precipitated by the addition of [Cr(NH3)5C1]Clz. The precipitate was washed with the chloropentamino chromium chloride reagent, ethyl alcohol and ether, and dried in vacuo. Lead orthophosphate (85A) was used as a weighing form, subsequent to calcination a t 600" to 700" C. for the determination of phosphates in buffered solutions of pH 2 to 3. The precipitant was lead acetate and the wash liquid was acetic acid solution. The accuracy was comparable to the best classical methods. For the determination of phosphates there is a steadily increasing accumulation of procedures which involve the use of hexamine cobalt(II1) and trisethylenediamine cobalt(II1) salts. Some benefit would accrue from a more efficient liaison in this analytical area. There is a lack of unanimity concerning the compositions of precipitates and presumably a lack of knowledge of contemporary publications. Recently, Spacu and Vasilescu (75A) Precipitated :>!-rophosphate by hexamine cobalt(II1) nitrate in ammoniacal medium to protluce the weighing form [Co(NH&]SaPzO,. Takashima (79A) used the chloride form of the precipitant for the ortho-, tris-, and pyrophosphates and for the last one accepted the weighing form as CO(NH~)~HP,O?. With trisPtliylenediamine cobalt bromide and pyrophosphate a t pH 6.5 to 6.7, Akiyama and coworkers ( I A ) used the weighing from Co(en)SH. PaO?.2Hz0. In all cases the accuracy of recovery seeins to be of a low order. The influ-
ence of polyphosphate on the precipitation of ammonium magnesium phosphate was discussed by Grunze (SOA). The ratio of magnesium bound to the polyphosphate was found to be a function of their relative concentrations. In addition t o this interference excess of magnesium added to solutions of the mono- and polyphosphates produced a precipitate whose phosphate content was stoichiometrically high. ANTIMONY, SELENIUM,FLUORINE. The extensive applications of thiosalts used by Salaria and coworkers (YlA) for the quantitative determinations of cations now include the precipitation of quinquevalent antimony sulfide. The thiosalt is first formed with alkali sulfide and antimony(V) sulfide subsequently precipitated b y hydrochloric acid. It is to be hoped that these many procedures will receive the critical attention of analytical chemists. T o separate and determine selenium (IV) in the presence of selenium(VI), Bode and Stemmer ( 9 A ) used sulfur dioxide under pressure in a 0.5N hydrochloric acid solution. Selenium(V1) was precipitated similarly from the filtrate adjusted to 4 to 5N with hydrochloric acid. The data recorded indicated a satisfactory degree of accuracy for samples with widely differing proportions of selenium(1V) and (VI). As would be expected, there is a considerable number of interfering metals such as most of the platinum metals, silver, tellurium, univalent mercury, lead, and copper. At acidities of higher than IN hydrochloric acid there may be interference from alkali chloride and nitrate. An experimental comparison of methods for the determination of fluorine was reported by Funasaka, Kawane. and Kojina (26.4). Precipitation m PbFCl was considered superior to calcium fluoride procedures from the view points of accuracy, precision, ease of operation, and length of time required. VOLUMETRIC ANALYSIS
As in the case of the gravimetric analysis review, it was necessary to impose arbitrary restrictions on the material to be included. Titrations involving electrolytic generation of the reagent, and titrations employing potentiometric and amperometric methods for establishing the end point are not included. The review, it is hoped, is confined t o those methods that are new, unique, or constitute improvements in the known procedures. Organic precipitating reagents continue to be of interest, both as direct titrants and for indirect determinations in which the precipitate is filtered off, dissolved, and the organic reagent equivalent to the metal then titrated. I n some cases the reagents are far from specific, and prior separations may be
necessary before a method can be used on a particular sample. Bobtelsky and coworkers have continued their studies of the hetwometric titration technique and have reported methods for bismuth (ZlB, 28B), cadmium (29B), mercury (MB),silver (WSB), and gold, palladium, and platinum (%B, %@,26B, 27B). Bagbanly and coworkers have used Reinecke's salt [K,Cr(CNS)a] for the determination of bismuth (YB),copper (6B,IOB), silver (8B),and thallium (9B). The precipitates after decomposition are titrated with potassium iodate. In the case of the copper(1) and thallium(1) precip itates, the metal is oxidized along with the thiocyanate. The procedure% are fairly specific and gave accurate results. Maj umdar and coworkers have used Bismuthiol I1 (5-mercapto-3-phenyl-2thiol-l,3,4-thiadiazol-2-one) for the indirect determination of cadmium (8QB), lead and silver (88B), and bismuth and palladium (85B). In the cme of bismuth, cadmium, and lead the precipitates were dissolved in excess EDTA followed by a back-titration of the excess with magnesium, but for palladium and silver the precipitate wm dissolved in excess potassium cyanide followed by a silver nitrate back-titration. Results were good, but care must be taken to avoid the coprecipitation of other elements. Other methods using organic reagents are discussed under the individual elements. Ion exchange resins are finding use not only in the separations prior to the determinations, but in the actual determinations. Acid-base indicators adsorbed on resins give a sharp color transition on an indicator phase separate from the solution (92B). Magnesium has been determined by precipitation as MgNH4PO4.6H20, dissolution and passage of the solution through a cation exchanger in the hydrogen form, and then titration of the liberated acid (61B). Boron has been concentrated on Dowex 1 saturated with gluconic acid and then eluted with sodium chloride for the mannitol titration (S8B). Calcium and magnesium have been selectively eluted from a cation exchanger with buffered stapdard EDTA solutions, and the determination was made by titrating the uncomplexed EDTA in the filtrate (14QB). A complexometric determination of the sum of sodium and potassium involves passing a neutral solution through a cation exchanger in the magnesium form and titrating the magnesium in the eluent with EDTA (59B). A number of investigators have used radiometric methods to indicate the end point in titrations. For example, Alimarin and Gibalo (BB)use diammonium hydrogen phosphate tagged with phosphoru-32 to titrate beryllium. The VOL. 32, NO. 5, APRIL 1960
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equivalence point was found graphically by centrifuging off the precipitated beryllium phosphate and measuring the activity of the solution a t intervals throughout the titration. The special value of these methods will appear to lie in the titration of micro amounts of constituents, as they are too cumbersome to replace the standard methods of end point detection. Photometric methods have been used to detect the end point in a number of titrations. The method has been used frequently with EDTA. Bricker and Schonberg (SSB)have recorded the first photometric titration. An iron(II1)oxalic acid solution on irradiation with a mercury arc produces iron(I1). The reductant thus generated reacts stepn-ise with chromium(V1) or vanadium (V) in the solution, the end points being detected photometrically. The quantum yield of iron(I1) is constant throughout the irradiation, and the exposure time taken to reach the end point is directly proportional to the amount of the oxidant. EDTA. Flaschka, Barnard, and Broad have reviewed the applications in one of their series of articles ( I @ ) and no attempt will be made here t o enlarge on their survey of this popular and valuable reagent. The theory of indicators for complexometric titrations has been discussed in detail by Flaschka (5dB) and Reilley and Schmidt (115B), and the sharpness of the end points has been characterized. Of interest is the use of oxidation-reduction indicator to mark the end point in EDTA titrations. Variamine Blue (48B) and benzidine (119B) in the presence of ferro-ferricyanide and vanadium(V) in the presence of an oxidation-reduction indicator (IdOB) have all been used. An intrresting method of indirect analysis uses a liquid amalgam to give selective reduction of a dissolved constituent, followed by an EDTA titration of the metal liberated from the amalgam (IbbB). The method is rapid and can be applied to multicomponent determinations. Flaschka and Sadek (64B) have investigated the constancy of the titer of dilute EDTA solutions stored in glass containers. They reported appreciable changes in concentration and recommended that such solutions be stored in polyethylene. A method specific for ammonium ion in the presence of ammonia and other alkali metal ions is based on the titration of the acid liberated when ammonium ion reacts with mercury(I1) EDTA reagent (117B) Sodium Tetraphenylboron. Many papers have appeared on the use of this reagent in alkali metal determinations. Barnard and Buechl (16B) have extended their previous bibliographies I
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on sodium tetraphenylboron. Cooper (43B)has described a simple absorbance method to test the stability of the reagent. Besides the more usual determinations, the method has been extended t o the titration of silver and thallium using high frequency methods to detect the end point (97B). A new method suitable for the determination of tetraphenylboron ion and its salts has been described by Flaschka and Sadek (63B). The salt is dissolved in acetone and excess mercury(I1)-EDTA is added. The reaction produces mercury(I1) phenyl ion, liberating 4 moles of EDTA per mole of tetraphenylboron. The liberated EDTA is back-titrated with zinc chloride. Alkali Metals. Lithium has been determined by a photometric or conductometric titration with Cu(C104)2 (129B). The titration is carried out in cyclohexanone or acetone. and as little as 10-9 of lithium can be titrated with little interference from sodium or potassium. The reaction of tetraphenylborate with mercury(I1)-EDTA reagent, followed by a back-titration of the liberated EDTA forms the basis of a new rapid titrimetric method (54B, IlYB). Potassium has been determined by precipitation of 5Cd2Fe(CI\')o. KJ?e(CN), with excess standard ferrocyanide (79B). The excess was backtitrated with standard zinc sulfate, but the accuracy must be questioned on the grounds of reproducibility of the composition of the precipitate. Indirect complexometric analysis has been applied to the determination of sodium and potassium. Sodium has been separated as the zinc uranyl acetate followed by titration of the zinc (IOIB, Id3B); potassium has been separated by nitrocobaltate(II1) precipitation with an ensuing cobalt titration (IbgB, 131B). The extractive separation of lithium and sodium chlorides by 2ethyl-1-hexanol has been investigated (14bB). Silver nitrate titrations gave good results, and it was shown that sodium chloride could be quantitatively separated from uranium chIoride. The authors predicted similar separations of potassium and sodium chlorides on the basis of solubility data. Aluminum. After a thorough study (41B) Eriochrome Black T was recommended for the indirect complexometric determination. It is necessary to boil to stabilize the aluminum chelate, and also to carry out the back-titration with zinc chloride a t 10' C. to secure a reversible end point. Titanium, manganese, calcium, and magnesium can be removed' by passage of the chelated solution through a cation exchanger. Iron and copper appear in the effluent with the aluminum, and in such cases it is necessary to add triethanolamine, boil, back-titrate, then add sodium fluoride, boil, and finally back-titrate
the EDTA equivalent to the aluminum. Xylenol Orange has been recommended for the EDTA back-titration a t p H 5 (67B). Aluminum has been determined by a direct titration with sodium fluoride a t p H 4.5 using salicylidene-o-aminophenol as a fluorescent indicator (66B). Arsenic. A direct titration of arsenate in ammoniacal solution with magnesium sulfate uses Eriochrome Black T as indicator in the presence of EDTA and potassium cyanide (12B) but the results were somewhat lower than the usual iodometric assay. An indirect determination involves separation of quinoline arsenimolybdate [ ( C ~ H ~ N ) ~ H . & 12110Osj SO~. (91B) followed by solution of the precipitate in excess base. One mole of arsenic is equivalent to 26 moles of acid in the back-titration. Results good to 0.01 mg. were obtained on quantities of arsenic up to 10 mg. Rao and Rao ( I l b B ) have performed direct titrations of arsenite with potassium permanganate and ceric sulfate using iodine monochloride as catalyst. A second paper (11SB) deals with the reaction of arsenite with ferric alum in the presence of iodine monochloride or osmium tetroxide. The ferrous iron formed is titrated with sodium vanadate using diphenylamine indicator. A direct oxidimetric titration of arsenite and antimonite in alkaline solution ($OB)uses sodium hypochlorite with brazilin as indicator. Beryllium. A new method for the determination in beryl (6B) uses a phosphate separation in the presence of EDTA followed by a bismuth perchlorate titration of the dissolved precipitate. Bismuth. Busev (35B) has proposed 1-(2-pyridylazo)-2-naphthol as a highly specific indicator for the E D T A titration a t p H 1. A direct precipitation titration with diethyl dithiophosphate (7OB) in the presence of thiourea is selective in the presence of most elements of groups I through V. Cadmium. A number of indirect procedures have been proposed. Diethyldithiophosphoric acid will give a selective separation of cadmium and zinc from groups I to I11 (36B). The precipitate is analyzed by gravimetric or titrimetric procedures. Precipitation with 2-o-hydroxyphenylhenzoxazole is the basis of a sensitive method (66B). One mole of precipitate consumes 50 equivalents in the ensuing potassium permanganate titration. SOdium p-aminobenzoate has also been used as a selective precipitant (105B). The precipitate is dissolved in hydrochloric acid and the amino acid determined bromatometrically. Calcium. Belcher, Close, and West (18B) have made a critical study of the
complexometric titration of calcium in the presence of magnesium. Acid Alizarin Black SN was recommended as the indicator for the EDTA titration when calcium was present in a twelvefold excess over magnesium, and Calcon was recommended in cases where the ratio was more unfavorable. The range of application of Acid Alizarin Black SN could be extended if 1,2dianiinopropane - N,N,h”,X’ tetraacetic acid was used in place of EDTA. A new fluorescent indicator, 3’,6’dihydroxy - 2’,4’ - bis - bis(carboxyniethy1)aniinomethylfluoran has been used for the ultramicro EDTA titration (141B). Barium and strontium are cotitrated but a twentyfold excess of magnesium does not interfere. Calcium has been determined by a conductometric titration with potassium oxalate (101B). The titration is carried out in an ammoiiiacal medium in the presence of Magneson I1 to complex magnesium. Cerium. A new highly specific determination is based on the quantitative reduction of cerate by manganous ion in hot 0.2 to 0.4,V sulfuric acid ( 9 6 s ) . The lInO(OH)2 equivalent is then determined by a complexometric or by a hydroquinone titration. Titration of cerium(II1) with potassium ferrocyanide precipitates KC‘eFe(CIf), (57B). The disappearance of the starch iodine is used to mark the end point. Results accurate to 0.3yc were obtained for 5- to 95-mg. amounts of cerium. Chromium. A new volumetric method involves oxidation of chromic ion by silver nitrate (74B). After filtering off the reduced silver, the chromate is reduced with ferrous iron, the excess being determined by a potassium permanganate back-titration. The method is good for quantities of chromium from 4 t o 90 mg. A simple accurate method for determining chromium in chromite has been proposed by Usatenko and Klimkovich ( 1 S d B ) . Sintering the ore oxidizes the chromium to chromate for the final ferrous sulfate titration. Cobalt. A method useful for iron alloys separates the cobalt by precipitation as C O ~ ( ” ~ ) S ( A S O (127B). ~)~ The precipitate is dissolved in a potassium iodide solution and the liberated iodine is titrated. A procedure in which the cobalt is separated as K3Cogives good results a t the microgram level (16B). The precipitate is dissolved in sodium hydroxide, ferrous sulfate is added, and the excess is backtitrated. Precipitation with acridine and ammonium thiocyanate, followed by an EDTA titration of separated cobalt, has been used for steel analysis
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U4W.
Copper. A direct titration with ascorbic acid using 2,6-dichlorophenolindophenol as indicator has been used to analyze copper metals and bronzes
(4.9B). The results were stated to be as good as those obtained by the usual iodometric procedure. An indirect method precipitates the coppei with Co(NH&Cb in the presence of excess sodium thiosulfate. The excess thiosulfate was determined iodometrically (161B). Results good to 0.470 were obtained, but silver, zinc, cadmium, mercury, bismuth, and lead interfere. A new method used for ores precipitates (NH4)2CuFe(CN)sby the addition of excem ferrocyanide (80B). The excess is back-titrated with zinc sulfate using diphenylamine indicator in the presence of ferricyanide. Results good to 0.2570 were reported. Germanium. Ammonium molybdate with quinoline or pyridine has been used to precipitate germanium as a heteropoly compound. The precipitate on dissolution in cwess sodium hydroxide and back-titration with hydrochloric acid gives results good to 0.1 mg. (12iB). Halides. Fluoride has been determined in a number of inorganic compounds by an acidimetric titration after a pyrolytic separation (62B, 64B, 106B). Accuracy of up to 0.1% is reported. A turbidimetric titration procedure uses calciuni chloride or thorium nitrate as titrant, and is suitable for milligram quantities of fluoride (SdB). However, many common anions interfere in the procedure. The reaction of fluoride with boric acid has been used for a conductometric titration (60B). The reaction produces hydroxytrifluoroborate and sodium tetraborate. The sodium tetraborate is titrated ryith hydrochloric acid in the presence of ethyl alcohol. hlohr’s method for chloride determination has been critically examined (19B) and the interferences considered. Oxidation-reduction adsorption indicators have been used in the argentimetric titration of halides (95B) with good results. A precipitation exchange reaction with insoluble mercuric iodate allows a microdetermination of each of the halides (46B). ilfter filtering off the insoluble mercuric salts, the iodate in the filtrate, equivalent to the halide, is determined. Indium. A direct titration of 5to 20-mg. amounts with sodium ferrocyanide using diphenylamine indicator precipitates Ir4[Fe(CN)& (44B). Citric acid functions as a masking agent for some metals, but copper, nickel, chromium, iron, and thallium interfere. Iron. An improvement has been made in the classical procedure by use of a preliminary ceric titration with cacotheline indicator to remove the excess stannous reductant (68B). The ferrous iron is then determined with a dichromate or ceric titration. Diphenylaminesulfonate has been sug-
gested as a warning indicator in the ceric titration of iron with ferroin (6SB). The warning in no way interferes with the accuracy of the titration. Jankovits (71B) has titrated ferric iron with tripolyphosphoric acid a t pH 2.5 using Variamine Blue as indicator. The numerous interferences, however, indicate a restricted use of the method. The EDTA titration of ferric iron has been studied and good results obtained using Eriogreen Bas indicator in the presence of ammonium thiocyanate (14SB). Lanthanides. Lanthanum has been determined by a precipitation titration with potassium ferrocyanide (58B), the disappearance of the starch-iodine color being used to mark the end point. While the method is far from specific, 0.3% accuracy was obtained for quantities of 2 to 33 mg. of lanthanum. Praseodymium has been determined in the presence of other cerium group elements. One method uses an oxalate separation. The precipitate is ignited and the actiye osygen in the praseodymium oxide is determined by iodometry (94B)’
A second indirect method requires ignition of the nitrate salts. The Prz03 2Pr02 formed is treated with manganous sulfate solution and the permanganate formed is titrated \I ith o.ualate (SB). Cerium over 1% interferes but it can be removed by precipitation with excess ammonium nitrate. Cheng (39B) has proposed 1-(2-pyridylas an indicator azo)-%naphthol (P24S) for the EDTA titration of micro quantities of the lanthanides. The first titration of lutetium is also reported. A microvolumetric method uses paper chromatography to separate the individual rare earths before EDTA titration (SSB). Thorium and other trivalent elements in amounts up to 27, are separated and do not interfere in thc procedure. As little as 0.2% of rare earths in thorium has been determined (S4B). Excess EDTA is back-titrated with lanthanum nitrate a t pH 4.6 using a photometric Alizarin Red S end point. Hydroxylamine hydrochloride is necessary to prevent autosidation of the cerous-EDTA complex. Lead. An indirect method precipitates lead with Co(h’H3)&13 in the presence of excess sodium thiosulfate. The excess of sodium thiosulfate was determined iodometrically (151B). Results good to 0.3% were obtained but copper, silver, zinc, cadmium, mercury, and bismuth interfere. Nickel diethyldithiophosphate has been used for the precipitation titration of lead to a visual end point, but heavy metals interfere (S6B). Micro quantities of lead in metallic indium have been determined by an extractive titration *with dithizone (137B) and dithizone has been used as the indicator in a microtitration of lead with EDTA (78B). VOL. 32, NO. 5, APRIL 1960
257
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Manganese. The classical Volhard method has been studied (98B). A large excess of the solid zinc oxide buffer should be avoided m it tends to adsorb manganous ion. A large excess of zinc salt is necessary to prevent adsorption of the manganous ion by the precipitated manganese dioxide. Manganese has been determined by a precipitation titration with potassium ferrocyanide, using 3,3’dimethylnaphthidine in the presence of ferricyanide as an oxidation reduction indicator (118B). An iodcmetric method involves the reduction of manganese(VI1) to (Iv) with potassium iodide a t pH 8 to 10 in a boric acid-borax buffer. The liberated iodine is titrated nith arsenite using starch as indicator (13B). Mercury. The direct titration of mercurv(1) by permanganate has been described. Issa, Khalifa, and Hamdy (G9B) carried out the titration in a sulfuric acid medium in the presence of sodium fluoride to a pink end point. Manganese (111) was formed, and the results were within 0.5% of the chloride method if the mercury was less concentrated than 0.005N. Rao, Rao, and Rao (If 1B) carried out a similar titration using an iodine monochloride catalyst in a hydrochloric acid medium. The end point n-as marked by the disappearance of the iodine color from a carbon tetrachloride layer. Thiosemicarbazide has been used for the direct titration of mercury(I1) using copper nitrate as indicator (77B). The specificity of this reaction is illustrated by the use of thiosemicarbazide t o mask mercury in the EDTA titrations of zinc, cadmium, bismuth,, and lead (76B). A direct selectivc titration nith thiourea using diphenplcarbazide or 2-nitros-1-naphthol gives r e d t s good to 0.2% (150B). A microvolumetric method separates mercury(I1) from zinc and cadmium by precipitation with thioanalide. The precipitate is dissolved in acid and potassium iodate is added. The excess iodine is back-titrated with thiosulfate (4ZB). Molybdenum. The various volumetric methods have been compared, and i t is suggested t h a t the reduction of molybdenum(V1) to (V) with bismuth or mercury gives better results than the reduction of molybdenum(V1) to (111) with zinc (LB). A silver reduction has been used to reduce molybdenum(VI) to (111) in hydrochloric acid. Titration with dichromate using diphenylamine as indicator gave results accurate to 0.1% for 250 mg. of molybdic oxide (144B). A direct precipitation titration of molybdate with a lead salt a t pH 6 (82B, 109B) uses 4-(Zpyridylazo) resorcinol (PAR) to indicate the first excess of lead. An alternate method of indication uses copperEDTA and PAN. The first excess of lead displaces copper from the EDTA 258 R
ANALYTICAL CHEMISTRY
complex, and the copper combines with the PAN, but other metals that combine with EDTA will interfere. Results good to 0.02 mg. of molybdenum were obtained. A conductometric titration of ammonium molybdate with potassium ferrocyanide precipitates Kz(MoO*)Fe(CN)b. An accuracy of 0.7% for 2 to 43 mg. of molybdenum was obtained (56B). Nickel. Nitroso-R salt has been used to mask cobalt in the photometric EDTA titration (SIB). Nickel has been determined in iron alloys by precipitation of Nia(NH4)&04, followed by an iodometric determination of the precipitated arsenate (126B). A preliminary arsenate precipitation from an acetic acid solution is necessary to separate the iron. A microvolumetric method precipitates the nickel from an ammoniacal solution with hexavanadic acid (135B). The Ni(NHS)4VsOleprecipitate is dissolved in acid, and the vanadium is titrated with Mohr’s salt. Palladium. Picolinic acid and quinaldinic acid have been used in the separation and volumetric determination. The precipitate can be dissolved in excess potassium cyanide, the excess being back-titrated with silver nitrate (86B), or the precipitate can be dissolved in excess K2Ni(CN)4 solution and the liberated nickel titrated with EDTA (87B). The method is selective in the presence of a large number of metals. Beamish (f7B)has critically reviewed the volumetric methods for palladium and the other platinum metals. Scandium. A photometric EDTA titration procedure gives good results in the presence of large quantities of rare earth elements (55B). The course of the titration is followed by the absorb ance of the copper-EDTA complex. Silicon. Silicic acid reacts with excess ammonium molybdate in an aciil solution to form a complex which can be quantitatively reduced with potassium iodide. The liberated iodine is extracted and titrated with thiosulfate (134B). The method has been used on a variety of samples including titanium dioxide, silicon dioxide, tungstic oxide, and steels. The reaction of silicomolybdic acid with 8-quinolinol has been used to determine silica in glass with results within 0.2y0 of the classical method (108B). The excess 8-quinolinol is determined bromometrically in the filtrate. Silver. Titration with ferrous sulfate in a buffered acetate solution containing fluoride reduces silver nitrate to the metal (60B). Using Variamine Blue as indicator, results good to 0.2% were obtained even in the presence of copper. If interfering ions are present, the silver can be separated by a prior reduction to the metal. Titration with sodium nitroprusside gives reproducible
.but slightly high results (f28B). The bilver nitrate solution must be titrated into the reagent, and a good end point is obtained with or without eosin as adsorption indicator. Tbe method can be used in tbe presence of lead and zinc. Sulfur. Sulfides have been determined by direct titration with o-hydroxymercuribenzoic acid using sodium nitroprusside (147B), or thiofluorescein or dithizone (148B)as indicator. The method is selective in that halides, thiocyanate, thiosulfate, and sulfate, among others, do not interfere. A new method for trace sulfur in nickel and steel ( S a ) uses a hydriodic acid distillation to free hydrogen sulfide which is collected and titrated w-ith potassium iodate. The method is said to be a suitable alternative to the more usual procedures. Bakacs (11B) has used the Eriochrome Black T-magnesium complex a s indicator in the titration of sulfate with barium chloride. Excess barium displaces magnesium from the complex to give a color change. A carbon tetrachloride phase is used to collect the precipitated barium sulfate. Selenium. ZaikovskiI (152B; has determined selenium(1V) in dilute nitric acid by the addition of excess standard ascorbic acid followed by a back-titration with iodine. d new method for small quantities involves separation of elemental selenium by reduction with sulfur dioxide. The precipitate is treated with sulfuric acid and forms SeSOs which decomposes rapidly, liberating the metal. The metal is determined by the addition of excess permanganate and back-titration with Mohr’s salt (101B). Tellurium. -4new method involves reduction to the metal by lactose. The reduction is rapid and complete a t boiling temperatures, and the finely divided tellurium is titrated directly with dichromate in acid solution (99B). Thallium. Sodium tetraphenylboron has been used for the conductometric precipitation titration of thallium(1) (146B). Values were slightly higher than calculated, and no attempt was made to study interferences. High frequency (133B) methods have also been used to detect the end point in the titration. A study has been made of metallic reductors suitable for reducing thallium(II1) to (I) (116B). I n dilute sulfuric acid, bismuth, cadmium. and silver were found suitable and the reduced thallium was titrated with potassium bromate in the presence of hydrochloric acid. The precipitated thallium chloride dissolved as the titration proceeded. Thorium. The marked interest in this element is reflected in the many EDTA procedures that have been published.
Pribil and Koros (IOrB), after a critical investigation of the methods described in the literature, recommended Xylenol Orange a t pH 1.5 to 3,5 for the complexometric microdetermination. A method suitable for as little as 0.1% thorium in uranium alloys that may contain tungsten or titanium uses lanthanum as a carrier in the fluoride separation of the thorium (fL6B). After dissolution the precipitate is titrated with EDTA. A direct photometric titration procedure using EDTA with Alizarin Red S indicator allows the determination of as little as 0.1% thorium in rare earths without preliminary separation (S4B). The titration must be carried out rapidly a t p H 2.4 to 3.4. A photometric titration with sodium tri- or pyrophosphate solution uses alizarin at pH 4 to 5 or aluminon a t pH 6 to 8 as indicators ( I SOB). Tin. A procedure has been developed for the analysis of copperbaee alloys (75%). Tin(I1) and (IV) are complexed in acid solution with excess EDTA. The excess is backtitrated with zinc employing 3,3'dimethylnaphthidine as an oxidationreduction indicator in the presence of traces of ferri-ferrocyanide. Tin is then displaced with fluoride and the backtitration continued. An ascorbimetric determination whose accuracy is comparable to other methods has been proposed (QOB). The tin is separated as the metal by aluminum or zinc reduction, then dissolved in hydrochloric acid. The tin(I1) is then oxidized with excess ferric chloride a t the boiling temperature, and the excess ferric chloride titrated with ascorbic acid. Titanium. A diffwential titration uses a zinc amalgam reductor to give titanjum(II1) and iron(I1) in solution. T h e titanium is then titrated \$ ith permanganate to the disappearance of the blue color given by a sodium tungstate indicator, then the titration is continued to a pink end point for iron (7SB). Veselago has carried out a similar ceric titration using cacotheline indicator for titanium, then adding phenylanthranilic acid for the iron titration (156B). An indirect procedure separates the titanium by precipitation with sodium arsenate a t 80" C. from a solution made just yellow to methyl orange by sulfuric acid ( f 2 b B ) . The precipitate was dissolved in potassium iodide solution and the liberated iodine titrated. Tungsten. A direct precipitation titration of tungstate similar t o t h a t described for molybdate uses PAR or copper-EDTA with PAN t o indicate the end point (82B, I 1 OB). The titration is best carried out a t 100" C. using a hexamethylenetetramine buffer, pH 4 to 5. Results were good for quantities of tungsten from 2 t o 8 mg. A rapid analysis of ferrotungsten uses
reduction of the tungsten with amalgamated lead in a carbon dioxide atmosphere before titration with copper sulfate to a brilliant yellow end point (1S9B). Uranium. Rao and Rao (1l4B) have studied the cerimetric determination of uranium(1V) and recommended Erioglaucine, Eriogreen, or Xylene Cyano1 FF as indicators preferable to the ones more commonly associated with the use of ceric sulfate. Titanous sulfate has been used as a reductant before the oxidimetric titration of uranium (lS8B). Interfering elements were separated by a cupferron precipitation, and copper sulfate was ueed to indicate complete reduction of the uranium. The first excess of titanous sulfate precipitated metallic copper, which was redissolved by the addition of excess mercuric perchlorate. Analytical data were presented to show that the method compares favorably with the standard zinc amalgam reduction. A number of papers deal with the determination of uranium in the presence of other elements. Molybdenum does not interfere in the lead reductor method if perchloric acid is absent (S7B). Tungstate ion interferw in the Jones reductor method but it can be precipitated and removed by fuming with sulfuric acid (45B). Anion exchangers retain uranium(VI) and allow separation from iron(I1) and vanadium (IV) ( 6 f B , 9SB). Bismuth can be removed by evaporating the uranium solution to dryness in the presence of bromine and hydrogen bromide (9SB). An indirect determination precipitates U04.2H40 from a dilute nitric acid solution with excess hydrogen peroxide (1B). The precipitate is dissolved in sulfuric acid and the liberated peroxide titrated with permanganate. A prior separation of uranium is necessary to avoid the interference of a number of constituents. Similarly, hydrogen peroxide has been used to mask uranium(V1) in the EDTA titration a t pH 10 (81B). Vanadium. Ascorbic acid and ferrous salts have been used for the reductometric titration of vanadium(V) (47B). Results good to 0.1% were reported for 50- to 200-mg. amounts of vanadium pentoxide. A microiodometric determination employs the reaction of vanadium(V) with potassium iodide in the presence of mannitol ( I OOB),the liberated iodine being titrated with thiosulfate. An error of 1.5y0 was reported for 50-7 amounts of vanadium. Zinc. Xylene Blue XS and Patent Blue V have been recommended as reversible oxidation reduction adsorption indicators in the ferrocyanide titration (SOB). The titration is carried out in neutral or weakly acid solution a t 100" C., but in the presence of ammonium salts it is necessary to add
excess ferrocyanide and back-titrate at 60" C. A volumetric method as accurate as the ferrocyanide, but still subject to many interferences,' involves the reaction of zinc with an alkaline citrate solution. An equivalent of acid is liberated and back-titrated (10SB) Zirconium. Solochrome Viclck l? has been recommended as indicator for the micro- or macrotitration of zirconium with EDTA (75B). The titration is carried out in hot normal hydrochloric acid. An indirect determination in ores precipitates the zirconium as iodate from a sulfuric acid solution (4OB). The precipitate in dissolved in a potassium iodate solution and the liberated iodine is titrated. The 'coniposition of the iodate precipitate would appear to depend on the time of standing. Precipitation with mandelic or pbromomandelic acid from 6N hydrochloric acid gives precipitates of uniform composition. The precipitates are dissolved in sodium carbonate solution and the organic precipitant is determined with permanganate or dichromate titration ( I Z l B ) . LITERATURE CITED
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493A) Wilson, R. F., Womack, C. M. Jr., J . Am. Chem. Soc. 80,2065-6 (1958). (94A) Yatsimirskii, K. B., Kharitonov, V. V., Trudy Zvanovsk. Khina. Teknol. Znst. No. 5, 6-15 (1956). (95A) Yen, J-Y., Djao, K-H., Hsiao, F. C., Pei Ching T u Hs&h Hszieh PaoTzu Jan K’o HsGeh 4,195-9 (1958).
Volumetric (1B) Alexa, J., Chem. listy 51, 2254-8 (1957). (2B) Alimarin, I. P., Gibalo, I. M., Zavodskaya Lab. 23, 412-6 (1957). (3B) AmbrozhiI, M. N., Gol’tsev, A. M., Nauch Doklady Vysskei Shkoly Kham. I Khim. Teknol. 3, 491-4 (1958). (4B) Ankudinova, E. V., Petrashen, V. I., Trudy Novocherkas, Politekh. Znst. 41, 3-10 (1956); Referat. Zhur. Khim. No. 23438 (1957). (5B) Athavale, V. T., et al., Proc. UN Intern. Conf. Peaceful Uses Atomic Energy, 2nd Geneva 3, 554-60 (1958). (6B) Bagbanly, I. L., Doklady Akad. Nauk Azerbaidzham. S.S.R. 12, 639-42 (1956). (7B) Bagbanly, I. L., Guseinov, I. K., Ibid.. 14. 515-18 (1958). (8B) dagbanly, I. L., hlamedkulieva, M. M., Ibzd., 14,997-1001 (1958). (9B) Bagbanly, I. L., Mirzeova, T. R., . Uchenye Zapisi Azerbaidzhan. Gosudarst. Univ. im. S . M . Kirova 4, 35-44 (1957). (10B) Bagbanly, I. L., Mirzeova, 1. R., Doklady Akad. Nauk Azerbaidzhan. S.S.R. 14, 849-52 (1958). (11B) Bakacs, E., Magyar Kem. Folyoirat 61, 48-50 (1955). (12B) Bakacs, E., Szekeres, L., Lang, B., 2. anal. Chem. 158. 14-20 (19571. (13B) Bapat, M. G.; Sharma, B.; Zbid., 157, 261-3 (1957). (14B) Barnard, A. J., Broad, W. C., Flaschka, H., Chemist Analyst 46, 106112 (19571: 47. 22-28, 52-56, 78-84, iog-in (iQ58).’ (15B) Barnard, A. J., Buecld, H., Ibid., 47, 46-7 (1958). (16B) Bartha, L., Gorog, S., Talanta 1, 310-13 (1958). (17B) . . Beamish, F. E., Anal. Chim. Acta 20, 101-112 (1959): (18B) Belcher, R., Close, R. A., West, T. S., Talanta 1, 238-44 (1958). (19B) Belcher, R., MacDonald, A. M. G., Perry, E., Anal. Chim. Acta 16, 524-9 (1957). (20B) Bitskei, J., Acta Chim. Acad. Sci. Hung. 10,313-26 (1957). (21B) Bobtelsky, M., Cohen, M. M., Anal. Chim. Acta 20, 1-15 (1959). (22B) Bobtelsky, M., Eisenstadter, J., Ibid., 16, 479-487 (1957). (23B) Ibid., pp. 503-11. (24B) Ibid., pp. 579-87. (25B) Ibid., 18, 534-40 (1958). (26B) Ibid., 2 0 , 216-27 (1959). (27B) Zbid., pp. 352-57. (28B) Bobtelsky, N., Rafailoff, R., Ibid., 16, 458-92 (1957). (29B) Ibid., 17,267-70 (1957). (30B) Bognar, J., Xagy, L., Magyar Kem. Folyoirat 62, 217-20 (1956). (31B) Brake, L. D., McNabb, W. M., Hazel, J . F., Anal. Chim. Acta 17, 314-17 (1957). (32B) Brandt, W. W., Duswalt, A. X., ANAL. CHEM. 30, 1120-2 (1958). (33B) Bricker, C. E., Schonberg, S. S., Zbid., 30, 922-8 (1958). (34B) Bril, K. Y Holzer, S., Rethy, B., Ibid., 31, 1353-7 (1959). (35B) Busev, .4 I., Zhur. Anal. Khim. 12, 386-9 (1957). (36B) Busev, A. I., Ivanyutin, hf. I., Zbid., 13, 312-18, 647-52 (1958). (37B) Byrne, J. T., Larsen, hi. K., Pflug, J . L., ANAL.CHEX.31, 942-5 (1959).
(38B) Cerrai, E., Testa, C., Energia nucleare (Mzlan) 5, 824-30 (1958). (39B) Cheng, K. L., Chemist Analyst 47, 93-4 (1958). (40B) Chernikhov, Y. A., Kuchmistaya, G. I., Zavodskaya Lab. 23, 14-18 (1957). (41B) Cimerman, C., Alon, A., Mashall, J., Talanta 1, 314-28 (1958). (42B) Cimerman, C., Frenkel, S., Anal. Chzm. Acta 16, 305-11 (1957). (43B) Cooper, S.S., Chemist Analyst 46, 62-4 (1957). (44B) Deichman, E. X., Tananaev, I. V., Zhur. Anal. Khzm. 13, 196-200 (1958). (45B) Dufour R. F., Artiolo, O., Nuclear Sei. Abstracts 13,N o . 548 (1959). (46B) Erdey L., Banyai, E., Paulik, F , Acta &him. Acad. Sci. Hung. 13, 453-63 (1958). (47B) Erdey, L., Rodor, E., Buzas, I., Ibid., 7,27745, 287-92, 293-304 (1955). (48B) Erdey, L , Polos, L., Anal. Chim. Acta 17, 458-62 (1957). (49B) Erdev, L., Siposs, G., Z . anal. Chem. 157, ‘166-77 (1957). (50B) Erdey, L., Vigh, K., Ibid., 157, 184-92 (1957). (51B) Fisher, S., Kunin, R., ANAL. CHEY. 29, 400-402 (1957). (52B) Flaschka, H., Talanta 1, 60-76 (1958). (53B) Flaschka, H., Sadek, F., Chemist Analyst 47, 30-1 (1958). (54B) Flaschka, H., Sadek, F., 2. anal. C h a . 156,23-8 (1957). (55B) Fritz, J. S., Pietrzyk, D. J., ANAL. CHEM.31, 1157-9 (1959). (56B) Fujita, Y., Nippon Kagaku Zasshi 78, 1757-61 (1957). (57B) Ibid., pp. 1761-4. (58B) Ibid., 79, 1256-9 (1958). (59B) Gagliardi, E., Reimers, H., Z . anal. Chem. 160, 1-6 (1958). (60B) Gol’dinov, A. L. Lukhovitskii, V. I., Gorovits, M. Roginskaya, B. S., Zhur. Anal. Khim. 13, 583-5 (1958). (61B) Golovatyi, R. N., Shindel, R. E.,
A.,
Nauch. Zap iski L’vov. Torgmo-Ekonom. Inst. 1, 261-70 (1954); Referat. Zhur. Khzm. Yo. 7078 (1956). (62B) Haff, L. V., Butler, C. P., Bisso, J. D., ANAL CHEM.30,984-9 (1958).
(63B) Heumaiin, W. R., Belovic, B., Ibid., 29, 1226-7 (1957). (64B) Hibbits, J. O., Ibid., 29, 1760-2 (1957). (65B) Holzbecher, Z., Chem. listy 52, 430-8 (1958). (66B) H6riud6, Y., Saito, RI., Nippon Kagaku Zasshi 77, 1340-4 (1956). (67B) Houda, M., Korbl, J., Bazant, V., Pribl, E.., Chem. listy 51, 2259-65 /,rlz-\ (lYdI).
(68B) Hume, D. S . , Kolthoff, I. hl., Anal. Chim. Acta 16, 415-18 (1957). (69B) Issa, I. hl., Khalifa, H., Hamdy, hl., Ibid., 16, 301-4 (1957). (70B) Ivanyutin, RI. l., Busev, A. I., n’auch Dokltcdy Vysshei Shkoly, Khim. i Khim. Teknol. No. 1, 73-8 (1958). (7lB) Jankovits, L., Acta Chim. Acad. Sci. Hung. 11, 185-94 (1957). (72B) Kinnumen, J., Wrnnerstrand, B., Chemist Analyst 46, 34 i.?.957). (73B) Kobayashi, S.,Og.tsawara, I., Rep. Gov. Chem. i n d . Research Inst. Tokyo 52, 21-24 (1957). (74B) Komatsu, S., Hiroaki, Z., Sippon Kagaku 2as:;hi 77, 1166-9 (1956). (75B) Korbisch, J., Farag, A., 2. anal. Chem. 165,6-10 (1959). (76B) Korbl, J., Pribil, ,J., Chma. listy
51, 667-71 J1957). ( V B ) Koshkin, N. V., Zhur. Anal. Khim. 13,308-10 (1958).
(78B) Kotrly, S., Chem. listy 51, 730-4 (1957). (79B) Koslov, A. S., Zavodskaya Lab. 23, 157-9 (1957). (SOB) Koslov, A. S., Bageev, V. V., Nauch. Doklady Vysshei Shkoly, Khim. i Khim. Teknol. No. 2, 300-4 (1958). (81B) Lassner. E.. Scharf. R..’ 2. anal. ’ Chem. 159, 2 1 2 4 (1958):
(82B) Lassner, E., Scharf, R., Puschel, R., Ibid., 165,29-32 (1959). (83B) Lauer, R. S., Poluektov, N. S., Zaaodskaya Lab. 25, 391-6 (1959). (84B) Luke, C. L., ANAL. CHEM. 29, 1227-8 (1957), 31 1393-4 (1959). (85B) Majumdar, K., Chakrabarthy, N. M., Z . anal. Chem. 156,103-5 (1957). (86B) Rlajumdar, A. K., Sen Gupta, J. G., Zbid., 161,179-81 (1958). (87B) Ibid., pp. 181-3. (88B) Majumdar, A. K., Singh, B. R., Zbid., 156, 265-8 (1957). (89B) Ibid., 161, 257-60 (1958). (9OB) hlarta, S. S., Riri, Z., Analeleuniu.
A.
“C. I . Parhon” Bucuresti, Ser. stiint. nut. No. 10, 39-50 (1956). (91B) hleyer, S., Koch, 0. G., Z . anal. Chem. 158, 434-8 (1957). (92B) Miller, W. E., ANAL. CHEM.30, 1462-4 (1968’1. (93B) Milner, G. W. C., Barnett, G. A., Anal. Chim. Acta 17,220-5 (1957). (94B) Misumi, S., Ni’pGon . Kagaku Zasshi . 77, 786-8 (1956’). (95B) Mora. G. A.. Anales uniu. Murcia . (Spain) 15, 121-223 (1956-57). \ - - - - I
~
(96B) Mraa, L., Siman, V., Zyka, J., Chem. listy 51, 1828-31 (1957). (97B) Mukherji, A. K., Sant, B. R., ANAL.CHEX 31, 608-10 (1959). (98B) Oka, Y., Kanno, T., Nippon Kinzoku Gakkishi 18, 552-6 (1954). (99B) Onufrienok, I. P., Akaenenko, V. M., Zhur. Anal. Khim. 13, 119-22 (1958). OOB) Pais, I., Magyar Kem. Folyoirat 62, 252 (1956). 01B) Pasovskaya, G. B., Trudy Komiss. Anal. Khim., Akad. Nauk S.S.S.R. 7. 272-5 (19561: Referat. Zhur. Khim. SO.121811957j. “ 02B) Patsuk, A. A., Zhur. Anal. Khim. 12. 230-5 119571: J. Anal. Chem. U.S.S.R. 12,‘229-3’(1957). (103B) Pavinlova. A. V.. Bernshtein. B. I., . A‘auk. Zapiski ‘ Chekiuets’k Univ. 11 107-12 (1955). (104B) Pilleri, R., Z. anal. Chem. 157, 1-2 (1957). (105B) Portnov. A. I.. Vasvutinskii. A. I.. . Zhu;. Anal. k h i m . 13,3%-22 (1958). ’ (106B) Powell, R. H., Menis, O., ANAL. CHEM.30, 1546-9 (1958). (107R) Pribil, R., Koros, E., Magyar Kem. Folyoirat 64,55-7 (1958). (108B) Pukas, T., Grabinska, K., Zeszyty Nauk. Politech. Slask. Chem. No. 2,
93-6 (1957). (109B) Puschel, R.,Lassner, E., Scharf, R., 2. anal. Chem. 163, 104-10 (1958). (llOB) Ibid., pp. 344-9. (111B) Rao, G. J., Rao, K. H., Rao, G. G., Zbid., 160, 114-7 (1958). (112B) Rao, K. B., Rao, G. G., Z . anal. C h m . 155, 161-5 (1957). (113B) Ibid., 157, 96-100 (1957). (111B) Rao, I’., Rao, G. G., Talanta 1, 355-8 (1958). (115B) Reilley, C. N., Schmidt, R. W., ANAL.CHEM.31, 887-97 (1959). (116B) Rolf, R. F., Lieninger, E., Ibid., 31, 425-6 (1959). (117B) Sadek, F. S.,Reilley, C. N., Ibid., 31, 494-8 (1959).
(118B) Sajo, I., Magyar Rem. Folyoirat 61,196-8 (1955). (119B) Ibid., 62, 56-9 (1956): (120B) Zbid., pp. 176-7. (121B) Schneer, A., Hartmann, H., Zbid., 63, 295-6 (1957). (1223) Scribner, W. G., Reilley, C. N., ANAL.CHEM.30. 1452-62 (1958). (123B) Sen, B., ’2. anal. ’ C h h . 157, 2-6 (1957). (124B) Shakhova, Z. F., Motorkine, R. K., Vestnik Moskov. Univ. 12, Ser. Mat., Mekh., Astron., Fiz. i Khim. KO. 2, 183-93 (1957). ‘ (125B) Shakhtakhtinskii, G. B. Mukimov, A. M., Doklady Akad. Nauk Azerbaidzhan S.S.S.R. 13,629-32 (1957). (126R) Shakhtakhtinskii, G. B., Turchinskii, M. L., Trudy Azerb. Ind. Inst. 11. 64-9 (1955): Referat. Zhur. Khim. NO.61483 (1956). (127B) Ibid., 11, 70-5 (1955); ‘Referat. Zhur. Khim. No. 68714 (1956). (128B) Spacu, P:, Pirtei, T.’ I., Rev. chim. (Bucharest) 7, 481-3 (1956). (129B) Specker, H., Hartkamp, H., Jackworth, E., Z. anal. Chem. 163, 111-9 (i958j. ‘ (130B) Susuki, S., Mitsuma, O., Sugano,. T.. J . Osaka Inst. Scz. Technol. (Kznkz U&.) 4 21-9 (1958). (131B) Taketatsu, T., Nippon Kagaku Zasshi 78, 640-2 (1957). (132B) Usatenko, Y. I., Klimkovich, E.
Trudy Dnepropetrovsk, Khim. k k n o l . Inst. No. 5, 156-60 (1956); Referat. Zhur. Met. No. 13649 (1957). (133B) Veiss, A., Ievens, A., Zhur. Anal. Khim. 14, 143-4 (1959). (134B) Veitsman, R. M., Zavodskaya Lab. 23, 153-7 (1957). (135B) Verdi-Zade, A. A., Trudy Azerbaidzhun. Gosudarst. Zaoch. Pedagog. Inst. 4, 77-81 (1957); Referat. Zhur. Met. No.22742 (1957). (136B) Veselago, L. I., Zhur. Anal. Khim. 12, 381-5 (1957); J. Anal. Chem. U.S.S.R. 12, 395-9 (1957). (137B) Volkova, A. I., Zakharova, N. N., Ukrain. Khim. Zhur. 23, 530-2 (1957). (138B) Wahlberg, J. S., Skinner, D. L., Rader, L. F., ANAL. CHEM.29, 954-7
(1957). (139B) Wakamatsu, S., Bunseki Kagaku 5, 347-8 (1956). (140B) Ibid., 6, 426-30 (1957). (141B) Wallach, D. F. H., Surgenor, D. M., Soderberg, J., Delano, F., ANAL. CHEY.31, 456-60 (1959). (142B) Waterbury, G. R., Van Kooten, E. H.. Morosin,. B.,. Zm., 30, 1627-9 (i958j. (143B) Wehber, P., Johannsen, W., z. anal. Chem. 158, 7-9 (1957). (144B) Weiner, R., Boriss, P., Ibid., 160, 343-51 (1958). (145B) Wendlandt, W. W., Chemist Analyst 46, 8 (1957). (146B) Willard, H. E., Mosen, A. W., Gardner. R. I).. ANAL. CmM. 30, 1614-6 (1958). ’ (147B) Wronski, M., Chem. Anal. (Warsaw) 2, 385-6 (1957). (148B) Wronski, M., Burkart, P., Faserforsch u. Teztiltech. 9, 36-7 (1958). 1149B) Wunsch., L.., Chem. listv 51, 376-8 . (1957). (150B) Yatsimirskii, K. B., Astasheva, A. A., Zhur. Anal. Khim. 11, 442-6 (1956). (151B) Yatsimirskii, K. B., Roslyakova, E. N., Sovremen. Metody Anal. c met. Sbornik 1955, 124-7; Referat. Zhur. Khim. No.29305 (1956). (152B) Zaikovskii, F. V.,Ibid., 1955, 142-6; Referat. Zhur. Khim. So.29632 (1956).
VOL. 32, NO, 5 , APRIL 1960
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