Amperometric Titrations lohn T. Stock, University of Connecticut, Storrs, Conn.
T
covers the period from Kovember 1965 (279) through October 1967. Unless otherwise indicated, potentials are with respect to the saturated calomel electrode (SCE). Both general (94, 116, 117, 271) and specialized reviews have appeared. Many of the latter emphasize biamperometric titrimetry. Stulik and Vydra have discussed electrometric titration with two polarized electrodes (284) and the determination of organic compounds by such methods (285). The analytical aspects of such electrodes have been surveyed (192). Amperometric end point methods continue to be useful in constant-current coulometric titrimetry (173, 287, 329). Other reviews concern biamperometric titrimetry in drug control work (16), the applications of organic reagents (152, 340), and water determination by the Karl Fischer reagent (5, 286, 296). Helbig (92) has discussed ultramicroanalytical electrochemical techniques. The principles of amperometric and other electroanalytical methods have been discussed (67, 82). Equations have been derived for the treatment of amperometric and other linear titrimetric curves (165, 164). Error calculations in amperometric precipitation titrations (81) and the definition of best indication methods in amperometric and other titrations (48) have been discussed. Tanaka and Kakagawa (291) have derived expressions for amperometric and other compleximetric titration curves. Biamperometric titrations in which electrode reaction kinetics are controlled by charge transfer in the solution have been examined (232), Filenko (60, 64) has studied the effects of electrode rotation on biamperometric titration curves. His work confirms the efficacy of carrying out such titrations a t two rotating electrodes (278). The mathematical formulation of the titration curves and the accuracy and sensitivity of biamperometric indication have been discussed (284). HIS PAPER
APPARATUS A N D METHODOLOGY
Available amperometric and other titrimetric equipment has been surveyed (245). An amperometric titration cell has been made from a plastic soft-drink container (28). The preparation of polyacrylamide-filled 1250) and glass (53) salt bridges has been described. From amperometric titrations with various electrode materials, Terekhova (294) found a vanadium electrode 392 R
ANALYTICAL CHEMISTRY
to be best for iron determination in the presence of copper. A. molybdenum electrode was most suited for mercury determination in the presence of copper. A plastic electrode holder for ultramicroamperometric titrimetry (165) and a n automatic buret that repeatedly delivers 0.05 to 0.2 ml of titrant (68) have also been described. An amperometric titrator that is constructed from a p H meter (288) and a simple p H meter that can be used for “dead-stop” titrimetry (104) have been reported. Severa! titration units that incorporate current amplification have been described (19, 105, 197). Coulometric titrators that stop automatically a t a given biamperometric current (247), provide a halt-restart approach to the end point (153), or permit the continuous recording of a titrand that is carried into the cell by a gas stream (22.9) have been developed. A siphon pipet, each discharge of which briefly short-circuits the electrode system, has been uqed to record amperometric titration curve5 (199). A simple automatic titrator for Karl Fischer water determination has been described (342). Tanno (2.92) ha.. developed a recording analyzer for dissolved oxygen in boiler water. The sequence of operations is performed automatically. Freese (71) has surveyed anodic amperoinetric indicator methods in complexometry. Amperometric techniques for the study of bromination reaction kinetics have been described (52, 102). The applications of amperometric titration without the application of an external emf have been extended (308). An interesting end-point method in coulometric titration involves the usual isolated counter electrode and two working electrodes, between which a small fixed potential is maintained ( 6 ) . The working electrodes then carry unequal shares of the constant current, and the smaller share is a linear function of titrand concentration. ;i large continuous indicator current is then available, since losses associated with indicator electrode electrolysis in conventional amperometry do not occur. Novak (193) has proposed a dropping mercury electrode (DNE) used in conjunction with a dropping cadmium amalgam electrode for the determination of titrands that have half-wave potentials equal to or more negative than that of cadmium. “Dilution titration,” with the chosen supporting solution, is used for high titrand concentrations, and gives a ‘[reversed L” titration curve.
Titration with a standard solution of the titrand, used for low concentrations, gives a current that rises to become constant beyond the end point. The DJIE is replaced by a n SCE for titrands such as copper. The titration curve then cuts the zero-current line at the end point. Sorensen and Sympson (274) have explored coulostatic titrations at a DAIE. The D M E potential, initially such that no faradaic current flows, is shifted by a pulse of charge so that oxidation or reduction of the titrand occurs. The relaxation data can be used to construct linear titration curves of shape resembling those obtained in amperometric titration. The analytical aspects of galvostalametry, a technique t h a t requires neither reference electrode nor expensive recorder, have been examined by Sligh and Brenner (266). The background solution containing the electroactive substance is suspended under tensile stress in the longer limb of a J-shaped evacuated glass tube. This limb has a platinum indicator electrode sealed into the top, 2nd another electrode dips into the lower part of the solution. -4constant current of a few milliamperes is passed and the time required for collapse of the suspended column is noted. This collapse is caused by gas film formation after depletion of electroactive substance at the indicator electrode. The technique gives a composite result for mixtures, and not the concentration of any one constituent. ACID-BASE REACTIONS
Twin bismuth electrodes have been used in the biamperometric titration of HCI with NaOH (108). The current sinks to a minimum at the end point. Individual acids, mixtures, and bases in 0.1N LiCl have been amperometrically titrated a t a DME (132). Mixtures of HCl and a n acid such as phthalic or acetic have been redoxokinetically titrated with XaOH in the presence of quinhydrone (134). Ruskul (255) has used ethylenediamine or diethylamine as titrant for benzoic or salicylic acid in propanolglycerol medium. With pyrogallol as electrometric indicator and a coppersaturated methanolic CuS04 reference electrode, no external emf source was required. p-Nitrophenol and 1-naphthol were titrated in propanol-formamide and methanol-formamide respectively. Benzoic acid in admixture with one of
the phenols can be titrated in forinamidefree medium. After the addition of formamide, t h e titration can be continued to determine the phenol. Amperometric titration with HC1 of oxygen in dimethylsulfoxide has been used to evaluate the diffusion coefficient of t h e hydrogen ion in this solvent (106).
PRECIPITATION AND COMPLEXING REACTIONS
M e t h o d s Involving Silver. By suitable choice of reference electrode, DhIE titrations of cyanide with a n d of silver with E D T A have been r u n without a n external emf source (99, 100). End-point phenomena in the argentornetric titration of cyanide a t a platinum electrode have been described (109, 113). Using a rotating platinum electrode ( R P E ) at zero potential, Musha and Ikeda (187) have successively titrated cyanide, chloride, and cyanate with ;IgS03. I n 0.111 KN03 a t 10’ C and pH 10, the first current increase gives the cyanide concentration. Chloride is titrated at p H 6 5 to 8 after the addition of gelatin. X e t h anol is then added and cyanate is titrated below 5” C. Thiocyanate and cyanate have been successively titrated by methanol addition after the thiocyanate point (98). Treatment FTith K C N in 50y0 isopropanolic solution, masking of excess KC?\’ by HCHO, and amperometric titration of the resulting thiocyanate with &so3 have been used to determine elemental sulfur (97). Thiocyanate has been titrated in stirred solution a t a fixed platinum electrode ( 9 ) and a t Ag-AgSCS biamperometric electrodes (66). The behavior of ;igAg2S electrodes has been studied biamperometrically (66) and these electrodes have been used in coulometric titrations of microgram amounts of sulfide (33). The amperometric indicator system silver anode-platinum cathode has been recommended for the coulometric argentometric titration of chloride in biological liquids (231). Ai chosen titrant level is generated and the sample is added. This restarts the generation, which stops when the titrant concentration regains the chosen level. Ketchum and Johnson (126) have described the microdetermination of organic chlorine or bromine by oxygen-flask combustion and coulometric titration with silver. The titration is run in the modified combustion flask. Conditions for the accurate coulonietric biamperometric titration of microgram amounts of bromide have been e,tablished (32) and end-point phenomena in iodide-silver titrimetry have been studied (112, 113). Silver in ores has been determined by retention as AgCl on a n anion exchange column, elution with NH8, and amperometric titration a t p H 2.5 to 3 with K I (122). Halogenq in cellulose prepa-
rations have been determined by fusion with potassium and final amperometric titration at a n RPE with AgXO3 (180). Mixtures of palladium and silver have been amperometrically titrated kj-ith K I (273). One aliquot of p H 1 to 2 (H2S04) gives the sum; only silver is titrated in a second aliquot of p H 4 t o 5 . D l I E amperometric indication has been recommended over potentiometric or conductometric methods in the titration of less than 0.0023f silver \\ith vanadate, or the reverse (237). With p-aminophenol as electrometric indicator, silver and cadmium have been successively titrated with Na;is02 (234). Reinecke salt has been used as an aniperometric titrant for microquantities of silver ( 8 ) . A polarograph has been used to record biamperometric currents in the Coulometric titration of tetraphenylborate (42). Barbiturates such as luminal have been biamperometrically titrated with (183). Xitrite is added as electrometric indicator. A critical study of and other amperometric titrations of sulfhydryl groups in bovine-serum albumin has appeared (136). 0.0005A\T ;3gK03 has been used in a modified Kolthoff-Harris titration of sulfhydryl in a solution made from 0.1 to 0.25 ml of serum (186). Theoretical result5 were obtained in the amperonietric titration, a t a vibrating platinum electrode, of glutathione and cysteine in an imidazole buffer of p H 6 to 7 (269). Ethanolic . i g S 0 3 has been used for the amperometric titration of thiol w e d as regulator in the emulsion polymerization of chloroprene (167). Kevei and I3lazovich (127) have determined sulfhydryl groups by addition of AgNOs to bring the current level to that in a sulfhydryl-free solution of known AgSOd concentration. The durability of polyacrylamide salt bridges (230) and the importance of constant geometry in fixed electrode-stirred solution systems (228) have been discuqsed in connection with sulfhydryl titrations. Studies of the reaction of benzoyl disulfide with triphenyphosphine in aqueous methanol have involved the amperometric titration a t a D l I E of thiobenzoic acid n i t h A i g S 0 3(96). Silver in sulfide residues has been determined by dissolution in HS03, precipitation as AgC1, dissolution of this in SH3, and amperonietric titration n i t h sodium diethyldithiocarbamate a t a n R P E of potential +0.4 volt (166). This procedure prevents interference from mercury or bismuth. Silver can be titrated in the presence of nickel and some other ions that can be masked with EDT;I. Sulfenamide-type rubber accelerators have been determined by reduction with SnC12-HC1 and R P E titration in ammoniacal ethanol of the resulting mercaptobenzothiazole with d g s 0 3 (36). The D l I E amperonietric titration of silver with 2-mercapto-
benzoxazole (11) has been applied to a solution that also contains aluminum and manganese (12). These titrations have also been carried out with benzimidazol-2-ylmethanethiol (13). M e t h o d s Involving Mercury. Mercury in HgC1, a n d in mercury ointments h a s been amperometrically titrated with K I a t a platinum microanode ( 186). The rotated mercury wire electrode has been recommended for sulfhydryl titration in bovine-serum albumin with HgC1, or ethyl- or methyl mercury(I1) chloride (135). This electrode is a loop-type RPE that has been coated with mercury. A modified sulfhydryl method that incorporates compensation for the initial current and titration with 0.001M HgC12 has been described (265). d method to prevent loss of sulfhydryl in systems such as flour suspensions has been described by Frater and Hird (69). The successive addition of methylniercury(I1) iodide, reduced glutathione, and then more of the mercury reagent, is involved. Potassium ethylxanthate has been used to titrate milligram quantities of niercury(I1) in ammoniacal tartrate medium (51). The RPE potential is +0.2 volt, when a reversed-L curve is obtained. Mercury and lead can be successively titrated a t a potential of -0.2 volt. Potassium ethylxanthate has been determined by biamperometric titration at mercury electrodes with mercury(I1) acetate or with coulometrically generated mercury(1) ion (124). Mercury(I1) has been titrated with 2-mercaptobenzoxazole a t a stationary platinum electrode ( 1 4 ) . M e t h o d s Involving Lead. N i t r a t e in anhydrous AcOH containing LiOAc has been titrated with P b ( O d c ) p in .icOH a t a D M E a n d a mercury pool anode (143, 144). l’b(T\;03)2 is precipitated. The method has been used for nitrate determination in mineral fertilizers (140). Narunina and Pope1 (163) have used sodium tripolyphosphate to titrate lead in 1JI KSOa. Lead in a buffer of pH 3 to 4 has been titrated with S a r T e 0 3 (60). I’b(0H)S precipitates if the p H is too high, and PbTeOa dissolves below p H 3. The titration of as little as 5 X lO-~JIlead with K2Cr207 by a n ac DME technique has been reported (87). With K2C204as titrant a distinct end point \\a$ obtained with lead concentrations down to 2.5 x 10-4.1f. AC oscillopolarographic iitration with KlCrO, has been applied to the determination of lead in white metal and aluminum alloy2 (121j . Cerium(II1) in 0.5M S H 4 C 1has been determined by boiling ivith solid P b C 2 0 4 and amperometric titration of lead in the filtrate with K2Cr04 (264). An analogous determination of uranyl ion involves treatment with solid Pb2Fe( C S ) 6 . Phosphate in K H 2 P 0 4has been determined by titration with Pb(T\’03)z VOL. 40, NO. 5, APRIL 1968
393 f?
of chromate liberated from solid PbCrO4 (264). The amperometric titration of chromate or dichromate in KNO, with coulometrically generated lead(I1) ion has been reported (304). Similar titrations of oxalate, molybdate, tungstate, and hexacyanoferrate(I1) were also successful. Separation by hydrolysis, dissolution in NaOH, addition of acetate buffer and ethanol, and amperometric titration a t 80' C with Pb(NO& have been used to determine tungsten in high-alloy steel (23). The compounds EtZPbCln and MezPbC12 in aqueous methanolic LiN03 have been titrated with K4Fe(CN)6at a DATE potential of -0.550 volt (211). Treatment with PbC03, removal of dissolved lead by Na2C03,and amperometric titration in KC1 medium at p H 6.5 have been used to determine fluosilicic acid in chromium-plating baths (223). I n the oscillopolarographic D M E titration of lead in N-NH4C1 with EDTA, dissolved oxygen need not be removed (74). The titration of lead with E D T A has been performed coulostatically (274). Lead in 0.01M LiCl in 2-propanolic ethanolamine has been amperometrically titrated with (1,2cyclohexanedinitrilo) tetraacetic acid ( 7 ) . The SCE was made up in acetone. The amperometric titration of lead with 1, 2- c y c 1o h e x anediamine-W,N,N',N'tetraacetic acid (CDTA) and the reverse, have been described (79, 101). At a p H of 5 to 7 and a D M E potential of -0.38 volt, lead can be titrated in the presence of thallium(1). Other reported arnperometric titrations of lead are with thioacetamide (218) and with potassium ethylxanthate (51).
Methods Involving Hexacyanoferrate(I1). Isoniazid has been determined by refluxing with HC1, addition of Y a O H a n d KgFe(CN)s, acidification with H z S 0 4 a n d biamperometric titration of resulting hexacyanoferrate(I1) with ZnS04 (209). Calcium in 0.1JI KC1 liberates cadmium ion when shaken with solid CdC204. Titration with K4Fe(CN)6of cadmium in the filtrate has been used to determine calcium (264). Amperometric titration with K 4 F e ( C x ) 6at a platinum electrode has been used to determine gallium or indium in thin films that also contained arsenic or antimony (268). Several hexacyanoferrate(I1)lead titrations have been reported (211, 264, 304). Amperometric titration has confirmed that Kz(5T0)3[Fe(CN)6]2is formed by the reaction of K4Fe(Cx)6 with VOS04 (225). The precipitate in the amperometric titration of nickel in 0.1X KC1 with 0.004 to 0.05M K4Fe(CN), appears to be essentially xi&,[Fe(CNh14 (87).
Methods Involving Molybdenum and Tungsten Species. T h e amperometric titration of zirconium in 0.1M
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ANALYTICAL CHEMISTRY
KC1-0.01% gelatin with NayMoOa has been carried out a t a D M E potential of -1.7 volt (83). Suprunovich and Usatenko (289) have studied the R P E titration of molybdate with 8-mercaptoquinoline. Anodic oxidation of the titrant causes peaked titration curves. Successive titrations, such as of iron, copper, and molybdenum, were demonstrated and the principle was used to determine iron and molybdenum in chrome-nickel steel. Molybdenum and tungsten in a single sample of high-alloy steel have been determined by hydrolytic separation and subsequent Pb(N03)z titration of tungsten, so that molybdenum in the filtrate can be titrated with 8-mercaptoquinoline (23). Molybdate and tungstate have been amperometrically titrated with coulometrically generated lead ion (304). The amperometric titration of La(NO& with Na2W04,without supporting electrolyte but in the presence of 0.01% gelatin, has been reported (85). Lanthanum polytungstates have been studied by amperometric titration of normal and polytungstates with La(N03)3,and the reverse (239). Results of the titration of c e ( N 0 ~with ) ~ Na2W04 indicate the formation of Cez03.3W03 (84). Very precise end points have been reported in the amperometric titration of NaZUrO4 and polytungstates with TlzSOc and the reverse (236). Thorium in 1.11 KCl-0.01% gelatin has been titrated with Na2W04(86). This titration has been run without supporting electrolyte but in the presence of O . O l ~ o of thymol (238). Accurate results, obtained amperometrically with as little as 0.001JI thorium, are given by conductometric or p H titrimetry only when the reactant concentrations are high.
Methods Involving EDTA or Analogous Reagents. Biamperometric titration with E D T A at a pH of 1.2 t o 1.5 has been used to determine copper in ores and alloys (315). Copper and zinc in the same solution have been titrated at a rotating tantalum electrode (330). After titration of copper a t p H 2, N a O d c is added and zinc is titrated at +1.1 volts. Microgram quantities of calcium have been biamperometrically titrated with 0.001;21E D T A at an applied emf of 1.5 volts (512). The procedure was used to determine calcium in water. The zincate indicator ion method has been used in the D M E amperometric titration of calcium in fertilizers with E D T A (20). Biamperometric titrations of calcium, strontium, barium, and magnesium with E D T A at platinum (311, 314, 316) or graphite (311, 316) electrodes have been studied. Calcium in limestone has been determined by the method (311, 316). Monnier (177) has described the determination of microgram quantities of calcium and
magnesium. The successive titration of these two elements in blood serum and urine has been reported (178). Calcium is titrated with 1,2-bis-(2aminoeth0xy)ethane - N,N,N',N'-tetraacetic acid, then E D T A is used for magnesium. Several papers have described the titration of zinc, cadmium (7, 74, 2741, lead (7, 79, 74, 101, 274), or mercury (99, 100), with E D T A or related compounds. Biamperometric titration with ZnS04 of E D T A released from the aluminum complex has been used to determine alumina in cement (220). The successive titration of bismuth (in 0.2N "03) and cadmium (pH above 4) has been reported (338). Lanthanum in NaC1-KNO3 has been titrated with E D T A a t a D M E of potential -1.5 volts (181). In this and the reverse titration, the current, due to reduction of nitrate, is controlled by the lanthanum concentration. Gallium in a CC13COOH-NH3 buffer (pH 2.1) has been biamperometrically titrated with EDTA, nitrilotriacetic acid (YT.4) and CDTA to form 1 : 1 complexes (317 ) . Triethylenetetramine- A',K,Ai', A; 'IN" ', N"'-hexaacetic acid (TTHA) formed successively 1 :2 and 1: 1 complexes. Vydra and Vorlicek (320) have reported the high selectivity of the biamperometric titration of indium with E D T A a t a p H of 1 to 1.5. They applied the method to determine indium in alloys with antimony and zinc or cadmium. The same workers (318 ) have explored the analysis of gallium-indium mixtures by titrating both metals with E D T A and gallium only with triethylenetriaminehexaacetic acid. Addition of E D T A and back titration of the excess with thallium(II1) has been used to determine zirconium (130). The direct titration of zirconium with EDTA, carried out a t a wax-impregnated graphite anode, has been used to determine zirconium in organic compounds that also contain sulfur (295). Sulfate produced during decomposition of organic material was determined by addition and E D T A back titration of barium ion. The effect of thorium on the reduction of nitrate has been used to carry out the E D T A titration of thorium at a D M E (181). Another method of titrating thorium with E D T A involves a rotating tantalum anode (333). A mean error of *O.3yohas been reported in the biamperometric titration of decigram quantities of thorium with E D T A (319). Only 1 : 1 complexes were formed in the titration of thorium with EDTA, NTA, CDTA, or T T H A (317). Amperometric titration with E D T A has been used to study complexing in the vanadium(1V)-EDTA system [300) and to determine vanadium(II1) in the presence of vanadium(1V) (299). Optimum conditions have been worked out for the biamperometric titration of
bismuth with E D T A (321). This selective and accurate method has been applied to bismuth determination in JVood’s metal. Chiacchierini (40) has studied the reaction between chromiuni(II1) and various complexons. Best results were obtained with CDTA. Other reported titrations with E D T A or related compounds involve uranium (317 ), manganese (274), and iron (323, 317). Methods Involving Other Organic Compounds. Calcium in food extracts has been amperometrically titrated with oxalate at a rotating platinum anode (47). Titration at a D l l E with tartaric acid has been used to determine arsenic(II1) in solutions made from natural and industrial products (54). Polarographic examination of the complexes of germanium with polyphenols such as pyrogallol and gallic acid has shown t h a t germanium can be titrated with such compounds (298). Pyrocatechol ha5 been used to titrate niobium in the presence of tungsten (502). The reaction of copper(I1) and iron(II1) with triphenylmethane dyes has been studied amperometrically 138). T h e reactions of -1lizarin S with beryllium, magnesium and other cations (39) and of humic acid extracts with copper (11) (57) have been studied by amperometric titration. Sickel in plating baths has been titrated with diniethylglyoxime (162). A wax-impregnated graphite electrode was uqed in the titration of copper(I1) with salicylaldoxime (1,50). Resacetophenone has been used to titrate copper (11) in aqueous ethanolic medium a t a D l I E (226). Titration a t a graphite anode with S-benzoylphenylhydroxylamine ha< been w e d to determine gallium in gallium arsenide or phosphide (77). Zirconium in 2.11 H2SOi-0.025M H202has been titrated with cupferron (250). The zirconium-catalyzed H202 reduction current was measured at f0.4 volt vs. a Hg12 reference electrode. d C techniques have been used to titrate copper (26, a?) zinc (26, 27, 88), manganese (88),and some other metals with 8-quinolinol. This titrant has also been used for l1ejSnCl2 and Et2SnCI2 (211). The D l I E titration of 0.023 to 0 . 3 4 5 C d ( S 0 3 ) ~with sodium quinaldinate has been reported (189). A new amperometric titrant for zirconium, di- N a - 2 - (3- methyl - 5 - oxo- 1-phenyl-2pyrazolin-4-ylazo) -6,8- naphthalenedisulfonate, has been announced (214). Vengerova (510) has described the DAIE amperometric titration of codeine and morphine in 0 . 2 5 S HC1 with phosphotungstic acid. Barbiturate derivatives have been titrated with .4gS03 (183). Geyer and Bormann (80) have used a platinum cathode and a gold-plated anode in the amperonietric titration of potassium with NaBPh4. Optimum
conditions for the D l I E titration of copper(1) with NaBPhl have been established (91). Silver and thallium interfere, but most common alloying elements d o not. Copper(I1) can be titrated with either S a B P h 4 or ascorbic acid in the presence of excess of ascorbic acid or of Na13Ph4, respectively (91). Tetraphenylborate has been biamperometrically titrated at silver-plated electrodes with coulometrically-generated silver ion (42). Addition of Ka13Ph4 and dead-stop titration of the excess with T1?;O3 has been used to determine potassium in cement (221). -4similar back titration, a t a D M E , has been used to determine Et3PbCl (211). Aniline and other amines, drugs such as chloropromazine (167), and alkaloids such as strychnine (Q5, 157) have been directly titrated in acetate medium with S a B P h 4 . At a potential of +0.18 volt, the D l I E is the anode and is depolarized by excess of titrant. Tetrafluoroborate in well-stirred alkaline solution has been determined by addition of CH2C1, and D l I E amperometric titration with Ph+lsCl (10). The water-insoluble complex passes into the CH2C12and a reversed-r, titration curve is obtained. Thorium in NaCl-KSO3 medium has been amperometrically titrated with benzenephosphonic acid (181). A similar titration of lanthanum gave erratic results. Extraction with trioctylamine and subsequent titration with *\rsenazo(II1) has been used to determine uranium(1V) in solutions also containing uranium(T’1) and iron (297). 11illigram amount3 of thioacetamide have been determined by the D l I E aniperometric titration of copper(1) produced by mixing copper(I1) and (NH2OH)2*H2S04 (219). Thioacetamide has been used to titrate copper and lead in the presence of zinc (218). The amperometric titration of copper and palladium with 2-niercaptobenzoxazole (11 , 12) or with benzimidazol-2-ylmethanethiol (13)has been described. Titrations that involve silver and thiobenzoic acid (96), sodium diethyldithiocarbamate (156),2-mercaptobenzoxazole, (11, 12), benzimidazol-2-ylmethanethiol (13), 2-mercaptobenzothiazole (36),and sulfhydryl groups in biologically-important and other substances (127, 136, 167, 186, 228, 230, 269) have been reported. -4mperometric titrations involving potassium ethylxanthate have been used to study the reaction of this compound with cadmium ion (325),to determine this compound with niercury(1) or mercury(I1) ( l a d ) , and in the successive determination of mercury(I1) and lead (51). l l e r c u r y compounds have continued to find use as titrants for sulfhydryl groups (69, 136, 266) and have been titrated with 2-mercaptobenzoxazole (14). The amperometric titration of gold
(111) with thiourea appears to involve both reduction to gold(1) and combination to form [AuSCX2H4]+ (ZO4). Gold in ores, crude copper, etc., has been determined by this method. Sodium diethyldithiocarbamate has been used to titrate indium at a D l I E potential of -0.8 volt (275) and tellurium (IV), or selenium(1V) plus tellurium (IV), at a n RI’E potential of +0.7 to +0.8 volt, or +0.8 to f0.9 volt, respectively (307). Lead is added as indicator ion when selenium is involved. Tellurium and selenium plus tellurium have also been titrated with sodium hexyland cyclopentylthiocarbamates, which are more stable in acid solution than the diethyl compound (503). Reduction to vanadium(1V) has been shown to occur when vanadium(V) in 0.1s H2SO4and similarly acid media is titrated with 8-mercaptoquinoline (206). Precipitation without reduction occurs in phosphate buffers of pH 5.4 and 6.8. Titration with 8-niercaptoquinoline has been used to determine vanadium in ferrovanadium (206, 208) and molybdenum in steels (23, 207, 289). Miscellaneous Titrations. N i t r a t e in anhydrous HOAc has been titrated at amalgamated copper electrodes with 13a(OAc)2 in H0.k (141). The D l I E amperometric titrations in HO-ic, with C d ( S 0 3 ) 2 ,of compounds such as KCl, S H 4 C l (25, f 4 2 ) , NaI3r, SH4SCN ( 142), and carboxylic acid chlorides (25) have been reported. The reaction between thallium(1) and alkali polyvanadate has been studied amperometrically ( 175). In 50% aqueous ethanol, well-defined breaks at the T120:V205 mole ratio of 1 : 2 . 5 were obtained. Hydroquinone or p-aminophenol has been used as electrometric indicator in the titration of barium, zinc, etc., with S a 2 C 0 3 and of copper (11), nickel, etc., with K C T (234). Copper plus zinc in solutions made from brass has been determined by addition of diantipyrylmethane arid anodic R P E amperometric titration with KSCS (168). Zinc only was determined in another aliquot that had been boiled with aluminum before addition of diantipyrylmethane (or diantipyrylmethylmethane) and titration. Electroplating solutions have been amperometrically analyzed by methods baqed on the precipitation of copper, zinc, and nickel thiocyanates from pyridine-containing solutions (1627). A study of the complexes of zinc, cobalt, and nickel with 2,3- and 4-picoline has shown that a picoline-containing medium is suited to the amperometric titration of these metals (201). The response of the zirconium-catalyzed H202 reduction current was found to be sluggish in the D N E titration of zirconium with phosphate (251). Phosphate has been titrated with B i ( S 0 3 ) 3 a t a graphite electrode (160) and with VOL. 40, NO. 5 , APRIL 1968
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395
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coulometrically generated bismuth ion at a D M E (305). Sodium tripolyphosphate has been used to titrate cadmium and lead in KNOa, or iron(II), cobalt, and nickel in HK03-KC1 medium (163). Amperometric studies on thorium polyvanadates have shown that Th(K03)4can be rapidly and accurately titrated with sodium orthovanadate at a DJIE potential of -1.5 volts (240). No supporting electrolyte was used in this or the reverse titration. Similar studies on uranyl (174) and nickel (241) polyvanadates have indicated that amperometric titrations of uranyl ion or nickel with sodium orthovanadate are precise and accurate. The composition of the complex 3CrC13.K2H4has been studied amperometrically (222). Thallium (I) has been titrated with K2Cr207 in the presence of lead by masking the latter with CDTA (79). The optimum p H in the D M E titration of copper(I1) with NazTe03has been shown to be 4 to 5.2 (50). Iron(II1) has been used as indicator ion in amperometric titrations with K a F of aluminum in chromites (18) and in titanium-containing nickel alloys (115), and of fluoride with zirconium (196). Titration with ZrOCl? has been used to determine fluoride in etching solutions (195) and in slags and fluxes (194). Silver and silver plus palladium (273) and bismuth (31) have been titrated with K I . The titration of bismuth is carried out in the presence of e-caprolactam, when [(C6H11x0)2H]Bi14 is precipitated. OXIDATION-REDUCTION REACTIONS
M e t h o d s Involving Iron. Singh and Varma (261) have described the successive biamperometric titration of cerium(1V) and vanadium(V) with hlohr’s salt. The successive titrations of Mohr’s salt and oxalic acid with Ce(S04)2or KhhO4, and of llohr’s salt and YOSO,, with KMn04, have been reported (254). The titration curve of iron(I1) with cerium(1V) has been automatically recorded (199). =Ifter a study of platinum anode-dissimilar metal cathode systems, Filenko (65) has recommended a tungsten cathode for the titration of permanganate with llohr’s salt. This or a silver cathode was found best for the titration of vanadate or dichromate. Vanadium in steel (63, 125) and in high-temperature alloys and slags (283) has been biamperometrically titrated with Mohr’s salt. The successive titration of FeS04 and CoS04 with NH4V03 (258) or with K2Cr2O7 (260) has been described. Royon (232) has studied the electrode reaction kinetics in the biamperometric titration of iron(I1) with K2Cr2O7. Amperometric titration with coulometrically-generated iron( 11) has been applied to the determination of submicrogram amounts of chromium(V1) 396 R
ANALYTICAL CHEMISTRY
(43), and of the purities or concentrations of solutions of K2Cr207and K l l n O , (328). Biamperometric titration with Mohr’s salt has been used to determine chromium (62) or chromium and vanadium (61) in alloy steels. A simplified amperometric determination of manganese, chromium, and vanadium in minerals and ores has been reported (190). This involves the iron(I1) titration of one aliquot for all three metals, and of a second aliquot for chromium and vanadium only. The second aliquot is again titrated after oxidation of vanadium with KMnO,. Reduction in NaOH-N(C2H40H)3 at 50’ to 60’ C with Mohr’s salt and back titration with K2Cr207has been used to determine 1-phenylazo-2-naphthol and other azo compounds (66). Amperometric titration, a t a platinum anode or a platinum-tungsten electrode pair, with electrogenerated iron(I1) has been used to determine molybdenum in steels and alloys (4). Silica in SiOs and granite has been determined by carbonate fusion, conversion to a-12molybdosilicic acid, and biamperometric titration with iron(I1) (SO). The R P E titration of iron(I1) with KMnO4 has been run without applied emf by use of a mercury-Hg2SOa reference electrode (100). Kostromin and Kruglov (139) have used biamperometric titration of iron(I1) with electrogenerated bromine to determine iron impurity in selenium. Anthraquinone and 13 of its derivatives have been biamperometrically titrated in NaOH-S(C2H,OH)3 with hlohr’s salt (56). Biamperometric indication has been used in the coulometric titrations of microgram quantities of titanium, either alone or in the presence of excess vanadium, with iron(II1) (267),and of iron(111) with titanium (111) generated a t a copper amalgam cathode (268). An amperometric study of the iron(II1)unithiol reaction has shown that the precipitated Fe(OH), is reduced to Fe(OH)*, which dissolves in excess unithiol (200). Current-strength equations for biamperometric titrations and stationary electrodes have been checked by titrating hexacyanoferrate(I1) with KAfnO4 (60). The successive titrations of K4Fe(CN)6 and oxalic acid with Ce(SO& or KLhO4, and of K 4 F e ( C S ) and ~ Voso4 with K M n 0 4 have been reported (254). Submillimolar concentrations of K3Fe(CN)6 in KSCN-HC104 have been titrated with Hg2(C104)2a t an RPE potential of zero (282). Results were unsatisfactory in KaOH-KI. Hexacyanoferrate(“, either alone or in the presence of iron(”, has been biamperometrically titrated with electrogenerated molybdenum(V) (59). Molybdenum in ores has been determined by N2H4 reduction to molybdenum(V) and biamperometric titration with K3Fe(CN)e (302). 11-
though the RPE titration of arsenic(II1) with K3Fe(C?;)6 was satisfactory the titration of antimony(II1) was found to be imprecise (332). KAIn04 has lieen determined in alkaline medium by addition of K 4 F e ( C x ) 6and Os04-catalyzed R P E titration of the resulting hexacyanoferrate(II1) with Sa;is02 (49). Nonferrous Methods Involving Cerium, Titanium, Vanadium, Chromium, and Manganese. Best results in t h e R P E titration of cerium(II1) with K M n 0 4 were obtained in 3 5 KzC03 a t a potential of f 0 . 2 volt ($31). Thallium(1) has been biamperometrically titrated with Ce(S04)? at room temperature by use of LlnS04 or IC1 as catalyst (255). The R P E titration of cerium(I1’) in lLV H N 0 3 with NaKOz has been hastened by Os04 catalysis 1337). Cerium(1V) has been titrated redoxokinetically with vanadium(I1) (145) and biamperometrically with electrogenerated molybdenum(V) (59). iiddition of CC14 and biamperometric titration with cerium(1V) has been used to determine iodide in the presence of a 10-fold excess of bromide (271). Oxidation by Ce(C10a)4and R P E back titration of the excess with Na2C204has been used to determine aliphatic alcohols (171). Cerium(1V) titrations of a-hydroxy and a-oxo-carboxylic acids in anhydrous HO=lc (%), and solids-not-fat in milk (624) have been run biamperometrically. So has the titration of Ce(S04)2 with methylene blue (217). The successive titration of cerium(1V) and either vanadium(V) or molybdenum (VI) with ascorbic acid has been run by changing the p H after the cerium end point (266). R P E titration of vanadium alone, then of cerium plus vanadium in the same solution, with 8-mercaptoquinoline has been used to determine these metals in iron and steel (24). Biamperometric titration with Ce(S04)2 has been used to determine drugs such as chloropromazine (161, nozinan (15, 182) promethazine methowlfate ( I ? ) , and butaperazine diphosphate (184). Gold(II1) in the presence of platinum and palladium has been determined by a method that involves the amperometric titration of pyramidone in KBr with Ce(SO& (159). Biamperometric indication has been used in the coulometric titration of molybdenum(V1) (21, 327) and of iridium(1V) (277) with titanium(II1). The titanium(II1) titration of rhenium (VII) a t a graphite electrode or RPE has been applied to alloys of rhenium with titanium, molybdenum, or tungsten (75). Titanium in the presence of nickel, copper, etc., has been determined by the titanium(II1)-methylene blue reaction (147). Automatic titration of uranium(V1) with chromium(I1) at a vibrating D M E has been used to evaluate rate constants for the disproportionation of uranium
(V) (35). Two breaks have been found on the chromium(I1) titration curves of mixtures of chromium(VI), molybdenum(VI), or iron(II1) with rhenium (VII) ( 7 6 ) . Rhenium alloys were analyzed by this method. The 3InSO4catalyzed K2Cr207biamperometric titration of thallium(1) in 10X HzS04 has been reported (253). The D M E titration of thallium(1) with K2Cr04has been run in the presence of lead by masking this with CDT=I (101). Hydroquinone ha3 been biamperonietrically titrated v i t h Ii2Cr207a t 40’ t o 60’ C (176). The R P E titration of cerium(II1) (331) and the biamperometric titration of thallium(1) (128) with KMnOc have been described. Other reported titrations with K31n04 include those of H 2 0 L (112, l69),chroniium(II1) (170), manganese(I1) (13, 111, 110), and dihydrallazine (220). The last titration is run in HC1-KUr medium. Permanganate has been titrated with l;aXO2 (335, 33?), VS04 (145),H202(335),and electrogeneiated molybdenuni(V) (59). Several methods have been evolved for the aniperometric analysib of mixtures of dichromate with permanganate (335),or with permanganate and cerium(IT*) (384). For example cerium(1V) was masked with S a F and permanganate waq titrated with S a S O , . Cerium(IV), released by increaqing the acidity, was then titrated with S a S O z . Finally, excess S a S 0 2 was destroyed by urea and dichromate naq titrated with H202. 13iamperonietric (128) and redoxokinetic (146) indication in titrations involving manganese(II1) have been examined. M e t h o d s Involving Chlorine or Bromine. hrsenic(II1) (42), carbutamide (119), and after alkaline hydrolysi‘, caffeine (118),have been coulometrically titrated with chlorine to a biamperometric end point. Thallium(1) (128) and cobalt, in the presence of E D T A to lower the redox potential (259), have been biamperonietrically titrated with chloramine T. Bromine chloride has been used as a potentiometric and R P E amperometric titrant for SnC12, As203, potassium antimonyl tartrate, NazS03, and ascorbic acid (136). Thalliuni(1) has been determined without interference from lead, bismuth, iron, etc., by oxidation with K l l n O c to thallium(II1) and amperometric titration with Kl3r (151). Biamperometric indication is commonly used in coulometric bromine titrations. The following are 5ome recent examples. Microgram amounts of thallium in blood and urine have been determined by HS03HzS04 digestion, extraction with and reinoval of ether, and reduction with S a 2 S 0 3 before titration (45). Tagliavini (290) has titrated hexamethylditin and analogous compounds, but obtained uniatiifactoi y result5 with hexaphenylditin. The action of a continuous re-
cording titrator has been illustrated by the determination of X2H4 in a gas stream (229). Generation of excess bromine, addition of sample, and observation of the resulting current decrease, have been used to determine nanogram quantities of arsenic(II1) (41). The arsenic(II1)-bromine reaction has been used to study the automatic recording of biamperometric titrations (42) and t o determine drugs such as quinine sulfate or sulfaguanidine (37). The direct titration of these drugs gave a premature, unstable, end point. As soon as this was observed, a known amount of arsenic(II1) was added and titration was continued to a stable end point. The rapid titration of Sals03 and of ethyl mercaptan has been described 1213). Christian (42) has observed t h a t the biamperometric titration curve of iodide with bromine has a single maximum a t lo^ iodide concentrations, but that two maxima appear when the iodine concentration is increased. Coulometric titration with bromine to a biamperometric end point has been applied to various organic compounds. Microgram amounts of beryllium in gallium have been determined by formation of the beryllium-acetylacetone complex, extraction into benzene or CC14, evaporation, acidification, and titration (138). Titration with bromine has been used to determine phenol for control of its alkylation by a-olefins in the presence of benzenesulfonic acid (148). Podolenko (212) has reported a n error of =t5yoin the automatic titration of microgram amounts of phenol, resorcinol, etc. Schonberger (243) has described the potentiometric titration of phenol in the presence of a n equal amount of acetone. H e found amperometric or biamperometric indication to be unsatisfactory. Aluminum impurity in antimony, K2Cr04, KaOAc (IS?’), and selenium (139) has been determined by precipitation with 8-quinolinol and subsequent titration of this compound. The +0.47, error in the titration of centigram amounts of carbutamide with electrogenerated bromine is two thirds of that in the analogous titration with chlorine (119). Biamperonietric indication has also been used in kinetic studies of the reaction of electrogenerated bromine with ethyl acetoacetate (52) and diphenyl sulfide (103). Titration with bromine in glacial HOXc a t a fixed platinum electrode has been applied to monomers such as vinyl acetate, either alone or in polymeric products (89). IlPE indication has been used in a kinetic study of the bromination of 8-quinolinol and certain of its 4- and 5-substitution products (198). A vibrating electrode was used in a kinetic study of bromine with organic sulfides (102). Biamperometric titration with K B r 0 3 has been used to determine thallium(1)
in mixtures with large amounts of copper, iron, etc. (128, 129), and in the presence of antimony (129). K B r 0 3 has also been used to titrate antimony in alloys with gallium or indium (288), N2H4 ( 1 1 4 , chlorpromazine (22), and unsaturated organosilicon compounds (161). The direct coulometric hypobromite titration of Kjeldahl digests to a biamperometric end point has been applied to the routine determination of S H 3 obtained from 10-111 samples of human serum (44). X study of the RPE titration of arsenite with hypobromite has shown that the alkaline titrant contains rapidly-reacting BrO- and slowly-reacting B r 0 2 - (309). Errors less than 0.2% have been reported in the biamperometric titration of from 1 to over 100 peq of Hz02with electrogenerated hypobromite (68). Compounds such as 4 S z o 3 , SnC12, ascorbic acid, and antipyrine have been titrated a t a n RPE with iodine bromide (188). M e t h o d s Involving Iodine. The biamperometric titration of selenium (IV) with K I (3) or with electrogenerated iodide ion ( I ) has been described. Selenium has been titrated in the presence of a 10- to 50-fold excess of tellurium ( 2 ) . Biamperonietric titration of iodide in dimethylformamide with electrolytically-generated iodine gave a n end point corresponding to the formation of triiodide ion (263). Micromolar concentrations of iodine in H2S04-KI have been titrated at a n R P E with Hg2(C104)2 (281). Coulometric titration with iodine to a biamperometric end point has been used to standardize NaAsOz solutions (328). Addition of excess arsenic(II1) and coulometric back titration with iodine has been used for the precise determination of KaOCl (146). The lower precision in Ca( 0 C l ) ~determination was attributed to electrode fouling and sample nonhomogeneity. Vanadium(1V) in a n ammoniacal medium of p H 9 to 10 has been biamperometrically titrated with iodine (262). The titration of N?H4 with iodine has been used to illustrate the magnitude of the end point currentjump with a n irreversible titrand system (114). The coulometric titration of Na2S with iodine has been described (613). Sulfite in solutions stabilized by a small amount of E D T A (322), and in spent pulp liquors (323),has been determined by titration with iodine. Kovak (191) has developed a continuous analyzer for 1 ppm or less of SOz in gases. A slow stream of dilute H 2 S 0 4that is saturated with iodine flows through the cell and the gas sample enters near the platinum anode. Iodide produced by the SO2 gives a current that is proportional to the SO?concentration. A platinum in K2Cr20i reference electrode permits VOL. 40, NO. 5 , APRIL 1968
e
397 R
operation without a n external emf source. Two streams of 0.5 to 5% X a I circulate in the combined 0 3 and SOz in air analyzer devised by Schulze (246). One air stream is metered through the SOn-removingCr03-H3P04 scrubber into the first N a I stream, when the biamperometric current due to liberated iodine measures 03. A second air stream passes through the 03-removing FeS04. 7 H 2 0 scrubber into the second N a I stream, into which iodine is electrolytically introduced. d decrease in the biamperometric current measures SO2. Iodine removal by a nylon fiber absorber allows the same X a I solution to be circulated repeatedly. Biamperometric indication has been used in the coulometric titration with iodine of hexaethylditin (290), arsenic (111), and thiosulfate (42). Probable errors in the biamperometric titration with K I 0 3 of submillimolar concentrations of mercury(I), thallium(I), antimony(III), and thiocyanate have been evaluated (70). Other KIOz titrations have involved thallium(1) in mixtures with other metals (128, 129), molybdenum(]-) (69), and the determination of SOzin wines (205). Dissolved oxygen in water has been automatically determined by a sequence that involves iodine liberation, addition of Xa2S203, and back titration with K I 0 3 (292). Interest in nontitrimetric iodine-producing reactions has continued (233). hlagno and Fiorani (160) have used RPE and biamperometric techniques to study the kinetics of the iodateiodide reaction. Further studies on the determination of microgram amounts of zirconium (252), molybdenum (29, 248, 249), and tungsten (29), by their catalytic effects upon the H20n-iodide reaction have been described. Automatic zero compensation and calibration have been devised for glucose determination, based upon the the enzymatic production of H202and its effect upon the molybdenumW1)(203). Microgram iodide reaction amounts of germanium (168) and of sulfide (172) have been determined by their catalytic effects upon the molybdenum (VI)-iodide and the iodine-azide reactions, respectively. Water determination by the Karl Fischer method has continued to be an important application of biamperometric titrimetry. Procedures have been described for water determination in organic hydrates (46), alkaloids and their salts (216), organic iiquids (I%), gaseous hydrocarbons (131), acetaldehyde (179), silicone materials (270), freons, furan, etc., (202), fertilizers (34, 2 4 4 , gelatin (go), and molasses (242). Several general papers have also appeared (5,93, 286, 326, 341). Easily-hydrolyzable acid chlorides have been determined by addition of water and back-titration with Fischer reagent (72). 398
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ANALYTICAL CHEMISTRY
Other Reactions. Optimum conditions have been found for t h e amperometric titration with electrogenerated copper(1) of iridium(1V) in t h e presence of a 10-fold excess of osmium, rhodium, and palladium (276). Micronormal concentrations of copper (11) in KSCN-KI-HC104 medium have been titrated with Hg,(C104)2 at a n RPE of zero potential (280). The three-electrode D l I E titration with thallium(1) of oxygen in 0.1JI KCIOl in dimethylsulfoxide solution has been reported (107). The basis of this interesting titration is that addition of thalliumiI) to the oxygen solution produces a new wave a t potentials less negative than required for thallium(1) reduction. Persulfate has been coulometrically titrated to a biamperometric end point with molybdenum(V) (59). Sulfamic acid, H202(336), and S2H4 (339) in dilute have been titrated with S a N 0 2 a t a n R P E potential of 1.0 volt. With H202, equilibration requires only about 30 seconds. Several biamperometric titrations of organic compounds with S a S O z have been reported. Ericson and Schill(56) found no complications in the titration of o-aminophenols and alkoxy derivatives of aminophenols. Although p-aminophenol. and maminophenols gave unstable currents before and after the end point, respectively, r e a l t s were satisfactory. Ailminonaphthols could not be titrated accurately, possibly owing to oxidation. The rapid titration of sodium cyclamate in soft drinks has been described (2$7). Average errors ranging from -0.34 to +0.23y0 have been reported in the titration of p-aminobenzoic acid, procaine, sulfaguanidine, sulfamethazine, and sulfathiazole (154). The degree of hydrolysis of procaine solutions has been determined by extracting the procaine into CHC13 and subsequently titrating it. p-Aminobenzoic acid in the aqueous layer is titrated separately (324). Titration in acidified KBr has been used to determine ethacridine lactate (216) and sodium p-aminosalicylate after its separation from isoniazid (210). Matrka and Marhold (166) found that biamperometric indication could not be w e d in the titration of metal. Singh and Bhatnagar have used biamperometric titration with ascorbic acid to analyze various binary mixtures. Thallium(II1) in mixtures with silver is titrated in 0.1 to 1N H2S04,then silver is titrated after raising the p H to 6.5 to 7 (255). Gold(II1) and mercury(I1) in 0.1.lI &So4 are successively titrated without change of medium (257). Mixtures of cerium(1V) and vanadium (V) or molybdenum(V1) are analyzed by lorvering the acidity after the titration of cerium (256). Amperometric titration in 0.1.V XaC1 Kith hydroquinone has been used for the
+
rapid determination of iridium(1V) in the presence of other platinum metals (149). X study of the R P E titration of gold(II1) with thiourea indicates that [Au(SCN*H4)2]+is formed (204). The procedure was used to determine gold in ore and metal concentrates. As little as 1 pg of thallium(II1) in 40 ml has been amperometrically titrated with thiourea (306). Potentiometric titration is also possible, but the lower limit is 10 pg. Titration of slightly acid gold(II1) with thiopiperidone gives .iu2S2 (29293). Gold can be determined in the presence of copper(I1), seleniumiIV), and tellurium (IV) if copper is masked with EDTA. The titration of vanadium(V) (208) and molybdenumiV1) (207) with 8-mercaptoquinoline has been studied and applied to the analysis of ferrous alloys. The R P E titration of methylene blue has been used to determine tin(I1) and titanium(II1) in the presence of copper, iron, etc. (147). This lvork was carried out with the partial support of the U. S. Atomic Energy Commission (Contract AT(30-1)-1977). LITERATURE CITED
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(21 Ibid.. 96 11966): CA 66. 8082w (1967). (3) Agasyan, L. B., Nikolaeva, E. R., Agasyan, P. K., Zh. Anal. Khim. 21, 1470 (1966). ( 4 ) Agayyan, P. K., Tarenova, K. Kh., Nikolaeva, E. It., Katlna, It. AI., Zavod. Lab. 33, ,547 (1967). (3) Akiyama, T., Kyoto Yakka Daigaku Gakuho N o . 12, 1 (1964); C.4 63, 17104f (196.5). (6) Alexander, W. A., Barclay, D. J., J . Electroanal. Chem. 12, 35 (1966). ( 7 ) .4rthur, P., Hunt, B. It., ANAL.CHEK 39,Y.i (1967). (8) Bagbanlv, I. L., Alekperov, A. G., llamedkuheva, M. hl., Bagbanly, S. I., Dokl. Akad. S a u k Aterb. SSR 21, 1,5 (196.5); CA 64,18401h (1966). ( 9 ) Banerjea, D., Das Gupta, T. P., Indzan J . Chem. 4,91 (1966). (10) Behrends, K., 2 . -4nal. Chem. 216, 13 (1966). (11) Bera, B. C., Chakrabartty, AI. M., Anal. Chim. Acta 33,564 (1963). (12) Bera, B. C., Chakrabartty, 11. AI., Chem. Ind. (London)1966,458, (13) Bera, B. C., Chakrabartty, hl. If., Talanta 13, 1186 (1966). (14) Bera, B. C., Chakrabartty, 11. ?f., Bag, S. P., and Mallik, K. L., Ibzd., 13,328 (1966). (15) Beral, €I., Murea, L., Madgearu, M.,Cuciureanu, E., Acta Pharm. Jugoslav. 15, 77 (196.5). (16) Beral,. H., Murea, L., Madgearu, XI., Cuciureanu, E., Wermescher, B., Pharm. Zentralhalle 104, 231 (196I., 2. Anal. Chem. 217.239 11966). (34) Caro, J. H'., J.' Assoc. Of. Agr. Chemists 47,626 (1964). (35) Cam, P. W., Neites, L., J . Electroanal. Chem. 12,373 (1966). (36) Chakravarti, S., Sircar. A. K., Trans. Inst. Rubber Znd. '41, T221 (1965). (37'1 Charles. R. L.. Knevel. A. AI.. J . Pharm. Sei. 54,16?8( l965).' (38) Chernova, R. K., Materialy K Konf. Molodykh *Yauchn.' Rabotn. -Saratovsk. Med. Inst. Sb.. Saratov 1964. 37: CA 65, 9708d (1966). (39) Chernova. R. K.. Tr. Molodukh ' dchenykh, S&-atovsk~Uni~., Vpy. Khim., Saratov 1965, 173; C A 65 4644f (1966). (40) Chiacchierini, E., -4nn. Chim. (Rome) 56,1405 (1966). ' (41) Christian. G. D.. Jficrochem. J . \
-
(42j Christian, G. D., J . Electroanal. Chem. 11.94 (1966). (43) Chris{ian, G. D.,Feldman, F. J., Anal. Chzm. Acta 34, 115 (1966). (44) Christian, G. D., Knoblock, E. C., Purdv, W. C.. Clzn. Chem. 11. 413 (196,s): (45) Christian, G. D., Purdy, W. C., Am. J . Clin. Path., 46, 185 (1966). (46) Corlibs, J. hI., Buckles, 11. F., Microchem. J. 10,218 (1966). (47) Danilova, E. N., Shemyakin, F. AI., Izv. Vysshikh Uchebn. Zavedenii, Pishchevaya. Tekhnol. 1965, 173; CA 63. l5539h (1965). (48) 'Den Boef. G., Chem. Weekbl. 63 , 261 (1967). (49) Deshmukh, G. S., Kane, Y. D.1 Indian J . Chem. 3,570 (1965). (50) Deshmukh, G. S., Rao, V. S. S. Zbid., 5,37 (19671. (51) D'eshmukh. (2. S.. Saraswathi. K.. Ibid., 3,489 (1965). ' ( 5 2 ) Dubois, J. E., Alcais, P., Barbier, G., J . Electroanal. Chem. 8, 359 (1964). (53) Durat, R. A, J . Chem. Educ. 43, 437 (1966). (54) Elenkova, N., Todorova, G., Compt. Rend. Acad. Bulgare Sci. 18, 429 (1965). (S) Eremias, B., Prikryl, Z., Zyka, J., Collect. Czech. Chem. Commun. 32, 2478 (1967). (56) Ericson, C., Schill, G., Acta Pharm. Suecica 3,403 (1966). I
,
( 5 7 ) Eschena, T., Ann. Fac. Agrar. Univ. Studi Perugiu 19, 63 (1964); CA 65, 4584d (1966). (58) Feldman, F. J., Bosshart, R. E., ANAL.CHEM.38,1400 (1966). (59) Feldman, F. J., Christian, G. D., J . Electroanal. Chem. 12, 199 (1966). (60) Filenko, A. I., Khim. i Khim. Tekhnol., Alma-Ala, Sh. 2, 114 (1964); CA 64. 1333a (1966). (61) File'nko, A.' I., I h . Vysshikh Uchebn. Zavedenii, Khim. i Khim. Tekhnol. 8, 397 (1965); CA 63, 17129f (196j). (62) Filenko, A. I., Zavodsk. Lab. 32, 287 (1966). (63) Filenko. A. I.. Ukr. Khim. Zh. 33. 632(1967): (64) Filenko, A. I., Zh. Anal. Khim. 21, 1495 (1966). (65) Zbid., 22, 161 (1967). (66) Fiorani, M.,Ric. Sci. 36, 588 (1966). (67) Fleury, S., Pharm. Biol. 5, 2.5 (1967). (68) Fol'b, I. L., Lab. Delo 1965, 507. (69) Frater, R., Hird, F. J. R., Biochem. J . 96,895 (1965). ( 7 0 ) Freddi, R., Bombi, G. G., Fiorani, M., Z. Anal. Chem. 222,369 (1966). (71) Freese, F., Chem. Weekbl. 61, 553 (1965). (72) Frehden, O., Petroianu, S., Rev. Chim. (Bucharest) 16,223 (1965). ( 7 3 ) Fujinaga, T., Izutsu, K., Takaoka, K., Rev. Polarog. (Kyoto)13,42 (1965). (74) Gabovich, A. M., Tr. Kishinev. Sel.-Khoz. Inst. 43, 125 (1966); CA 66, 121719n(1967\. (75) Gallai; Z. A., Rubinskaya, T. Ya., Zh. Analit. Khim. 21,961 (1966). (76) Gallai, Z. A., Rubinskaya, T., Ya., Fursova, A. V., Ibid., 21, 584 (1966). ( 7 7 ) Gallai, Z. A., Sheina, N. hi., Alimarin, I. P., Zhid.'20, 1093 (1965). ' (78) Gatto, J. T., Stone, K. G., Talanta 13. .i97 (1966). (79) 'Gaur, J. N., Jain, D. S., Acta Chim. Acad. Sci. Hung. 51,171 (1967). (80) Gever, R., Bormann, H. D., Wiss. Z . T&h. ' Hochsch. Chem. LeunalMerseburg 7, 243 (1965); CA 64, 166199 (1966). (81) Gordienko, V. I., Kovalenko, P. S.,Ivanova, Z. I., Izv. Vysshikh Uchebn. Zavedenii, Khim. i Khim. Tekhnol. 8, 549 (1965); CA 64,42369 (1966). (82) Gross, D. J., Murray, R. W., KirkOthmer Encycl. Chem. Technol., Ind Ed. 7,726 (1965). (83) Gupta, C. AI., 2. Anal. Chem. 204, 181 (1964). (84) Gupta, C. M., Bull. Acad. Pol. Sci., Ser. Sci. Chim. 13,167 (1965). (85) Gupta, C. >I., Bull. Chem. SOC.Japan 38,1401 (1965). (86) Ibid., 39,837 (1966). (87) Gupta, S. L., Sharma, S. K., J . Indian Chem. SOC.42,381 (1965). (88) Gupta, S. L., Sharma, S. K., Jaitly, J. N., Indian J . Chem. 4, 166 (1966). (89) Gurvich, D. B., Balandina, V. A., Ivanyak, A. G., Zavodsk. Lab. 31, 288 (1965) --, (90) Gyore, J., Szilagyi, G., Simon, I., Barkics, hI., Magy. Kem. Folyoirat 72, 7 (1966). (91) Hartley, A. hl., Hehner, A,, Collection Czech. Chem. Commun. 30. 4250 (1965). (92) Helbig, W., Chem. Tech. (Berlin) 18, 344 (1966). (93) Hesse, G., Herb, W., Zbid. 15, 690 (1963). (94) Hilton, C. L., Encycl. Ind. Chem. Anal. 1,634 (1966). (95) Hsu, L., Chou, T., Yao Hsueh Hsueh Pao 12, 798 (1965); CA 65, 3917e (1966). (96) Humphrey, R. E., Renfro, J. C., Talanta 13,1075 (1966). (97) Ikeda, S., hlusha, S., Bunseki Kagaku 15,871 (1966). ~
\ - -
(98) Ikeda, S., Nishida, S., Ibid., 610 (1966). (99) Israel, Y., Vromen, A., Israel J. Chem. 2,273 (1964). (100) Israel, Y., Vromen, A,, J . Electroanal. Chem., 11,262(1966). (101) Jain, D. S., Gaur, J. N., J. Indian Chem. SOC.42,753 (1965). (102) Janata, J., Schmidt, O., Zuman, P., Collection Czech. Chem. Commun. 31,2344 (1966). (103) Janata, J., Zyka, J., Ihid., 30, 1723 (1965). (104) Jantti, O., Suomen Kemistilehti 39.147 11966). (lO5j Jennison,' W., Clark, hl. L., A n alyst 91.598 - ~ 11966). (106) Johnson, E. L., Pool,, K. H., Ha mm, R. E., ANAL.CHEM.3 8 , l 83 (1966). (107) Zbid.,, 39,. 888 (1967). (108) Jovanovic, &I. S.; Babic, R. V. 1 Glasnik Hem. Drustva, Beograd 29, 11 (1964). (109)'Jovahovic, M. S., hlojsilovic, >.I M., Sigulinsky, F. D., Zbid., 443 (1964). (110) Jovanovic, N. S., Petrovic, D. h1.. Ibid.. 445 (1964). (111)' Jovanovic; hI.' S., Petrovic, D. kl., Talanta 13,816 (1966). ( I 12) Jovanovic, 11. S., Sigulinsky, F. D., Glasnik Hem. Drustva., Beoarad 29. " 444 (1964). (113) Jovanovic, Ill. S., Sigulinsky, F. D., Dragojevic, AI., Talanta 13, 1275 (1966). (114) Jovanovic, 11. S., Tijeglic, N., Selmic, I., Vukosavljevic, V., Glasnik Hem. Drustva, Beograd 29, 442 (1964). (115) Jurczak, K., Prace Inst. Mech. Precyzyjnej 12, 59 (1964); CA 67, 17524e (1967). (116) Kabasakalian, P., Yudis, hI. D., Encycl. Znd. Chem. Anal. 1,122 (1966). (117) Ihid., 3, 161 (1966). (118) Kalinowska, Z. E., Acta Polon. Pharm. 2 1,365 ( 1964). ( 19) Kalinowska, Z. E., Korzybski, R., Ibid., 21,473 (1964). ( 20) Kalinowski, K., Farm. Polska 21, 914 (1965). ( 21) Kao, H., Peng, T., Chang, W., Hua Hsueh Hsueh Pao 31, 428 (1965); CA 64,73j6f (1966). ( 22) Kashlinskaya, S. E., Strel'nikova, X. P., Prelovbkaya, Z. Ya., Analiz Blagorod. Met., Moscow 1965, 16; CA 66,913799 (1967). ( 23) Kekedy, L.,jJ"Omagiu Acad. Prof. Raluca Kipan, 1966, 306; Anal. Abstr. 14,2548 (1967). (124) Kekedy, L., hlakkay, F., Studia Univ. Babes-Bolyai, Ser. Chem. 9, 5,; (1964): CA 64.1357e 11966). (125) Zbid.,' 11, 21 (1966); ' C A 66, 61550p (1967). (126) Ketchum, D. F., Johnson, H. E. P., Microchem. J . 11, 139 (1966). (127) Kevei, E., Blazovich AI., Elelmiszervizsgalati Kozlemeny 10, 136 (1964); CA 64,11845 (1966). (128) Khadeev, V. A., Khalikova, F. Kh., Koroleva, V. I., .l'auchn. Tr., Tashkentsk. Cos. Univ. KO.264,3 (1964); CA 65,11341h(1966). (129) Khadeev, V. A., hlukhamedzhanova, D. M., Ibzd., 18 (1964); CA 65,113419(1966). (130) Khadeev, V. A., Tuyakov, N. B., Zbzd., 33 (1964); C A 65, 11344b (1966). (131) Khodakov, Yu. S., L'vov, A. hI., Zavodsk. Lab. 32,678 (1966). 132) Kim, H. R., Choe, K. O., Chosun Kwahakwon Tongbo 1965 (4), 26; CA 67, 78710j(1967). 133) Klopp, G., Papp, J., Meszaros, J., Magy. Kem. Lapja 21, 325 (1966). 134) Kniewald, J., hlildner, P., hIarkovic T., Arhiv. Tehnol. 3,117 (1965). 135) Kolthoff, I. SI., Shore, W. S., I
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Aparsheva, RI. I., Shvyrkova, L. A.,
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400R
TT
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ANALYTICAL CHEMISTRY
0
( 1 6 3 ) Marunina, A. T., Popel, A. A., Uch. Zap. Kazansk. Cos. Univ. 124, 203 ( 1 9 6 4 ) ; C A 6 4 , 1 1 8 3 3 ~(1966). ( 1 6 4 ) Mar’yanov, B. M., Zh. Anal. K h i m . 2 2 , 5 (1967). ( 1 6 5 ) Maslova, I. N., Esikov, A. D., Zavodsk. Lab. 31, 1270 (1965). ( 1 6 6 ) Matrka, M., Marhold, J., Collection Czech. Chem. Conimun. 30, 3202 (196.5). ( 1 6 7 ) Melkonyan. L. G., Bagdasaryan, R. V., Bunyatyants, Zh. V., Armyansk. K h i m . Zh. 19, 402 (1966); C A 66, 3475, (19671. ( 1 6 8 ) Michalski, E., Gelowa, H., Chem. Anal. ( W a r s a w ) 12,147 (1967). ( 1 6 9 ) Rlichalski, E., Pawluk, N., Ibid., 11,917(1966). ( 1 7 0 ) RIichal\ki, E., Pawluk, N., Lodz. Tow. ‘\‘auk.. Wudz. I I I . Acta Chint. 11. 39 ( 1 9 6 6 f : C A 66. 91i37s (1967). ( 1 7 1 j Michalski, E., Stapor, kl Ibid., p. 25 ( 1 9 6 6 ) ; C A 66,722712 (196:). ( 1 7 2 ) Michalbki. E., Wtorkowska-Zaremba, A., Ibid., 25, 45 ( 1 9 6 6 ) ; C.4 66.91399~11967l (173j Mill~r,J. W., Encycl. Znd. Chem. Anal. 1,489 (1966). ( 1 7 4 ) Rlittal, 11. L., Saxena, R. S.,J . Inorg. AVucl.Chem., 27, 2363 (1965). ( 1 7 5 ) Mittal, RI. L., Saxena, R. S., Indian J . Chem. 4 , 4 5 0 (1966). ( 1 7 6 ) Mlodecka, J., Chem. Anal. ( W a r saw) 10,861 (1966). ( 1 7 7 ) RIonnier, D., Arch. Sci. (Geneva) 18,273 (1968). ( 1 7 8 ) RIonnier, D., Delpin, G., Haerdi, W., Anal. Chim. Acta 35, 231 (1966). ( 1 7 9 ) Moroi, K., Ogawa, K., Ishii, Y., Bull. Chem. SOC. J a p a n 38, 1176 (1965). ( 1 8 0 ) Alukharnedshina, R. A., Churnachenko, 11. N., Uzbeksk. K h i m . Zh. 1966,22; C d 65, 17188e (1966). ( 1 8 1 ) Nukherji, A. K., J . Electroanal. Chem. 13,425 (1967). ( 1 8 2 ) Murea, L., Beral, H., Cuciureanu, E., Madgearu, X I Rev. Chim. (Bucharest) 16, 600 (1965). ( 1 8 3 ) Ibid., 17,46 (1966). ( 1 8 4 ) Rlurea, L., Rladgearu, RI., Cuciureanu, E., Beral, H., Ibid., 372 (1966). ( 1 8 5 ) llurtazaev, A. M., Bazarbaev, A-T., Khabibullina, Z. T., Tr. Tashkent. Farmatsevt. Inst. 4 , 365 ( 1 9 6 6 ) ; CA 67,676742 (1967). ( 1 8 6 ) hlurzakaev, F. G., Lab. Delo 1966, 148. 1187) Musha. S.. Ikeda. S.. Bunseki Kugaku 14,’793 (1965). ( 1 8 8 ) Xazrullaev, S. N., Gengrinovich, A. I., Murtazaev, A. Ll., Dokl. Acad. ,Yauk Uz. SSR 22. 23 ( 1 9 6 5 ) : CA 6 3 , 13336g (1965). ( 1 8 9 ) Negoiu, D., Gagescu, D., Studii Cercetari Chim. 14. 12.57 (196.5). ( 1 9 0 ) Nepeina, L. k,T;. Inst. Geol. i Geojiz., Akad. h’auk SSSR, Sibirsk. Otd. No. 32, 61 ( 1 9 6 5 ) ; C A 64, 7337c (1966). 191) Sovak, J. V. A., Collect. Czech. Chem. Commun. 30, 2703 (1965). 192) Novak, V., Proc. A n a l . Chem. Conf. Budapest, Hungary, April 1966, 225; ,4nal. Abstr. 14, 5233 (1967). 193) Novak, V., Collect. Czech. Chern. Commun. 32,2080 (1967). 194) Novak, V. P., llal’tsev, V. F., Odon, S.I., Zavod. Lab. 32, 1322 (1966). 193) Novak, V. P., Reznik, B. E., LIal’tsev, V. F., Z h . Anal. K h i m . 20, 827 (1965). ( 1 9 6 ) Ibid., 22,638 (1967). ( 1 9 7 ) Kovoshinov, G. P., Kashafutdinov, G. A., Uch. Zap. Kazan. Vet. Inst. 95, 306 ( 1 9 6 6 ) ; C.4 66, 61448m (1967). ( 1 9 8 ) O’Dom, G., Fernando, Q., AXAL. CHEX38,844 (1966). ( 1 9 9 ) Olsen, E. I) Walton, R. D., J . Chem. Educ., 43, $59 (1966). ,
~
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(200) Ospanov, Kh. K.,, Rozhdestvenskaya, Z. B., Sb. Statez Aspir. Soiskatelei, A f i n . V yssh. Sredn. Spets. Obrazov. K a z . SSR, K h i m . Tekhnol. 1965, 216; C A 6 6 , 2 5 5 8 3 ~(1967). ( 2 0 1 ) Pantani, F., Omagiu Raluca Ripan. 1966,419; C A 67,60668s (1967). (202) Panteleeva, E. P., Zavod. Lab. 32, 921 (1966). ( 2 0 3 ) Pardue, H. L., RIeans, D. K., ANAL.CHEM.,38, ,526 (1966). ( 2 0 4 ) Pashchenko, A. I., Songina, 0. A,, Kargina, N. I., Zavod. Lab. 31, 1312 (1965). (205) Pataky, B., Mitt. Klosterneuburg, Ser. A . 15, (4), 199 ( 1 9 6 5 ) ; C A 63, 18991d (1963). ( 2 0 6 ) Pavlova, I. XI. Abetova, E. K., Sb. Statei Aspir. Soiskatelei, M i n . Vyssh. Sredn. Spets. Obrazov. Kaz. SSR, K h i m . K h i m . Tekhnol. 3-4, 298 ( 1 9 6 j ) ; C A 6 6 , 111280y(1967). ( 2 0 7 ) Pavlova, I. >I., Songina, 0. A., Ibid., 3-4, 218 ( 1 9 6 5 ) ; C A 66, 101394% (1967). ( 2 0 8 ) Pavlova, I. SI., Songina, 0. A., Izv. Akad. ,\‘auk. K a z . SSR, Ser. K h i m . 17, 33 ( 1 9 6 7 ) ; C A 67, 87484r (1967). ( 2 0 9 ) Pinxteren, J. A. C. van, Verloop, 31. E., Pharm. U’eekblad. 99, 1125 (1964). ( 2 1 0 ) Ibid., 100, 189(1965). ( 2 1 1 ) Plazzogna, G., Pilloni, G., Anal. Chim.Acta 37,260 (1967). ( 2 1 2 ) Podolenko, A. A., Izv. Akad. A’auk Moldavsk, SSR, Ser. Biol i K h i m . iVauk 1964,73; Cd 64,18408b (1966). ( 2 1 3 ) Podurovskaya, 0. SI., Bogdanova, N. I., Beskova, G. S., Chizhov, L. V., Zavod. Lab., 32, 1455 (1966). ( 2 1 4 ) Popa, G., Cruceru, D., Bainlescu, G., Greff, C., Rev. Chim (Bucharest) 16,321 (1965). ( 2 1 5 ) Popovici, V., Schweiger, B., Spitzer, E., Acta Pharm. Hung. 35, 252 (1965). ( 2 1 6 ) Posgay, E., Ibid., 34, 1.52 (1964). ( 2 1 7 ) Protsenko, V. A., Zh. iVeorg. K h i m . 12,824 (1967). ( 2 1 8 ) Pryszczewska, XI., Proc. Anal. Chem. Conf. Budapest, Hungary, April 1966, 256; Anal. Abstr. 14, 5233 (1967). ( 2 1 9 ) Pryszczewaka, AI., Talanta 13, 1700 (1966). ( 2 2 0 ) Pucher, S., Zem.-Kalk-Gips 18, 530 (1965). ( 2 2 1 ) Ibid., 19,282 (1966). ( 2 2 2 ) Iiahman, S . LI. F., Malik, A. U., Z. ‘lnorg. Allgem. Chem. 335,217 (1965). ( 2 2 3 ) Ramachandran, S.,Naturajan, S. Ii., J . Electroanal. Chem. 1 1 , 230 (1966). ( 2 2 4 ) Rao, 11. S., Sudheendranath, S.
K. Ii., Rao, 11. B., Anantakrishnan, C. P.. Indian J . Dairu Sci. 18. 31 (1965). (223j Reddy, D. V., Rao, S. B., Chemist-
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9
(236) Saxena, R. S.,Sharma, 0. P., J . I n d i a n Chem. Soc. 42, 449 (1965). (237) Saxena, 11. S., Sharma, 0. P., Z. Anal. Chem. 212,286 (1965). (238) Saxena. li. S.. Sharma. 0. P., Eiperzentza22,104 ('1966). ' (239) Ibzd., 383 (1966). (240) Saxena, li. S., Sharma, 0. P., J . Inoro. ,Yucl. Chem. 28, 193 (1966). (241) Saiena, 11. S., Sharma, 0. P., I n d i a n J . Chem. 5 , 9 (1967). (242) Schiweck, H., Zucker 19, 396 (19%). (243) Schonberger, E., Studia Univ.BabesBolyui, Ser. Chem. 11, 147 (1966). (244) Schubert, K. D.,. Bergakademie 17, . 3#59(1965). (245) Schulz, K., G2as.-Instruni.-Tech. 10, 889,895 (1966). (246) Schulze, F., ANAL. CHEM.38, 748 (1966). (247) Senkevich, V. V., Soroka, A. A., Podolenko, A. A., Izv. Akad. S a u k Moldavsk. SSR, Ser. Biol. a Khirn. S a u k 1964, 61; CA 64, 8907b (1966). (248) Shafran, I. G., Iiozenblyum, V. P., Tr. Vses. Saz~chn.-Issled. Inst. K h i m . \ -
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Reaktzvov a Osobo Chistykh K h z m . Veshchestv KO.27, 207 (1965); C d 65,
6293a (1966). (249) Shafran, I. G., Rozenblyum, V. P Pnvlova 11. V..Ibid.. 138 1196,5), -- C A 65, 6294$ (1966): (250) Sharipov, 11. K., Sb. State2 Aspzr. Soaskatelii, J l in. Vyssh. Sredn. Spets. Obrazov. K a z . SSR, K h z m . K h i m . T e k hnol 3-4. 223 11963): C A 67, 77457, I
(1967).
(251) dharipov, R . K., LIokrousova, V., I b z d , 3-4, 302 (1963); C d 66, 990560 (1967). (252) Sharipov, li. K., Songina, 0. A., K h i m . z K h i m . Tekhnol., Alma-Ala, Sb. 2, 278 (1964); CA 64, 135Od
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