Titrations in Nonaqueous Solvents

Titrations in Nonaqueous Solvents. C. A. Streuli, American Cyanamid Co., Stamford, Conn. The interest in nonaqueous solvents as media for acid-base ti...
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Review of Fundamental Developments in Analysis

Titrations in Nonaqueous Solvents C. A. Sfreuli, American Cyanamid Co., Stamford, Conn.

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interest in nonaqueous solvents as media for acid-base titrations has continued during the past two years. There has been increased information on the varying properties of solvents, on solute-solvent interactions, and on the use of photometric, thermometric, and high frequency techniques as well as the more standard potentiometric and conductometric methods. Redox reactions have achieved some prominence, and Lewis acids as titrants also appear more popular. ii number of procedures have been adapted to the micro level through both standard titrations and coulometric approaches. The review presented here covers papers which have been published in the interval between the last review by Riddick (98)and late September of 1961. Some papers published in this interval have been excluded when it was felt that they did not add appreciably to the present body of knowledge in this area. HE

GENERAL ACID-BASE STUDIES

Hoover and Hutchinson (46) have studied the conductance of water, acetic anhydride, and acetyl chloride in acetic acid at 25°C. They found that both water and the anhydride are extremely weak electrolytes in this system, while acetyl chloride is more dissociated. Bruckenstein (IO) has discussed the acidity function in glacial acetic acid. He has considered the effect of small concentrations of water in the solvent on this function and given a quantitative description of its influence. Kenttamaa and Heinonen (54) have shown that the ratio of the dissociation constant of a base to that of its salt in anhydrous acetic acid can be calculated from the slope of the titration curve. Their equations are based on equations derived by Kolthoff and Bruckenstein. The indicator method developed by Kolthoff and Bruckenstein for glacial acetic acid has been applied by Hummelstedt and Hume (48) to acid-base reactions in o-dichlorobenzene, chlorobenzene, and benzene, as well as a mixture of o-dichlorobenzene and acetonitrile. The experimental data indicate that the application of this method to nonacidic solvents of low dielectric constant is made impossible by a variety of complicating association reactions. These include 302 R

ANALYTICAL CHEMISTRY

both multiple ion formation and solvation of the indicator salt by the acid used. Finally, protonated and unprotonated indicator species appear to associate in benzene. Flowers, Gillespie, and Robinson and their collaborators have studied sulfuric acid as a solvent for acid-base reactions (26). They have determined the autoprotolysis of this acid a t loo, 25", and 40°C. and obtained values of 1.7, 2.4, and 3.2 X respectively (35). They also studied the conductivities of metal sulfates, ketones, and tetra(hydr0gen sulfato) boric acid in this acid ( 2 ) . A variety of conductivity studies have been made by others using a number of nonaqueous solvents. Among these is the work of Brewster, Schmidt, and Schaap (8),who measured conductance of alkali metals, halides, nitrates, and nitrites in anhydrous ethanolamine. They found the conductance of the halides in the reverse order of that observed in dimethylformamide and N-methylacetamide. The conductance of lithium ion in methylamine at - 78.3"C. was studied by Berns, Evers, and Frank (7), while Evers and Frank (23) measured the conductance properties of sodium in liquid ammonia. They proposed a conductance function which represents experimental data for solutions up to 0.04N of sodium in this solvent. The function takes into account such species as the solvated electron, solvated metal ion, ion pair, and dimer. Sverage differences between observed and calculated values for A were 0.9%. Fuoss and Hirsch (33) measured the conductance of tetr'abutylammonium tetraphenylboride in sei-era1 nonaqueous solvents; Emeleus and Harris ($1) shon-ed that while dichlorotris(trifluoromethy1)phosphorane is ionized in acetonitrile the trichlorobis derivative is not. They also studied conductivity titrations of these compounds with bromine. The electrical conductance and dissociation constants of ion pairs formed by proton transfers to conjugate polymers are the subject of a paper by Wasserman (118). He shows a linear logarithmic relation between molar conductance and the concentrations of ion pairs formed in benzene solution using polymers such as 0-carotene and a proton donor such as trichloroacetic acid. Other conductance studies in solvents

of low dielectric strength have been made by Hirsch and Francis (M),using tetrabutylammonium salts in nitrobenzene-carbon tetrachloride mixtures covering the dielectric range of 5 to 35, and French and Hart (28)) who also used tetraalkylammonium salts as solutes and triethyl phosphite as the solvent. They account for their results on the basis of extensive ion pairs and triple ion formation. The use of lithium chloride in nonaqueous potentiometric titrations was studied by Grove (38). Its real usefulness was found to be in the titration of Keak acids with sodium methoxide in neutral or weakly basic solvents. In the titration of benzoic acid in dimethylformamide the lithium chloride improved the p H meter stability and caused an increase in Ac/AV ratio a t the end point. In titrations in acetic acid or chlorobenzene the salt is undesirable. hfarkowitz et al. (73) have published a n extensive list of the solubility of lithium perchlorate in over 50 organic solvents, which include esters, amines, ethers, nitriles, and ketones as well as acids and alcohols. Pro11 and Sutcliffe (96) have determined the dissociation constants of eleven inorganic acetates in anhydrous acetic acid. These include the principal alkali and alkaline earth acetates. Streuli (109) has shown that in nitromethane ureas and some amides increase their basicity relative to amines. The effect is ascribed to solvation. In another paper this author (110) showed that phenols and other noncarboxylic acids when titrated in pyridine increase their apparent acidity relative to carboxylic acid. An equation relating acidity of phenols in pyridine and in irater is presented. Forman and Hume (27) have determined the heats of neutralization of 32 amines in acetonitrile using perchloric acid and the thermometric titration technique. The heats of neutralization are shown to be a good relative measure of base strength in this sollent for aromatic, primary aliphatic, and straightchain secondary amines. Correlation of AH values for aliphatic amines with Z U * is attempted. In other studies of basicity Hinman and Lang (43) have discussed the position of protonation and the basicity of indoles, while Martin and Reece (74)

have studied the effect of increasing methylation on the basicity of aliphatic amides in glacial acetic acid. I n compounds of the type CHaCONHR basicity increases with increasing methylation; for the type RCONH2basicity decreases with increasing methylation. Streuli (111) determined the basicities of over 30 substituted phosphines in nitromethane using potentiometric titration techniques. These values have been extrapolated to pK, (H20) values. The determination of a number of other constants is of interest to the nonaqueous acid-base field. Newall and Eastham (88)have redetermined the relative basicities of water, methanol, and ethanol using a kinetic approach. deLigny and his collaborators in a series of papers (64-67) have considered pH effects, liquid junction potentials, and the dissociation constants of some aliphatic amines in methanol and methanol-water mixtures. deLigny and Rieneke (68) also determined the value for the standard potential of the silversilver bromide electrode in anhydrous methanol a t 25' C. Moodie (85)lists the relative Lewis base strength of substituted acetophenones at 21" C. for reaction with boron trifluoride in diethyl ether. Bates and Hetzer (3) have made a careful determination of the thermodynamic dissociation constant of the protonated form of 2-amino-2-(hydroxymethyl)-l,3propanediol ("tris") from 0" to 50" C. The compound has been previously proposed as an analytical standard. The pK, a t 25" C. is 8.075. They also list comparable values for 18 other cationic acids plus other thermodynamic data. TITRANTS, SOLVENTS, AND INDICATORS

Caso and Cefola (12) have studied methane-, ethane-, benzene-, and naphthalenesulfonic acids as titrants using a potentiometric technique, acetic acid as the solvent, and potassium hydrogen phthalate as the primary standard. Although maximum Ae/AV values are only about tn-o fifths of those obtained using perchloric acid, precipitates and gels are not formed when the sulfonic acids are used. Precision was 0.2 to 0.5%. A visual end point with crystal Lriolet could also be obtained. Cnso and Cefola ( 11 ) also studied the standardization of lithium methoxide against sulfamic acid using dimethylformamide, dimethyl sulfoxide, n-butylamine, and ethylenediamine as solvents. Both visual and potentiometric methods were used. The solvents might contain up to 2% water without effect. Precision ranged from 0.27 to 0.5%. Kreshkov, Bikova, and Mchitarjan (58) proposed tetraethylammonium hydroxide as a titrant in methyl ethyl ketone for the titration of weak and very weak acids. Fijolka and Lena (25)

used butyl triethylammonium hydroxide for the titration of weak acids. However, they found that 0.01N solutions of this reagent are unstable. Ting, Jeffery, and Grove (114) compared five alkali metal methoxides for use as titrants of acids in dimethylformamide using high frequency methods. Although the methoxides of cesium and rubidium are the strongest bases, the difference in these values from those for the sodium and potassium derivatives is not sufficient to justify their preferred use. Lithium methoxide acts as a very weak base in the solvent system used but sloivly dissociates with increasing concentrations of methanol. There is evidence of slight reaction of the methylate ion with dimethylformamide. Zuffanti, Oliver, and Luder (120)&-ere able to form complexes between borate esters and sodium methoxide in methanol. The Lewis acid properties of the borate esters were also studied in benzonitrile. Kolling and Smith (55) examined several p-aminophenyl derivatives of the triphenylmethane series of dyes for use in nonaqueous titrations. -4 number were found acceptable for titration of strong and intermediate bases with perchloric acid. Kolling and Stevens (56)also proposed a number of new indicators for titrations in acetic acid. TECHNIQUE

Humnielstedt and Hume have made two extensive investigations of the photometric titration of weak acids (47) and weak bases (49) in nonaqueous solvents. The acids and solrent were phenols in isopropyl alcohol, the titrant tetrabutylammonium hydroxide in isopropyl alcohol. A list of appropriate wavelengths is given for 16 phenols; up to four components of a mixture can be resolved in favorable cases by making wavelength shifts after each break in the curve of extinction us. volume of titrant. The same considerations are emphasized for the determination of weak bases in either acetic acid or acetonitrile. Perchloric acid is the titrant in this case, Van Meum and Dahmen (77,78)have used the conductometric and potentiometric techniques to study similar acids and bases. For nitrogen bases they recommend alcohol-benzene and nitrobenzene-xylene solvent systems. For dibasic compounds they show that the slope of the titration curve depends on distance between groups, solvent, temperature, and acid anion. The paper on the titration of acids (78) utilizes the conductometric technique exclusively. In general, 0.1 to 0.3N tetrabutylammonium hydroxide is the preferred titrant and pyridine the most favorable solvent. Mixtures of dimethylformamide and benzene, 1 to 3, are also useful.

Reynolds, Kalker, and Cochran (96) have titrated amines directly in pyridine with acetic anhydride using a spectrophotometric technique. Precision is within 0.8%. Photometric indicator titrations were also carried out by Connors and Higuchi (16) for compounds such as acetamide, urea, and caffeine. Results were obtained using the modified Type I1 plot. Karsten, Kies, and de Hoog ( 5 3 ) have used Higuchi's technique t o determint. quantities of base of the order of 1 meq. If the water content of the solvent (acetic acid) is high, results are less reliable. In the high frequency titrations of organic bases in nonaqueous solvents Riolo and Kotarianni (99) have shown that higher acidity of the solvent improves localization of the end point of medium and high strength bnses, while it makes determination of very weak bases impossible. Grove and Jeffery ($9) in studying the suitability of organic solvents for high frequency titration of weak acids conclude that solrents of low basicity and high dielectric strength are best for titrations using this technique. Fripiat, Vancompernolle, and Servais (SO) have described a titrator for high frequency titration of acidic solids. Theoretical relations for the Hammett function and the acidity of the solids are also given. Mullen and Anton (86) have described a photometric titrator employing commercially available instruments used in combination. It appears very versatile. Jordan and his collaborators (51, 52) have continued work with thermometric titrations. His two most recent papers deal with titration of chlorides in fused potassium nitrate a t 158" c. Silver nitrate in the same fused solvent was the titrant. Shain and Svoboda (105) utilize two polarized platinum electrodes which pass a small constant current (1 pa.) for the titration of weak acids in acetone. Peak-shaped titration curves are obtained; differentiation of acids can be accomplished. Siggia and Hanna (106) used acetylation rate studies to determine two-component mixtures. The rate reactions were followed by titrations. The method was applied to mixtures of isomeric, primary, and secondary alcohols. METHODS

A number of men have adapted nonaqueous acid-base titrations to the micro scale. Gutterson and Ma (41) have obtained satisfactory results using both acetic acid and acetic anhydride as solvents, 0.01N solut,ions of perchloric acid and suitable indicators. Sample sizes were 3 to 5 mg. Belcher, Berger, and West (6) obtained satisfactory titrations on the submicro scale (0.03 to 0.05 ml. VOL. 34, NO. 5, APRIL 1962

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of titrant required). Alicino (1) titrated 3- to 5-mg. samples of thiourea using a mercuric acetate reagent and 0.01N standard acid. Lohr (69) has used standard solution of cyclohexylamine for the direct titration of acid chlorides in tetrahydrofuran or glyme. There is no interference by carboxylic acids, but hydrochloric acid will invalidate results. Stuck (112) was able to differentiate sulfuric from hydrochloric acid in methanol by titrating with a standard solution of cyclohexylamine. Results for mixtures of sulfuric n-ith sulfonic, nitric, and phosphoric acids are also given. Fritz and Palmer (32) have utilized mercuric perchlorate as the titrant for the visual or potentiometric determination of mercaptan. Smaller quantities of thiols in hydrocarbon solution are titrated photometrically. Bayer and Posgay (5) have used a combination of mercuric acetate reagent and standard perchloric acid solution in acetic acid for visual titration of compounds containing -SH or =S groups. Kreshkov, Drozdov, and Jlasova in a series of papers (59-6a) have described the titration of organosilicon compounds containing nitrogen and carboxyl functions with standard acid or bases using acetonitrile or nitromethane in combination with benzene or dioxane as the solvents (61, 62). Methylchlorosilanes may be differentiated by conductometric titration in acetonitrileethyl ether. The compounds are first converted to the alkylthiocyanate derivatives by the action of ammonium thiocyanate. Amidopyrene is the titrant (59,60), Sulfonates and phenoxides of calcium and barium used as detergent additives in lubricating oils can be determined by titration in ethanol-benzene mixtures with a standard solution of a strong acid in the same solvent, according to Larbre and Briant (63). I t is possible to distinguish between the two metallic ions. Goldstein, hlenis, and Manning (37) titrated sulfate indirectly by precipitating the anion in aqueous solution with excess barium acetate, added acetic anhydride to convert the solvent to acetic acid, and then back-titrated the excess barium salt with standard perchloric acid. Interference by some anions and cations is encountered. Schenk and Fritz (103) and Schenk (102) have utilized their rapid acetylation procedure which employs perchloric acid as a catalyst for the determination of phenols, thiols, and amines (103) and aldoximes and ketoximes (102). Sterically hindered phenols can be titrated after reaction for only 5 minutes a t room temperature. The acetylation reaction is more rapid in ethyl acetate than in pyridine. 304 R

ANALYTICAL CHEMISTRY

Robinson, Cundiff, and hlarkunas (100, 101) have s h o m that the reaction

product of alcohols or symmetrical ethers with 3,5-dinitrobenzoyl chloride can be titrated in pyridine with tetrabutylammonium hydroxide using either visual or potentiometric methods. Polyols, sugars, phenols, primary and secondary amines, and some oximes may also be determined. Cundiff and Markunas (17) have also determined alkoxy1 groups by forming the iodide, distilling this product into pyridine, and titrating with tetrabutylammonium hydroxide. Hydriodic acid, iodine, and sulfide do not interfere. The titration may be followed visually or potentiometrically. A direct spectrophotometric titration of water in acetic acid in the range 0.009 to 1.7% has been described by Bruckenstein (9). Acetic anhydride is the titrant, sulfuric acid the catalyst. Takahashi and Robinson (113) have titrated copper and nickel nitrates in dimethylformamide spectrophotometrically u-ith 1-nitroso-2-naphthol. The titrant is not highly stable in this solvent. Malone (71) was able to differentiate between hydrazine and 1,l-dimethylhydrazine by treatment with salicylaldehyde and subsequent titration with perchloric acid, Although both original compounds are basic, hydrazine forms a neutral product with the aldehyde. The product of the substituted hydrazine and aldehyde is, however, basic. Sodium citrate and sodium potassium tartrate were assayed by Richardson (97) by titration in acetic acid with perchloric acid. A back-titration method was used for the tartrate. Smith and Haglund (108) have described the titration of 27 phenolic esters in acetone with tetraalkylammonium bases. The mechanism of the reaction is discussed briefly together with some exceptions to the general rule. A certain number of papers have also appeared on the titration of alkaloids and pharmaceuticals. These include visual titration of codeine, morphine, narcotine, and papaverine (116) in acetic acid, and the salts of the alkaloids by a photometric technique (4). Ellert, Jasinski, and Pawelczak (20) have used propionic acid-propionic anhydride as the solvent medium for the visual titration of phenazone, caffeine, and theophylline with perchloric acid. Results using a number of indicators are given. Ellert, Jasinski, and Marcinkoivska (19) also describe photometric titration of benzocaine, adrenaline, phenazone, caffeine, narceine, sulfanilamide, sulfathiazole, sulfapyridine, and quinine sulfate in acetic acid with perchloric acid. Titration of isoniazid, sulfafurazole, and the salts of phenothiazine bases has also been reported by Mizukami and Hirai (81, 82) .

SOLVENT PURIFICATION

Two short papers on solvent purifications have been published recently. To remove basic impurities from nitromethane Clarke and Sandler (14) passed the solvent through a sulfonic acid exchange resin which had previously been dehydrated with methanol. LIoskalyk, Chatten, and Pernarowski (84) removed acidic impurities from dimethylformamide by shaking the solvent with a strongly basic resin for several hours, then filtering. I n both cases the authors mention a considerable decrease in the blank titration. LEWIS ACIDS

The use of tetracyanoethylene as a Lewis acid titrant has been exploited by Ozolins and Schenk for the titration of both aromatic hydrocarbons and dienes. Anthracene in naphthalene (104) may be determined by photometric measurement of the lowering of the extinction of a chloroform solution containing the naphthalene-cyanoethylene complex, since the anthracene complex is more stable. Benzene and toluene do not interfere but indene, phenanthrene, chrysene, and other hydrocarbons do to some extent. The same authors also describe the determination of dienes with this reagent (90) by adding an excess of the reagent to the dienes and back-titrating with A visual titration cyclopentadiene. with indicators and a direct photometric titration are described. Clark, Balloy, and Barth (13) have described a direct potentiometric titration of solid catalysts slurried in acetonitrile with butylamine. A glass-calome1 electrode combination is used. The authors relate the height of the potential break with the acidity of the catalyst, and the length of the titration as a quantitative measure of surface acidity. Stannic and titanium tetrachlorides have been used by Paul, Singh, and Sandhu (91) for the titration of heterocyclic and tertiary amine bases. Benzanthrone was used as the visual indicator for this work. Useful results were obtained in the solvents phosphorus oxychloride, sulfonyl chloride, and thionyl chloride but not in arsenic trichloride, carbon tetrachloride, or chlorobenzene. The authors explain the difference in behavior of the indicator on the basis of polar and nonpolar solvents. Emeleus and hlacKay (22) have carried out conductometric titrations of sodium in liquid ammonia with phosphine, arsine, and stibine. The conductivity is decreased as the monoand disodium salts of the hydrides are formed. They also n-orked with a number of germanes.

The conductivity of antimony trichloride and cesium chloride in acetic acid has been studied by HaGii: (42). Cesium chloride may be titrated with antimony trichloride in this medium. Manhas, Paul, and Sandhu (72) have performed conductometric titrations in acetyl chloride using titanium and stannic tetrachloride as acids and quaternary ammonium chlorides as well as heterocyclic nitrogen compounds as bases. The hydrochloric acid complex of chloroaluminum isopropoxide has been used by Simonyi and Tokar (107) as a titrant for alkaloids. The reagent acts as a monobasic acid; titrations are carried out in chloroform. The same authors have also used the same reagent for the determination of aniline, p-anisidine, p-phenetidine, and the esters of p-aminobenzoic acid in the same solvent (115). Potentiometric and high frequency titrations in acetone and acetic acid for the determination of trace quantities of chlorides and mercaptans are the subject of a paper by van AIeurs (79). The titrant is 0.001N silver nitrate in isopropyl alcohol or acetone. The author claims 0.05-pmole deviations for samples of 0.5 to 10 pmoles. He also maintains the electrode response is sufficiently rapid in this solvent, so that automatic titration may be used. For the high frequency titration a frequency of 11 me. per second is recommended. Nadeau, Oaks, and Buxton (87) have determined chlorine bound to boron as organic compounds using methanolic solutions and standard silver nitrate solutions. Murakami (86) has determined sulfuric acid (1%) in acetylating mixtures by titrating with lead or barium acetate in glacial acetic acid. Crystal violet is used as a n indicator. Water obscures the end point but may be eliminated by the addition of acetic anhydride. Guerrin, Sheldon, and Reilley (40) have published procedures for the titration of a variety of metal ions in dimethylformamide with EDTA. An indicator, SNAZOXS [8-hydroxy7 - ( 4 - sulfo - 1 - napthy1azo)quinoline5-sulfonic acid], is used. Back-titrations, when employed, use C U + ~ solutions. Iron and aluminum can be determined in the presence of each other. COULOMETRY

Perhaps the most interesting development in coulometry in nonaqueous solvents has been the generation of hydrogen ions in a n acetic acid-acet,ic anhydride mixture, reported by Mather and Anson (76). The hydrogen ion generation is accomplished by the anodic oxidation of mercury which reacts with the acetic acid to give insoluble mercurous acetate and hydrogen ion [2Hg PCH3COIH = Hgz(02CCH3)e 2 H +

+

+ +

2e-1. Quantitative titrations of potassium hydrogen phthalate and sodium acetate were accomplished. The titration may be followed with a glass electrode and a mercury-mercurous acetate reference electrode. Sodium perchlorate, O . l M , is the supporting electrolyte. The technique is applicable to the titration of microgram quantities of base except easily acetylated amines. This same method has been applied by these authors (75) to the determination of fluoride. For fluorides alone (1.5 mg.) the method is accurate within 0.2%. Most anions interfere. Chloride-fluoride mixtures may be resolved. Coulson and Cavanagh (16) have described a n automatic halide analyzer which utilizes acetic acid as the principal solvent medium for the analysis. Olson (89) has used a methanol-acetic acid mater system and coulometrically generated bromine for the determination of hydrazine and substituted hydrazines. Mercuric acetate and potassium bromide are used and the reaction is follotved amperometrically with a platinum \Tire indicating electrode. Samples of 3 to 5 mg. of a substituted hydrazine gave a coefficient of variation of 0.8%. REDOX REACTIONS

A study of iodometry in acetonitrile has been made by Desbarres (18). He has determined the stability constant of 1 3 - in this system and the normal potentials of the redox systems Ia-/I- and I&-. The possibilities of using this system for potentiometric titrations are discussed. Fauth and McNerney (24)have used iodate-iodide for the determination of decaborane in glacial acetic acid. A standard deviation of 0.37 is reported for 10 determinations on a sample assaying a t 98%. Mader, Schoenemann, and Eye (7‘0)have determined nonaromatic unsaturates in automobile exhausts by spectrophotometric titration using standard bromate-bromide solutions. The’olefins (C4 and higher) are collected in carbon tetrachloride diluted in acetic acid and methanol and then titrated. The method is applicable to olefins in the 25- to 1000-p.p.m. range. The use of ceric ammonium nitrate for the oxidation of xanthates, iodide, and hydroquinone in acetonitrile has been studied by Rao and Murthy (93, 94). A platinum indicating electrode was used in combination with either a glass or an antimony electrode as the reference electrode. Giuffre and Capizzi (36) determined the sum of Ti+2 and Ti+3 by oxidation with standard ferric chloride in anhydrous methanol. An inert atmosphere is necessary. Titrations were run a t -15’ to 0” C. Minczewskiand Kolyga (80) used a solution of chromous acetate

in dioxane for the potentiometric titration of uranyl salts. A nitrogen atmosphere was maintained. Hubicki and Wiacek (46) used trimethylamine in glacial acetic acid as the solvent for the potentiometric titration of a variety of compounds which included thallium acetate with iodide, stannous chloride with dichromate, and hydrazine with periodate. REVIEWS

General review on the subject of acid-base titrations in nonaqueous solvents include those of Fritz (SI), Gautier (Sd), and Isniailov (50). Frind and Busch (29) have discussed the use of the glass electrode as the indicator electrode for nonaqueous acid-base titrations. Veibel(117) reviews methods for the determination of carboxylic acids, anhydrides, and esters. TKO new books, “Comprehensive Analytical Chemistry,” edited by Wilson and Kilson (119), and “Advances in Analytical Chemistry,”edited by Reilley (95) with a chapter by Flaschka, contain material on titration in nonaqueous media. Lastly the “Treatise on Analytical Chemistry,” edited by Kolthoff and Elving (57), has an excellent section on acid-base chemistry in general and a separate chapter dealing with acid-base equilibria in nonaqueous solvents written by Kolthoff and Bruckenstein. LITERATURE CITED

(1) Alicino, J. F., Microchem. J. 4, 561 (1960). (2) Bass, S. J., Flowers, R. H., Gillespie,

R. J., Robinson, E. A., Solomons, C., J. Chem. SOC.1960,4315. (3) Bates, R. G., Hetzer, H. B., J. Phys. Chem. 65, 667 (1961). (4) Bayer, I., Pharm. Zentralh. 100, 6

(1961). (51 Bayer, I., Posgay, E., Ibid., 100, 65 (1961). (6) Belcher, R., Berger, J., West, T. S., J. Chem. SOC.1959,2877. (7) Berns, D. A., Evers, E. C., Frank, P. W., J. Am. Chem. SOC.82,310 (1960).

(8) Brewster, P. W., Schmidt, F. C., Schaap, W. G., Ibid., 81, 5532 (1959).

(9) Bruckenstein, S., ANAL. CHEM. 31, 1757 (1959). (10) Bruckenstein, S., J. Am. Chem. Sac. 82,307 (1960). (11) Caso, M. hl., Cefola, hi., Anal. Chim. Acta 21. 205 (1959). (12) Ibid., p. 374.

(14) Clark. R. 0., Balloy, E. V., Barth, R. T.. 16id.. 23. 189 (1960). (14) Clarke, G., Sandler, ’ S., Chemist Analyst 50, 76 (1961). (15) Connors, K. A., Higuchi, T., ANAL. CHEM.32, 93 (1960). (16) .Coulson, D. M., Cavanagh, L. A., Ibzd., 32, 1245 (1960). (17) Cundiff, R. H., Markunas, P. C., Ibid., 33, 1028 (1961). (18) Desbarres, J., Bull. sac. chim. France 1961, 502. (19) Ellert, H., Jasinski, T., Marcinkowska, K., Acta Polon. Pharm. 17, 29 (1960). (20) Ellert, H., Jasinski, T., Pawelczak, I., Ibid., 16, 235 (1959).

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(21) Emeleus, H. J., Harris, G. S., J . Chem. SOC.1959, 1494. (22) Emeleus, H. J., MacKay, K. M., Ibid., 1961, 2666. (23) Evers, E. C., Frank, P. W.,J . Chem. Phys. 30, 61 (1959). (24) Fauth, M. I., McNerney, C. F., ANAL.CHEM.32, 91 (1960). (25) Fijoka, P., Lenz, I., Plaste u. Kautschuk 7, 169 (1960). (26) Flowers, R. H., Gillespie, R. J., Robinson, E. A., Can. J . Chem. 38, 11960). 1363 ~ . . \ - -~ --,(27) Forman, E. J., Hume, D. N., J . Phys. Chem. 63, 1949 (1959). (28) French, C. M.,Hart, P. B., J . Chem. SOC.1960,’ 3161. (29) Frind, H., Busch, A., Chemiker-Ztg. 84. 568 11960). (30) ‘Fripiat, J.’ J., I7ancompernolle, G., Servais, A., Bull. SOC. chim. France 1960, 250. (31) Fritz, J. S., Record Chem. Progr. (Kresge-Hooker Sci. Lib.) 21, 95 (1960). (32) Fritz. Fritz, J. S.. S., Palmer. Palmer, T. A, ’4..ANAL. CHEM.33. is61 1. ’ 33, 98 f(1961). (33) FUOSS, R. hf., Hirsch, E., J . Am. Chem. SOC.82, 1013 (1960). (34) Gautier, J. A., Bull. soc. chim. France 1959, 279. (351 Gi llespie R. J., Robinson, E. A., J. Chem. SOC.1960, 4320. golomons, 6., (36) ,Giuffre, L., Capizzi, F. M., Ann. chzm. (Rome) 50, 1150 (1960). (37) Goldstein, G., Menis, O., Manning, D. L., ANAL. CHEM.33, 266 (1961). (38) Grove, E. L., Talanta 4, 205 (1960). (39) Grove, E. L., Jeffery, W. S., Ibid., 7. 56 f19601. (40) Guerrin,’G., Sheldon, M. V., Reilley, C. N., Chemist Analyst 49, 36 (1960). (41) ,Gutterson, M., Ma, T. S., Mikrocham. Acta 1, 1 (1960). (42) HaGiE, J., Collection Czechoslov. Chem. Communs. 25. 695 f 1960). (43) Hinman, R. L., Lang,’J., Tetrahedron Letters 2 1, 14 (1960). (44) Hirsch, E., Francis, R. M., J . Am. Chem. SOC.82, 1018 (1960). (45) Hoover, T. B., Hutchinson, A. W., Zbid., 83, 3400 (1961). (46) Hubicki, W-.,Wiacek, R., Z. anal. Chem. 175, 97 (1960). (47) Hummelstedt, L. E. I., Hume, D. N., AISAL.CHEM.32, 1792 (1960). (48) Hummelstedt, L. E. I., Hume, D. N., J . Am. Chem. SOC.83, 1564 (1961). (49) Hummelstedt, L. E. I., Hume, D. N., U. S. At. Energy Comm., Rept. AECU4561 (1959). (50) Ismailov, X. A., Zavodskaya Lab. 26,29 (1960). (51) Jordan, J., Meier, J., Billingham, E. J., Jr., Pendergrast, J., ANAL. CHEW31, 1439 (1959). (52) Zbid., 32, 651 (1960). (53) Karsten, P., Kies, H. L., de Hoog, P., Rec. trav. chim. 79, 610 (1960). (54) Kenttamaa, J., Heinonen, E., Suomen Iiemistilehti B32, 189 (1959). ’

~

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(55) Kolling, 0. W.,Smith, M. L., AISAL. CHEW31, 1876 (1959). (56) Kolling, 0. W.,Stevens, T. L., Ibid., 33, 1384 (1961). (57) Kolthoff, I. M., Elving, P. J;: “Treatise on Analytical Chemistry, Part I, Vol. I, pp. 405-16, 475-540, Interscience, New York, 1959. (58) Kreshkov, A. P., Bikova, L. N., Mchitarjan, N. A., Doklady Akad. Nauk S.S.S.R. 132, 1090 (1960). (59) Kreshkov, A. P., Drozdov, V. A., Zbid., 131, 1345 (1960). (60) Kreshkov, A. P., Drozdov, V. A., Vlasova, E. G., Izvest. Vysshikh Ucheb. Zavedenzi, Khzm. i Khim. Tekhnol. 3, 80 (1960). (61) Zbid., p. 85. (622 Kreshkov, A. P., Drozdov, 1’. il., klasova, E. G., Zavodskaya Lab. 26, 1080 (1960). (63) Larbre, J., Briant, J., Rev. inst. franc. pdtrole 15, 1170 (1960). (64) Ligny, C. L. de, Rec. trav. chim. 79, 731 (1960). (65) Ligny, C. L. de, Luykx, P. F. M., Rehbach, M., Wieneke, A. A., Zbid., 79, 699 (1960). (66) Ibid.. n 719 (67j Ligni 79.

(68) ‘1

Ibid.,-79, 261 (69) Lohr, L. (1960). (70) Mader, P. P., Schoenemann, K., Eye, M., Zbid., 33,733 (1961). (71) Malone, H. E., Zbid., 33, 575 (1961). (72) Manhas, D. S., Paul, R. C., Sandhu, S . S., J . Chem. SOC.1959,325. (73) Markowitz, M. M., Hawley, W. N., Boryta, D. A., Harris, R. F., J . Chem. Eng. Data 6 , 325 (1961). (74) Martin, R. J. L., Reece, I. H., J . Chem. SOC.1960, 4697. (75) Mather, W. B., Anson, F. C., ANAL. CHEM.33, 132 (1961). (76) Mather, W. B., Anson, F. C., Anal. Chim. Acta 21, 468 (1959). (77) Meurs, N. van, Dahmen, E. A., Ibid., 21, 193 (1959). (78) Ibid., p. 443. (79) Meurs, N. van, J . Electroanal. Chem. 2, 17 (1961). (80) Minczewski, J., Kolyga, S., Chem. Anal., Warsaw 3, 463 (1958). (81) Mizukami, S., Hirai, E., J . Pharm. SOC.Japan 79, 454 (1959). (82) Ibid., p. 457. (83) Moodie, R. B., Chem. & Ind. (London) 32, 1269 (1961). (84) Moskalyk, R. E., Chatten, L. G., Pernarowski, M., J . Pharm. Sci. 50, 179 f 1961). (85) biullen, P. W., Anton, A., ANAL. CHEM.32, 103 (1960). (86) Murakami, T., Japan Analyst 8, 103 (1959). (87) Kadeau, H. G., Oaks, D. M., Buxton, R. D., ANAL.CHEM.33,341 (1961).

(88) Sewall, C. E., Eastham, A. I I . , Can. J . Chem. 39, 1752 (1961).

(89) Olson, E. c., -4N.4L. CHEM.32, 1545 (1960). (90) Ozolins, M., Schenk, G. H., Ibzd., 33, 1035 (1961). (91) Paul, R. C., Singh, J., Sandhu, S. S., Zbid., 31, 1495 (1959). (92) Proll, P. J., Sutcliffe, L. H., Trans. Faraday SOC.57, 1078 (1961). (93) Rao, G. P., Murthy, A. R. V., Z. anal. Chem. 177, 86 (1960). (94) Ibid., 182, 358 (1961). (95) Reilley, C. ,N., “Advances in Analytical Chemistry and Instrumentation,” Vol. I, pp. 96-8, Interscience, Xew York. 1960. (96) Reynolds, C. A., Walker, F. H., Cochran, E., ANAL. CHEW 32, 983 (1960). (97) Richardson, M. L., Anal. Chim. Acta 24,46 (1961). (98) Riddick, J. A., ANAL. CHEM. 32, 172 R f 1960). (99) Riolo, C.B., Kotarianni, A. F., Ann. chim. (Rome)49, 1981 (1959). (100) Robinson, W. T., Jr., Cundiff, R. H., Markunas, P. C , ANAL.CHEM.33. 1031 (1961). (101) Robinson, IT. T., Jr., Cundiff, R. H., Sensabaugh, A. J., Markunaa, P. C., Talanta 3, 307 (1960). (102) Schenk, G. H., A N ~ LCHEM. . 33,299 (1961). (103) Schenk, G. H., Fritz, J. S., Ibid., 32, 987 (1960). (104) Schenk, G. H., Ozolins, X, Talanta 8, 109 (1961). (105) Shain, I., Svoboda, G. R., Ax.4~. CHEW31, 1857 (1959). (106) Siggia, S., Hanna, J. G., Ibid., 33, 897 (1961). (107) Simonyi, I., Tokar, G., Acta Chim. h a d . Sci. Hung. 25, 305 (1960). (108) Smith, B., Haglund, A., dcta Chem. Scand. 14, 1349 (1960). (109) Streuli, C. A,, ANAL. CHEM. 31, 1653 (1959). (110) Zbid., 32, 407 (1960). (111) Ibid., p. 985. (112) Stuck, W., Z anal. Chem. 177, 338 (1960). (113) Takahashi, I. T., Robinson, R. X., AISAL.CHEM.32, 1350 (1960). (114) Ting, S. F., Jeffery, W. S., Grove, E. L., Talanta 3, 240 (1960). (115) Tokar, G., Simonyi, I., Acta Chim. Acad. Sci. Hung. 25,313 (1960). (116) Tuthill, S. hf., Kolling, 0. W., Roberts, K. H., ANAL.CHEX.32, 1678 (1960). (117) Veibel, S., Chim. anal. 41,49 (1959). (118) Wasserman, il.,J . Chem. SOC.1959, 986. (119) Wilson, C. L., Wilson, D. IT., “Comprehensive Analytical Chemistry,” Vol. IB, Van Nostrand, Princeton, N. J., 1960. (120) Zuffanti, S.,Oliver, R. J., Luder, W.F., J . Phys. Chem. 63, 1537 (1959).