Amperometric Titrations

electrode (r.p.e.) and electrodes of other solid metals, especially aluminum and tantalum as compared with the dropping mercury electrode (d.m.e.). As...
3 downloads 0 Views 990KB Size
Download PDF
Review of Fundamental Developments in Analysis

Amperometric Titrations H. A. Laifinen, Universify o f Illinois, Urbana, 111.

P

ROGRESS during

the period since the last review (70) (October 1, 1959, to October 1, 1961) has been steady. Koticeable trends have been toward a diversification of indicator electrode reactions and toward a greater emphasis on the use of the rotating platinum electrode (r.p.e.) and electrodes of other solid metals, especially aluminum and tantalum as compared with the dropping mercury electrode (d.m.e.). As in the last review, amperometric titrations with two indicator electrodes will be designated as biamperometric titrations, and potentials of single indicator electrodes will be referred to the saturated calomel electrode (S.C.E.) unless otherwise specified. Several review articles have covered various phases of amperometric titrations, including biamperometric (59, 1 0 1 , l l J ) . solid electrodes (lid), organic applications ( I l l ) , and organic reagents ( I & $ , as well as reviewing the general field (70, 79,109,141). The theory of biamperometric titrations has been covered in several papers (60, 100, 113, l a $ ) , and the calculation and interpretation of titration curves have been covered in several others ( 16,39,53).

the electrode has been applied to the titration of fluoride Kith aluminum(II1) (68). The rotated dropping mercury electrode (r.d.m.e.) has been found as sensitive as the rotating platinum electrode (115). Biamperonietric titrations involving the use of two hanging mercury drop electrodes, using an applied a x . signal (61) or constant applied potential (86), have been described. Various examples of a x . “polarization titrations,” including redox, precipitation, and neutralization reactions, have been discussed by Morisaka and Harada (85). Visvanathan, Sundararajan, and Narayanan (142) have described a new “redoxokinetic” titration, in which an alternating potential is applied across two platinum electrodes and the end point is marked by a sharp change in d.c. potential. This method is not, strictly speaking, an amperometric method, but it is mentioned here for the purpose of comparison. Acid-base titrations using quinhydrone electrodes, and redox titrations involving irondichromate and arsenite-iodine reactions, proved successful, whereas the silver chloride precipitation reaction did not.

APPARATUS AND METHODOLOGY ION COMBINATION REACTIONS

Several different metals were investigated by Musina and Songina (84) as possible amperometric indicator electrodes, using H2S04 (pH = l), HOAc (pH = 4), NH4C1 and NaOH (pH = lo), NaOAc and NaOH (pH = lo), and NaOH (pH = 12). Copper was found unsuitable in both anodic and cathodic regions because of surface effects; silver was suitable for iodide titrations but became coated with oxide a t potentials above 0.4 volt; tungsten and tantalum were reported as completely unsuitable. Khadeev and Obel’chenko (58)’ on the other hand, found that rotated tantalum microelectrodes gave more stable anodic diffusion currents than platinum electrodes for a number of organic substances, notably EDTA, ascorbic acid, and 1-nitroso-%naphthol. Several applications have been made (54-66, 165). Amperometric, voltammetric, and potentiometric studies of the rotated aluminum electrode have been continued by Kolthoff and Sambucetti (67), and

Songina (110) was able to titrate chloride with silver in the presence of large amounts of copper sulfate by adjusting the applied potential of the r.p.e. so that copper was not deposited. Price and Coe: using a biamperometric end point with silver wires coated with silver chloride, determined small amounts of chloride in titanium or zirconium (93) and in paper or water (94). Iodide has been used as a precipitant for thallium(1) (81) and for bismuth (111) as the basic iodide, BiOI (97). Using the anodic current of iodide a t +0.6 volt (us. S.C.E.) a t the r.p.e., Zakharov, Songina, and Terzeman (151) titrated mercury(I1). Kolthoff and Sambucetti (67, 68) have continued their studies of the rotated aluminum electrode as an indicator electrode for fluoride titrations. They recommend titration with A1(NOs)3 a t pH 4.0 in 50% ethanol in the presence of 0.5M NaN03 or KNOs.

Under these conditions, a molar ratio of 5.9& 1 for F to A1 was observed over a fivefold concentration range. Aarts ( 1 ) used an iron(II1) fluoride titration with the r.p.e., previously described by den Herder and van Pinxteren (&), down to fluoride concentrations of 3 to 8 X 10-4Jf. Mal’tsev and Kovak (73) titrated fluoride in etching baths with iron(III), using the r.p.e. For free fluoride the titration was carried out a t pH 5 to 6, whereas for total fluoride the solution was made alkaline with NaOH. Yamashita (148) titrated with La(YOJ3 to precipitate fluoride tied up with iron(II1) in 50% ethanol a t pH 2.5 to 3.6. At the potential of the S.C.E., the current (due to liberated iron 111) gradually increases. Vasil’ev and Marunina (1.40) used the titration of copper(I1) with thiocyanate in the presence of 0.1 to 0.4M pyridine to form a complex precipitate. The precipitate is soluble in acids and in ammonia; hence ammonia is neutralized with acid and acids are neutralized with pyridine prior to titration. Ferrocyanide titrations have been applied to the determination of zinc in aluminum alloys (as),after tying up iron and aluminum as citrate complexes. Cadmium was titrated with ferrocyanide in the presence of Ni(II), Co(II), and Bi(III), using 0.2M potassium citrate (99), with the d.m.e. a t -1.80 volts. Manganese was titrated in the presence of glycine, using the r.p.e. with an applied potential of $0.4 volt (121). Magnesium was similarly titrated with ammonium ferrocyanide in 50y0 ethanol a t p H 6 to 9 (6). Ferricyanide was applied to the titration of bismuth(II1) in dilute nitric acid solution (8). Chloride and tartrate, which render the bismuth precipitate soluble, must be absent. A procedure for the determination of cobalt in magnetic alIoys, by precipitation with ferricyanide, has been described (124). Copper must be removed by electrodeposition or precipitation as sulfide, but nickel, iron, and aluminum do not interfere. The precipitation of ferricyanide with electrolytically generated silver(I), using polarized silver electrodes t o detect a biamperometric end point, has been described by Paunovi6 (90). Precipitation of lead molybdate or tungstate has been applied to the determination of molybdenum and tungsten VOL. 34, NO. 5, APRIL 1962

0

307 R

in steels (25). A biamperometric method, using the osidation current of lead a t a platinum electrode in an acetate buffer, was used. A similar titration was applied in the presence of nickel (9) after the addition of glycine or ethylenediamine to complex the nickel. The anodic oxidation of lead (11) in acetate solution has been studied as a function of pH (57). With the r.p.e., using an applied potential of 1.0 volt, L-shaped titration curves were obtained for the titration of lead with dichromate. The method was applied to the analysis of lead bronze. A molybdate titration of thorium has been applied to the analysis of monazite (129). Iron(II1) can be titrated with N a H r Po4 to form FeP04, using the r.p.e. with the S.C.E.17-ithout external e.m.f. (120). A glycine buffer (pH 3.4 to 3.6) is useful to prevent interferences. A titration of magnesium a t pH 10.5 in an ammonia-ammonium ion buffer t o precipitate MgNH4P04, using Na2HPO4 as the reagent, and the r.p.e. R-ith an applied potential of 1.9 volts has been described (103). The indicator electrode reaction is not clear from the abstract. The direct amperometric titration of potassium with tetraphenylborate, taking advantage of the anodic reaction of the reagent anion a t a graphite anode, has been developed by Smith, Jamieson, and Elving (108). An acetate buffer of pH 5 and an applied potential of +0.55 volt are recommended. The use of sodium selenite as a reagent for the precipitation of lead and copper from ammonium acetate medium has been described (32). The end point is marked by a minimum in the titration curves. Indirect determinations of silver(I), lead(II), and mercury(I1) based on precipitation of their selenites and amperometric titration of the filtrates with hypobromite have also been described. A direct amperometric determination of cobalt(I1) by titration with potassium tellurite, with the d.m.e. a t - 1.5 volts, has given good results over a concentration range of 0.1 to lOmM in 10% ethanol (31). Manok and Kelemen (74) determined carbonate in solutions of alkali metal hydroxides by precipitation with barium ion. The diffusion current of barium ion or, alternatively, that of chromate added as an indicator ion, was observed. Alcohol was added to lower the solubility of BaCOs. Bogovina and Selivanov (20) described an amperometric titration of boric acid (0.02M) in the presence of mannitol, using a rotating platinized platinum electrode. Strong mineral acids can be neutralized beforehand to avoid interference, but weak acids cannot be present. The use of an ampero308 R

ANALYTICAL CHEMISTRY

metric end point for acid-base titrations of pyridine nith perchloric acid or acetic anhydride in nonaqueous solution has been mentioned, but no details are available (150). Several applications of ethylenediaminetetraacetic acid [ (ethylenedinitri1o)tetraacetic acid, EDTA] titrations have appeared. Guerin (44) studied a variety of factors, such as the nature of the electrodes and electrochemical systems, p H effects, secondary complexation, and type of electrical circuit on potentiometric and amperometric titrations with EDTA. Mechelynck and Schietecatte (78) determined the solubility of EDTA as a function of pH by means of an amperometric titration with ammoniacal zinc(I1) solution. Application of EDTA titrations can be subdivided for convenience into three groups. In the first group, the end point is detected by observing the diffusion current due to a metal ion, either aquated or complex. Esamples in this group are the determination of aluminum by the addition of excess EDTA which is back-titrated with iron(II1) (r), titration of gallium in Gap04 dissolved a t pH 1.5 to 2.5 (26), and determination of indium in sphalerite concentrates (128). An indirect determination of cadmium by addition of a solution of mercury(I1)EDTA to displace mercury(II), which is then titrated with standard EDTA using two mercury drops polarized with a low frequency alternating voltage, can also be placed in this group (61). I n the second group of applications, the indicator current is due to anodic oxidation by EDTA. The anodic oxidation current a t a platinum indicator electrode hss been applied to the titration of zinc in cobalt plating baths after the separation of zinc by fusion with KOH (50), to the titration of EDTA with copper(I1) (65),t o the determination of iron in ores by titration of iron (111) (157), and to the titration of vanadium(II1) and (IV) (126). The latter determination is based on the fact that V+3 forms a more stable EDTA complex than VO+2. I n H2S04solution a t pH 1.0 to 2.5 only V+3 is titrated, whereas a t pH 3 to 4 two separate breaks are observed, the first due to V f 3 and the second to VO+2. A biamperometric titration with two platinum electrodes polarized with an applied voltage of 1.48 volts a t pH 2 to 3.5 has been applied to the titration of thorium(1V) with EDTA (88). The indicator reaction no doubt involves the anodic osidation of EDTA. A tantalum electrode has been found superior to platinum for the titration of bismuth(II1) in 0.1 to 0.5M acid with EDTA (155). Similarly, zirconium(1V) was titrated in HzS04, “ 0 3 , or HC1 medium (56) using a tantalum electrode.

The other types of EDTA titration, involving the anodic depolarization wave of mercury and the use of an amperometric indicator, are much less frequently used, although both found application in an analysis of a mixture of bismuth, aluminum, calcium, and magnesium salts by Weng and Li

(144). OXIDATION-REDUCTION REACTIONS

Methods Based on Iron. An assay method for chromium metal or chromium(II1) oxide, based on oxidation to chromium(V1) nith peroxydisulfate followed by the addition of excess solid RIohr’s salt and amperometric titration of the excess iron(I1) with dichromate, has been found to be accurate to within 0.17, (51). For the titration of low concentrations of iron(I1) with cerium(IV), Kolthoff and Bhatia (64) found ferroin useful as an amperometric indicator. Selim and Lingane (lob), in studying the coulometric efficiency of the osidation of Mn(I1) to Mn(III), used an amperometric end point in 5111 H2S04in titrating hln(II1) with iron(I1). I n sufficiently concentrated sulfuric acid, such as mixed nitration acid, a biamperometric titration with iron(I1) was found useful in the determination of nitric acid or nitrate esters such as nitroglycerin or nitrocellulose (145). Farrington, Schaefer, and Dunham (38) used an amperometric end point in the coulometric titration of iron(1Ii with electrolytically generated chlorine. illahr and Seeger (71) determined copper by titration with iron(II), taking advantage of the fact that fluoride shifts the potential of the iron(II1)iron(I1) couple to make the reaction Fe+2 Cu+2 I-+ Fe+-3 CUIquantitative. The biamperometric titration gave slightly low results, and the authors therefore preferred a potentiometric end point. Ferricyanide has been used as an oxidant by several investigators. Bozsai (21) determined cobalt in alloys and silicates by oxidizing cobalt(I1) to a cobalt(II1) amine n-ith ferricyanide in the presence of ammoniacal tartrate. An excess of osidant was added and back-titrated using the r.p.e. a t zero applied e.m.f. The same method was applied to cobalt in steels and alloys (22). A similar titration, using citrate to prevent the interference of lead and bismuth, or tartrate to prevent the interference of iron, chromium, and copper, was applied by Zhdanov and coworkers (154). A coulometric determination of chromium, based on the oxidation of chromium(II1) with electrolytically generated ferricyanide in strongly alkaline solution, has been described (7‘6). A biamperometric end point was used.

+

+

+

Furman and Fenton (41) showed that alkaline ferricyanide can be titrated accurately with cerium(II1) in oxygenfree solution, using either one or two indicator electrodes. The one-electrode system was preferred because of its more nearly linear response. Indirect determinations of many substances that react slowly with excess ferricyanide in alkaline solution were suggested. An interesting indirect amperometric method was suggested by Czarnecki (27) for the determination of microgram quantities of copper. Copper catalyzes the reaction between iron(II1) and thiosulfate to form iron(I1) and tetrathionate. The rate of the catalyzed reaction was determined by measuring the initial and maximum currents passing between polarized platinum electrodes. Methods Based on Halogens. Hollo and coworkers (47) compared amperometric, potentiometric, and photometric methods for determining iodine absorption by starch, and concluded that the accuracy decreased in the order listed. The potentiometric method gave somewhat lower results than the amperometric. Barkley and Thompson (14) compared the amperometric and catalytic methods for determination of total iodine and combined (iodate) iodine in sea water. The catalytic method, based on a spectrophotometric (brucine) method of determining the reaction rate of the arsenic (I1I)-cerium (IV) reaction catalyzed by total iodine, proved to be somewhat more rapid and accurate than the amperometric method. In the latter, iodate was determined by adding first an excess of iodide, then an excess of thiosulfate, which was titrated with standard iodate. Total iodine was determined by first oxidizing iodide to iodate with bromate. Concentrations as low as 5 pg. per liter mere determined nith a standard deviation of 2.1 pg. The catalyzed cerium(IV)-arsenic (111) reaction has been applied (28) to the determination of small absolute amounts of iodine (0.12 to 0.76 pg.), with an amperometric determination of reaction time. Small quantities of selenium have been determined by addition of an excess of thiosulfate to reduce Se(1V) to Se(O), followed by titration of the excess thiosulfate with iodine (49). A coulometric titration of arsenic(II1) with electrolytically generated bromine has been found to give a more nearly linear relation between current and arsenic concentration with an amperometric than a potentiometric end point (119). The titration of antimony(II1) with bromate has been described as a simple, accurate, and rapid method for determining antimony

in bearing metals, bronze, and brass (42). The titration of hydrazine with bromate, using the r.p.e. at 0.0 volt in 251 HC1-0.05M KBr, has proved accurate within 1% for 3-mg. samples and within 5% for 30-pg. samples (98). For the determination of microgram quantities of bromate, Arcand (4) added an excess of bromide to give bromine, which was titrated coulometrically with electrolytically generated copper(1). -4 biamperometric end point led to an error of 0.3 pg. independent of sample size over the range 18 to 240 pg. Berraz, Cerana, and Delgado (18) described an indirect determination of sulfate, based on the reaction of barium chromate with sulfate in hot acid solution to liberate dichromate, which was determined by adding an excess of standard arsenic(II1) and back-titrating with bromate to a biamperometric end point. -4hypobromite titration of selenium (IV) in bicarbonate solution, using the r.p.e. a t 0.3 volt, has been applied by Deshmukh and coworkers (33) to the indirect determination of silver(I), lead (11), and mercury(I1) through the precipitation of their selenites and analysis of the filtrates. A similar hypobromite titration has been applied to the oxidation-titration of antimony(II1) and thiocyanate (34). A titration of bleaching powder has been carried out with 0.1W arsenite in bicarbonate medium, using an amperometric observation of end point with a platinum anode and tungsten cathode (162). Bastin, Siegel, and Bullock (16) have described an apparatus for the determination of small amounts (0.01 to 3 mg.) of water by the Karl Fischer titration with a biamperometric end point. Zhdanov, Khadeev, and Yakovenko (166) determined cobalt by adding an excess of iodine to an ammoniacal solution of cobalt(I1) to form iodopentammine cobalt(II1) ion. The excess iodine was back-titrated amperometrically with arsenic(II1). Other Redox Titrations. The use of electrolytically generated uranium (V) R R a reductant is limited by the fact t h a t the rate of disproportionation of U(V) to give U(V1) and U(IV) increases in acid solution, and U(1V) is often slow t o react. By adjusting the p H to 1.5 to 2.0, Phillips and Kern (91) were able to perform accurate coulometric titrations of vanadium(V) using biamperometric end point detection. This method is especially suitable for determination of vanadium in the presence of large amounts of uranium. Using electrolytically generated titanium(III), uranium(V1) was titrated amperometrically to uranium(1V) (56). In a mixture of vanadium(V) and

uranium(VI), two end points were observed, the first corresponding to the reduction V(V) --+ V(1V) and the second to the simultaneous reductions V(1V) 4 V(II1) and U(V1) + U(ITT). The method was accurate to within &0.3% for uranium-vanadium ratios betn-een 0.1 and 10. A titration of uranium(1V) with ammonium vanadate in 12N HzS04 to give uranium(V1) and vanadium(1V) has been applied to the determination of uranium in ores, waters, and production bolutions (37). An amperometric titration of vanadium(V) &,h ascorbic acid in 0.1JI H2S04, observing the oxidation current of the reagent a t +0.925 volt a t the r.p.e., has been studied by Sin& (105). Davis and Lingane (SO) showed that electrolytically generated silver(I1) could be applied t o the oxidation of oxalic acid, cerium(III), arsenic(111), or vanadium(1V) using amperometric or potentiometric end points. Gold electrodes gave a higher current efficiency than platinum, and titration a t 0' increased the current efficiency by enhancing the stability of silver(I1). Manganese (11) and chromium(II1) could not be titrated directly. Kitagawa (63) used an amperometric end point a t an applied potential of 0.35 to 0.75 volt for the titration of manganese(I1) with permanganate in the presence of sodium triphosphate as a complexing agent to stabilize manganese(II1). Ism, Issa, and Allam (48) titrated tellurite n-ith permanganate, in alkaline solution, observing either reversed L-shaped curves a t -0.8 to -1.0 volt, or V-shaped curves a t -1.4 volts. Bard and Lingane (12) used amperometric, potentiometric, and spectrophotometric end points for the titration of gold(II1) with electrolytically generated tin(I1). X rapid amperometric determination of cerium in loparite, l m e d on decomposition of the mineral n-ith NHIF and HzSO4, oxidation of the cerium with bismuthate, filtration, and titration with vmadyl sulfate, has been described (153). The r.p.e., a t a potential of fO.6 volt, served as an indicator electrode. TITRATIONS INVOLVING ORGANIC REAGENTS

Khadeev and Glazunova (55) applied the rotating tantalum electrode to amperometric titrations with 1nitroso-2-naphthol as a reagent. Copper(I1) gave the Lest results, nith either a cathodic current a t -0.3 volt or an anodic current a t 0.9 volt. Cobalt(I1) could not be determined; palladium gave less accurate results than copper. Szmidt and Weber (118) developed a procedure for cobalt in steel involving an amperometric titration with 1-nitroso-2-naphthol. VOL. 34, NO. 5 , APRIL 1962

309R

Berraz, Delgado, and Vassallo (19) studied the titration of pairs of cations (Fe-A1, Cu--21, Cu-Zn, and A1-Mg) with 8-quinolinol, in each case using a suitable buffer to precipitate the first component, then raising the pH t o precipitate both components. Dibromoquinolinol has been used as a reagent for the titration of iron, titanium, and copper, and applied to the determination of copper in aluminum alloys (89). Csing tritium-labeled anthranilic acid, hylward and con orkers (61 found identical results using radiometric and amperometric end points in the titration of copper(I1). Lsatrnko and Tulyupa (134) used sodium diethyldithiocarbamate as a reagent for copper(I1) and mercury(II), taking advantage of the anodic oxidation of a soluble lead(I1) complex of the reagent a t an applied potential of 0.8 to 0.9 volt to detect the end point. The method was applied to the determination of copper in steels (135). The same authors (136) described a selective estraction of zinc and cadmium (together with lead), using ethyl acetate as the estractant for the diethyldithiocarbamates from a IAIrHC1 solution. After lead has been removed by precipitation as the sulfate or chromate, cadmium can be selectively precipitated in strongly ammoniacal solution. After acidification and adjustmcnt of pH the zinc can be titrated. The method was applied to cadmium and zinc determinations in aluminum alloys and sulfide ores containing copper. Kickel diethyl dithiophosphate has been used as a titration reagent for lead in nitric acid solution ( 3 ) . The method is applicable over a wide range of acid concentrations, but the most accurate results are obtained between 0.25iV and lN nitric acid. Many heavy metals interfere. Zhdanov, Khadeev and Ehamakhmudova (156) found the r.p.r. more sensitive than the d.m.e. for titration of microgram quantities of copper with rubeanic acid. Procedures mere n orked out for determination of copper in the presence of larger amounts of nickel, cobalt, iron, chromium, and bismuth. Yamamura, Rein, and Booman (24’7) titrated tin(1V) with cupferron in 231 H2S04-3A11(NHe!?S04, detecting the end point a t -0.84 volt nith the d.m.e. Ciipferron has been applied t o the titration of yttrium (139) and to the determination of titanium in steel (190) and zirconium in silicates (133), taking advantage of the anodic oxidation of the reagrnt a t the r.p.e. The same reagent was successfully used for gallium in the presence of aluminum or zinc (126). I n the titration of palladium with 310 R

ANALYTICAL CHEMISTRY

8-furfural oxime, Bardin and Meleka (13) used the r.p.e. The reagent gave no reduction current a t 0.9 to 1.0 volt in NaN03 containing 0.01M HC1, and an L-shaped titration curve resulted. Banerjea and Chakravarty titrated copper(II), using mandelamidoxime in an ammonia buffer a t pH 8 to 9 (ZI), or salicylamidoxime in an acetate buffer, using the d.m.e. (10). Wlson, Baye, and James (146) titrated palladium(I1) with 2-(o-hydroxypheny1)benzoxazole in an acetate buffer using the d.m.e. a t -0.5 volt. Iridium(1V) interfered but small amounts of other platinum metals could be tolerated. Usatenko and Bekleshoi-a (131) showed that silver(1) can be titrated even in 224 ammonia using the r.p.e., with 2-mercaptobenzothiazole as the reagent. Since chloride does not interfere, the method can be used for determination of silver in silver chloride. Copper(I1) can be titrated in several media, to yield a copper-reagent ratio of 1 : 2 o r 1:l. With palladium(I1) in milligram quantities, bismuthiol(1) yields a 1: 1 metal-reagent ratio (7W), whereas bisniuthiol(I1) and 2-mercaptohenzimidazole yield 1: 2 ratios. StevanEevi6 (112) found by means of precipitation titrations with quinoxaline-2,3-dithiol using the d.m.e. the following molar ratios of reagent to metal in their chelates: Cu, 2:1; Cd, 1:l; Bi, 2:l; Pb, 1 : l ; Ag, 1:l. Thioacetamide has been used as a titrant for silver(1) in buffers of pH 9.3 (96). Thioglycolic acid, electrolytically generated from its mercury(I1) complex, has been used as a reagent for mercury(II), gold (111), copper (11), and ferricyanide (82). With the latter two reactants thioglycolic acid acts as a reducing agent, with the formation of the disulfide. With gold(III), a twostep reaction involving reduction to gold(I), followed by complexation to form the gold(1) mercaptide, occurs. Thiourea has been used to titrate mercury and silver successively, taking advantage of oxidation of the reagent a t the r.p.e. for end point detection (133). Several organic reducing agents, pHOCBHIOH, P-K’H~C~H~OH, p-nTH2CsH4SH2, and (hleNHC6HeOH)zH~SOI, mere shown t o react quantitatively and selectively with gold(II1) in 2N HPSOd a t 50°, in the presence of selenium(IV), tellurium(IV), and platinum metals (96). The oxidation of the reagent a t the r.p.e. a t 1 volt was used as the basis of end point detection. Singh (105) has used ascorbic acid as a reductant for vanadium(V1, detecting the end point by oxidation of the reagent a t f0.925 volt a t the r.p.e. Swann, McKabb, and Hazel (117)

used the suppression of the polarographic wave of fructose a t -2.05 volts in 0.1M LiC1-0.01N LiOH by borate a s the basis of an amperometric determination of milligram quantities of boron. Sodium ion was removed by ion exchange to prevent its interference. Popa, Negoiu, and Baiulescu (92) titrated zirconium(1V) with tartrazine to form a stoichiometric precipitate. ”4 V-shaped titration curve with a minimum a t the end point was observed with the d.m.e. a t -0.9 volt. Masdk (75) used berillon [tetrasodium salt of 2-(8-hydroxy-3,5disulfo - 1 - naphthylazo) - 1,s - dihydroxy - 3,6 - disulfonic acid] as a precipitant for thorium(IV), detecting the end point with a d.m.e. a t an applied potential of -0.8 volt. Zirconium(1V) and rare earths interfered. Heyrovsk? (46) described the mercurimetric titration of B(CgH5)4-, (C&?& or (C&&BOH to form C G H ~ B ( O Hand ) ~ (CsHs),Hg. The latter reacts with more Hg(I1) ion to form CeH5Hg+. The reverse titration of Kg(I1) with B(CBH~)4-or C6H5B(OH)2 was also successful. DETERMINATION

OF ORGANIC COMPOUNDS

The observation, apparently first made by Sluyterman (106), that certain sulfhydryl compounds containing other functional groups which might act a# complexing groups give high results in titrations with silver nitrate has been confirmed by other workers (2, 65). Cysteine, in particular, has been found to give results about 25% high. Belitser and Lobachevskaya (179, in titrating sulfhydryl with silver nitrate in an ammonium nitrate-ammonia buffer, found that by adding 10% alcohol and 0.5M Ca(N03)zto the buffer, an “extra binding” of silver, presumably due to complex formation, was avoided. Singh (104)used tris(hydroxymethy1)aminomethane with 0.01M KC1 as a supporting electrolyte for argentimetric titrations. Stricks and Chakravarti ( f l 5 ) ,using the rotated dropping mercury electrode, found ethylmercuric chloride a useful titrant for small quantities of sulfhydryl in amino acids, peptides, and proteins. The amperometric method has found application for sulfhydryl determinations in glycinin (107), Myosin (123), and beer (23). Grafnetterova (43) used mercury(I1) chloride as a titrant for penicillin in a borate buffer. The method was applied, after a chloroform extraction treatment, to the determination of penicillin in urine. The biamperometric method has been used to follow the rates of diazotization of aromatic amines (77). Butt and Stagg (94, however, reported that the potentiometric method is superior in

Small concentrations of hydrobeing suitable for a larger number of amines, and less subject to interference peroxides (1O-bM) have been determined by adding a slight excess of from copper and iron salts. arsenic(II1) in alkaline solution and Acetaldehyde has been titrated with back-titrating the excess with peroxide hydroxylamine hydrochloride over a wide range of concentrations (138). (66). The oxime yields a reduction ware suitable for detection at E = -1.25 LITERATURE CITED volts. The use of 2,4-dinitrophenylhydrazine for the titration of aldehydes and ketones is normally of limited use because of the errors introduced by the suspended reaction product (2,4-dinitrophenylhydrazone). Zobov, Lyalikol-, and Mukhammednazarova (157') overcame this difficulty by coagulating the sediment with carbon black or by using ultrasonic waves. The method n as applied to the titration of benzaldehyde and citral. Ogawa (87) used silicotungstic acid as a sensitive precipitant for chrysoidine and safranine in 6N H2S04. Similarly, Yoshino and coworkers (149) titrated yohimbine with silicotungstic acid and phosphotungstic acid in dilute hydrochloric acid medium. KrAEmar (69) used the d.m.e. a t -0.4 volt to titrate 25- to 50-mg. samples of 3,4( 1,3-dibenzy1-2-ketoimidazolido) - 1,2 - trimethenethiophenium - d - camphorsulfonate in a BrittonRobinson buffer of p H 5.0 to 7.5 with 0.1M picric acid. Ascorbic acid has been used as a titrant for 2,6-dichloroindophenol (86). To determine ascorbic acid, Deshmukh and Eshwar (36)used chloramine T as the titrant in a citrate buffer, while Deshpande and Natarajan (36) used permanganate in the presence of KI and H2SO4. An iodometric method, using biamperometric indication of the end point of a thiosulfate titration, has been used (127) for the determination of pseudocumene hydroperoxide. Potassium bromate has found application to the determination of total phenolic groups in epoxy resins (40). .4 mixture of methanol and dimethylformainide M as used as the solvent, with 0 . 5 Z HCI as supporting electrolyte. Ci,rium(IV), added in twofold excess in 1N HC10, at 60' and backtitrated with oxalate, has been applied to the determination of glucose, fructose, and sucrose 180). Several organic reducing agents-metol, hydroquinone, p-aminophenol, and p-phenylenediamine-have been titrated with dichromate in 0.5 to 2.ON H2S04with platinum indicator electrodes (116), using an applied potential of 1 volt us. S.C.E. h titration of phenylmercuric acetate, based on the precipitation of phenyl(1961). mercuric iodide upon the addition of (29) Danilenko, E. F., Drabkina, A. K., Zavodskaya Lab. 26, 430 (1960); CA KI (85), has been applied to com54,15078 (1960). mercial tablets containing 1 mg. of (30) Davis, D. G., Lingane, J. J., Anal. phenylmercuric acetate. Chim. Acta 18, 245 (1958).

(31) Deshniukh, G. S.,h a n d , V. D . Joseph, A,, Z. anal. Chem. 180, 174

(1961). (32) Deshmukh, G. d., Asthana, 0 . P., J. Sci. Research Banarm Hindu Univ. 10,41(1959). (33) Deshmukh, G. S., Bapat, M. G., Balakrishnan, E., Eshwar, 111. C., 2. anal. Chem. 170, 381 (1959). (34) Deshmukh, G. S., Eshwar, M. C., Current Sci. (India)29,388 (1960). (35) Deshmukh, G. S., Eshwar, M. C., J . Sci. Research (India) 19B, 502 (1960). (36) Deshpande, S. Yl., Natarajan, R., J . Am. Pharm. dssoc. 47,633 (1958). (37) Eskevich, V. F., Komarova, L. A , Zhur. Anal. Khim. 15, 84 (1960). (38) Farrington, P. S.,Schaefer, Jt-, P., Dunham, J. hl., ANAL. CHEM. 33, 1318 (1961). (39) Ferreira de hIiranda, C., Rec. juc. cienc., Univ. Lisboa [2], B7, 113 (195960); CA 55,14157 (1961). (40) Flegontova, L. N., Ginzburg, V. S . , Lakokrasochnye Materialy i ikh Primenenie 1960, No. 5, 70; CA 55, 10951(1961). (41) Furman, N. H., Fenton, A. J., J r . , AXAL.CHEM.32,745 (1960). (42) Garate, M. E., Astudillo, R f . D., Burriel Marti, F., Anales real SOC. espafi. j i s . y quini. (Madrid) 56B, 775 (1960); CA 55,8157(1961). (43) Gpfnetterova, J., casopis 1Bkh-u ceskych 99, 182 (1960); C A 54, 2500 (1960). \ - - - - I -

(44) Guerin, G., Electroanal. Chem. 1, 226 (1960). (45) Herder, J. J. den, Pinxteren, J. A. C. van. Pharm. Weekblad 93, 1013 (1958). (46) Heyrovsk?, A., 2. anal. Chem. 173, 301 (1960). (47) Hollo, J., Laszlo, E., Szejtli, J., Mandi, *4.,Sturke, 12, 351 (1960); CA 55,8904(1961). (48) Issa, I. AT., Issa, R. M., Allam, M. G., Anal. Chim. Acta 23, 196 (1960). (49) Jensen, R., Chim. anal. 41, 394 (1959). (50) Kao, H. H., Hui, W., Pei Ching Tu Hsueh Hsueh Pao Tsu Jan K6 Hsueh 3, KO. 2, 217 11957): CA 54, 24125 (19691.. (51) keily, H. J., Eldridge, A., Hibbits, J. O., Anal. Chim.Acta 21, 135 (1959). (52) Kennedy, J. H., Lingane, J. J., Ibid., 18, 240 (1958). (53) Khadeev, V. A., Uzbek. Khim. Zhur. 1959, No. 2,27: C d 54,6390 (1960). (54) Khadeev, V. A., Bazarbaev 4. T., Uzbek. Kham. Zhiir. 1960, No: 5, 38; CA 55,8170 (19611. (55) Khadeev, V. A , , Glazunova, L. -4, Uzbek. Khzm. Zhur. 1959, No. 3, 24; CA 54,6402 (1960). (56) Khadeev, V. A,, Kvashina, F. F., Izzrest. Vysshikh Ucheb. Zavedenii, Khim. i Khim. Il'ekhnol.3, 251 (1960): C A 54, 20667 (1960). (57) Khadeev, V.A,, Tikurashina, A. G., Zavodskaua Lab. 25, 283 (1959); CA 54,18187"~1960). (58) Khadeev, V. A., Obel'chenko, P. F., Doklady Akad. Sui112 Uzbek. S.S.R. 1959, To. 6,31; CA 54,12839 (1960). (59) Kies, H. L , Anal. Chzm. Acta 18, 14 (1958). (60) Iiies, H. L., J . Electroanai. Chem. 1, S o . 2, 171 (1959). (61) Kitagawa, T., Bull. Chem. SOC. Japan 33, 1124 (1960); CA 55, 7157 (1961).

\ - - - - I -

(62) ,Kitagawa, T., Nippon Kugaku Zasshz 81,83 (1960). (63) Knight, W. S., Osteryoung, R. il., Anal. Chim.Acta 20,481 (1959). (64) Kolthoff. I. M.. Bhatia. B. B.. -&ficrochem.'J.4,451 (1960). ' VOL. 34, NO. 5 , APRIL 1962

31 1 R

(65) Kolthoff, I. X, Eisenstadter, J., Anal. Chim. Acta 24, 83 (1961).

(66) Kolthoff, I. M., Meehan, E., J., Bruckenstein. S.. Minato., H.., Mzcrochem. J . 4,33’(1960). (67) Kolthoff, I. RI., Sambucetti, C. J., Anal. Chim. Acta 22, 253 (1960). (68) Zbid., p. 351. (69) KrLhmar, J., ceskoslov. farm. 5, 578 (1956); C A 54,13986 (1960). (70) Laitinen, H. A., ANAL.CHEM.32, 180R 11960). (71) hlahr, d., Seeger, B., Z. anal. Chem. 171,343 (1959). (72) Majumdar, A. K., Chakrabartty M. &I., Anal. Chim. Acta 20, 386 (1959). (73) Mal’tsev. T’. F.. Novak. V. P.. ’ Zavodskava ‘ Lab. 25. 1296’ (1959). CA 54,3440 (1960). ’ (74) Manok, F., Keleman, SI.,Studia Univ. Babes-Boluai, Ser. 1, No. 2, 99 (1959); CA 55, 7151 (1961). (75) hlaskk, J., Chent. listy 52, 740 (1958); CA 54, 10670 (1960) (76) hIBtht5, I., Csathy, A., Richter, A., Acad. rep. populare Romine, Filiala Cluj, Studii cercetriri chim. 11, 83 (1960); CA 55, 9158 (1961). (77) hlatrka, M., VaniEek, V., Sbornik ved. praci, Vysoka skola chem.-technol. Pardubice 1959, 299; CA 54, 13832 (1960). (78) Mechelynck, P., Schietecatte, W., Anal. Chim. Acta 19,577 (1958). (79) Michalski, E., Wiadomofci Chem. 14, 411 (1960): CA 55. 6243 (1961). \

I ,

. .. 53,19760 (1959j. . (82) Miller. B.. Hume. D. N.. ANAL. ’ CHEM. 32,524( 1960). ‘ (83) Morisaka, K., Harada, T., Yakugaku Zasshi 80, 532, 537, 541 (1960); CA 54,18156 (1960). (84) Musina, T. K., Songina, 0. A., Uchenye Zapiski Alma-Atinsk. Gosudarst. Pedagog. Znst. 1957, No. 8, 174; C B 54,4200 (1960). (85) Nagase, Y., Iguchi, M., Yakugaku Zasshi 80, 1480 (1960); CA 55, 5871 114Plll ,-”--,.

(86) Ogawa, T., J. Electrochem. Soc. Japan (Overseas Ed.) 26,105 (1958). (87) Zbid., p. 134. ( 8 8 ) Palei, P. K., Udal’tsova, K. I., Trudy Komissii Anal. Khim., Akad., h‘auk S.S.S.R., Inst. Geokhim. i Anal. Khim. 1 1 , 299 (1960); CA 55, 10200 (1961). (89) Panteleevn, L. I., Nauch Zapiski L’vov Politech. Inst., Ser. Khim.-Tekhnol. 50, No. 3, 50 (1958); CA 53, 17750 (1959). (90) Paunovi6, M. M., Bull. sci. Conseil acad. RPF Yougoslavic 5, 98 (1960); CA 55,11175 (1961). (91) Phillips, S. L., Kern, D. hi., Anal. Chim. Acta 20,295 (1959). (92) Pooa. G.. Neeoiu, D.,‘ Baiulescu. . G., Zbid.; 22,200 (r960). (93) Price, D., Coe, F. R., Analyst 84, 55 (19593. (94) Zbid., p. 62. (95) Pryszczewska, M., Chem. Anal. (Warsaw) 5, 931 (1960); CA 55, 14172(1961). (96) Reishakhrit, L. S., Sukhobokova, N. S., Uchenye Zapiski Leningrad Gosudarst. Univ. A . A . Zhdanova No. 297, Ser. Khim. Nauk KO. 19, 150 (1960): CA 55.9159 (1961). (97) R i k u l , W.., Lodz. Towarz. Nauk Wgdzial ZZI No. 4, 65 (1960); CA 54,17152 (1960). (98) Sant, B. R., Mikherji, A. K., Anal. Chim. Acta 20,476 (1959).

312 R

ANALYTICAL CHEMISTRY

(99) Saraswat, H. C., Proc. Indian Acad. Sci. 51A, 34 (1960). (100) Savitskaya, I. S., Songina, 0. A., Zavodskaya Lab. 25, 647 (1959); CA 53,19664 (1959). (101) Savitskaya, I. S., Songina, 0. A., Zavodskaya Lab. 26, 282 (1960); CA 54,13940 (1960). (102) Selim, R. G., Lingane, J. J., -4nal. Chim. Acta21,536 (1959). (103) Shmelev, B. A., Danilova, E. N., Sbornik Nauch. Rabot Moskov. Znst. Narod. Khoz. 1957, No. 10, 335; CA 54,11843(1960). (104) Singh, D., J . Sci. Research Banaras Hindu Univ. 10,6 (1959-60). (105) Zbid., p. 56. (106) Sluvterman. L. A. E.. Biochem. et ‘ Biophyd. Acta 25,402 (1957). (107) Smirnova, T. I., Poglazov, B. F., Kretovich, V. L Biokhimiya 24, 758 (1959); CA 54,3;51(1960). (108) .Smith, D. L., Jamieson, D. R., Elvmg, P. J., ANAL.CHEM.32, 1253 f 1960). \ - - - - I -

(109) Songina, O. A., Zavodskaya Lab. 24,160 (1958). (110) Ibid., p. 273; CA 54, 10672 (1960). (111) Souchav. P.,. Chim. anal. 41, 471 (1959). 12) StevanEevi6, D. B., Bull. Znst. Nuclear Sci. “Boris Kidrich” (Belgrade) 9, 57 (1959); C.4 53, 17725 (1959). 13) Stock, J. T., Microchem. J . 3, 543 (1959). 14) Stock, J. T., Proc. Intern. Symposium Microchem., Birmingham Univ. 1958,402 (pub. 1959). 15) Stricks, W.,Chakravarti, S. K., ANAL.CHEM.33,194(1961). .16) Sukhobokova, N. S., Vestnik Leningrad. Univ. 15, No. 16, Ser. Fiz. i Khim. No. 3. 149 (1960): , ,, CA 55. 213 (1961). (117) Swann, W. B., McNabb, W. M., Hazel, J. F., Anal. Chim. Acta 22, 76 (1960). (118) Szmidt, K., Weber, J., Prace inst. Mech. 6, 71 (1957); CA 55, 219 (1961). (119) Takahashi, T., Sakurai, H., Bunseki Kabaku 7, 296 (1958); CA 54, 3046 1 .

(1960). \----I-

(120) Teodorovich, I. L., Abramov, M. Doklady Akad. Nauk Uzbek. F5.R. 1959, No. 1., 29:, CA 54, 5338 (1960). (1211 Teodorovich. I. L.. Abramov. M. ‘ K.’, Zavodskaya’Lab. 24, 406 (1958); CA 54,11843 (1960). (122) Tockstein, A., Komem, K., CoL lection Czechoslov. Chem. Communs. 24, 2328 (1959). 11231 Torchinskil. Y. M.. Ukrain. Bio‘ khim. Zhur. 31; 589 (1959); CA 54, 13204(1960). (124) Toropova, V. F., Strekalova, 0. S., Zavodskaya Lab. 24, 140 (1958); CA 54,8441 (1960). (125) Tserkovnitskaya, I. A., Kalinin, A. I., Morachevskif, Y. V., Zavodskaya Lab. 26, 797 (1960); CA 54, 20652 (1960). (126) Tserkovnitskaya, I. A., Kustova, N. A,, Vestnik Leningrad. Univ. 15, No. 16, Ser. Fiz. i Khim. No. 3, 148 (1960); CA 55,242 (1961). (127) Tsuk, L., Zollner, G., Magyar Ktm. Laaia 14. 417 (1959): . ., CA 54, 10644 (19gO). ‘ (128) Tsyvina, B. S., Vladimirova, V. M., Zavodskaya Lab. 24, 278 (1958); CA 54.11829 (1960). ,----,----,(129) Tung, S. C., Wang, E. K., Hua Hsiieh Hsueh Pao 25, 33 (1959); CA 54,10670 (1960). (130) Usatenko, Y. I., Bekleshova, G. E., Trudy Dnepropetrovsk. Khzm.-Tekhnol. Znst. 1958, No. 6, 32; Referat. Zhur., Khim. 1959, Abstr. No. 31003: CA 53,19701 (1959).

( 131i

Usatenko. Y. I.. Bekleshova, G. E.. Ukrain. Khim. Zhhr. 25, 512 (1959); CA 54,8469 (1960). (132) Usatenko, Y. I., Bekleshova, G. E., Zavodskaya Lab. 23, 1406 (1957); CA 54,8465 (1960). (133) Usatenko, Y. I., Shumskaya, A. I., Zavodskaya Lab. 26, 149 (1960); CA 54,11848 (1960). (134) Usatenko, Y. I., Tulyupa, F. Al., Zavodskaya Lab. 24, 1327 (1958); CA 54,13941 (1960). (135) Usatenko, Y. I., Tulyupa, F. LI., Zavodskaua Lab. 25. 280 11959): CA 54,18172”(1960). ‘ (136) Usatenko, Y. I., Tulyupa, F. &I., Zavodskaya Lab. 26, 783 (1960); CA 54,20666 (1960). (137) Usatenko, Y. I., Vitkina, &I. A., Zavodskaua Lab. 24. 1058 (1958): CA 54,15972 (1960). ‘ (138) Van Atta, R. E., Harrison, W. W., Sellers, D. E., ANAL.CHEX 32, 1548 (1960). (139) Vasilenko, V. D., Ukrain. Khim. Zhur. 26,767 (1960). (140) Vasil’ev, A. AI., Marunina, A. T., Trudy Kazan. Khim. Tekhnol. Inst im S.M. Kirova 1958, No. 22, 53; CA 53,17764 (1959). (141) Vinogradova, E. N., Gallal, Z. -1., Finogenova, Z. SI., “Methods of POlarography and Am erometric Analysis,” Izdatel. Moskov. 8niv., MOSCOW, 1960; CA 55, 6266 (1961). (142) Visvanathan, S., Sundararajan, K., Naravanan, U. H., Electrochem. Acta 2, 235 (1960). (143) Vladimirova, V. XI,,Trudy Komissii Anal. Khim., Akad. Nauk S.S.S.R., Inst. Geokhim. i Anal. Khim. 1 1 , 332 (1960); CA 55, 8153 (1961). (144) Weng, Y. K., Li, H. C., Yao Hsueh CA 54, 164 Hsueh Pao 7., 99 (1959): . (1960). (145) Williams, A. F., Brooks, J., Proc. Intern. Symposium Microchem., Birmingham Univ. 1958, 430 (pub. 1959). (146) Wilson, R. F., Baye, L. J., James, J., 2. anal. Chem. 171, 103 (1959,). (147) Yamamura, S. S., Rein, J. E., Booman. G. L.. ANAL.CHEM.31. 1868 (1959). (148) Yamashita, M., Nagoya Kogyo Gijutsu Shikensho Hokoku 5,334 (1956); CA 54,19279 (1960). (149) Yoshino, Y., Seno, A., Sugihara, hI., Yakuoaku Zasshi 80. 1484 (1960): CA . 55, 5g71 (1961). ‘ (150) Yu, H. Y., T’ao, T., Hua Hsueh Shih Chich 14, 300 (1959); C.4 54, 20670 (1960). (151) Zakharov, V. .4.,Songina, 0. A., Terzeman, L. N., Zavodskaya Lab. 26, 787 (1960); CA 54, 20656 (1960). (152) Zavarov, G. V., Zavodskaya Lab. 24,681 (1958); CA 54, 11818 (1960). (153) Zhdanov, A. K., Khadeev, V. A., Ishankhodzhaev, S. D., Uzbek Khim. Zhur. 1960, No. 3, 29; CA 55, 5237 (1961). (154) Zhdanov, A. K., Khadeev, V. A., Moiseeva, G. P., Zavodskaya Lab. 24, 137 (1958); CA 54,8421 (1960). (155) Zhdanov, A. K., Khadeev, V. A., Shamakhmudova, T. B., Zavodskaya Lab. 25, 1036 (1959); CA 54, 8452 (1960). (156) Zhdanov, A. K., Khadeev, V. A., Yakovenko. G. D., Zhur. Anal. Khim. 14, 367 (1959). ’ (157) Zobov, E. V., Lyalikov, Y. S., Mukhammednazarova. 0. M., Izvest. Akad. Nauk Turkmen. S.S.R. 1959, No. 4, 45; CA 54,6409 (1960). (158) Zolotavin, V. L., Ponomareva, L. K., Redkozemel’nye Elementy (Poluchenie, Analiz, Primenenie) 1959, 176; CA 55,20770 (1961). ‘

. I