ANALYTICAL CHEMISTRY
360 manganese; and nickel plus zinc migrated away from the cobalt ions, the nickel moving slightly faster than the zinc. With ammonia plus 2% triethanolamne as electrolyte, zinc migrated dower than nickel, and cobalt migrated slightly toward the anode. Use of this solvent for three-way development of a strip cut from the two-way chromatogram improved the separation of cobalt, manganese, zinc, and nickel. Subgroups of theiron and aluminum family were readily separable by one-way electrolysis. In addition t o the separation of ferric, aluminum, chromic, and chromate ions, ferric and manganous ions and aluminum, zinc, and chromate ions were also separated in lactic acid. Aluminum, zinc, and chromate ions were separated in lactic acid, in 2% triethanolamine plus 4 iM ammonia, and in 4 M ammonia. In triethanolamine (2%).plus triethylamine (2%) both aluminum and zinc were weakly anionic. Cobalt and nickel were separated in 4 M ammonia, in 4 M ammonia plus 2% triethanolamine, and in triethanolamine (2%) plus triethylamine (2%) (Table V). Ions of several groups exhibited the electrical migration behavior summarized in Table V. In the presence of complexforming agents, many cations exhibited anionic properties, and with different reagents, various ions of the mixtures could be made the leading electrochromatographic zones. These results indicate that various solvents may be utilized to effect a complete separation of particular components from mixtures. Thus with triethanolamine plus triethylamine, copper and cobalt may be separated completely from nickel or silver; with trimethylamine-cu,cu’,a”-tricarbo~ylic acid, copper and nickel may be separated completely from cobalt and silver; with ammonia plue triethanolamine, cobalt may be separated completely from copper, nickel, and silver; with triethanolamine plus glutamic acid, copper, cobalt, and nickel may be prepared free of silver. As each ion formed a single zone during electromigration, the complexes with organic solutee must have been in dynamic equilibnum. Mixtures of variow oiganic compounds \vere readily separated by one-way and by two-way electrolysis. In 4 Jf ammonia, pyrogallol migrated to the anode and separated from neutral glucose and sucrose, and weak bases such as triethanolamine separated rapidly from acidic substances such as anthranilic, arsanilic, sa i c y h , and sulfanilic acid. In 0.1 M acetic acid solution, anthranilic acid migrated to the cathode and separated from salicylic acid, which migrated rapidly to the anode, and from p-arsanilic acid, ahich migrated slowly to the anode. By one-way development in 0.1 M acetic acid, sulfanilic acid migrated rapidly to the anode and separated from arsanilic acid, which remained nith neutral surcrose. In succeeding two-way development in the presence of ammonia, the arsanilic acid migrated rapidly to the anode and separated from the neutral sucrov
SUMMARY
Two-way and three-way electrolytic development extend the scope of chromatographic methods. Variation of solvent, with concomitant variation of adsorbability, absorption sequence (15), and ionic mobility, facilitates the resolution of mixtures and the isolation and identification of the components. Accordingly, two-way and three-way electromigration in polyphase systems must be regarded ae extremely sensitive and widely applicable analytical tools. LITERATURE CITED
Callinan, T. D., Lucas, R. T., and Bowers, R. C., “Report of Naval Research Laboratory Progress,” pp. $18, Washington, D. C., May 1951. Consden, T., Gordon, A. H., and Martin, .1.J. P., Biochem. J . , 38, 224 (1944). Cremer, H-D., and Tiselius. .1.,Biochem. Z . , 520, 273 (1950). Durrum, E. L., ,J. A n i . Chem. S O C . , 72, 2943 (1950). Garrison, W. AI., Haymond. €1. R.. arid Maxwell, R. D., J . Chem. Phgs., 17, 665 (1949). Haugaard, G., and Kroner, T. D., J . A m , Chrvn. Soc., 70, 2135 (1948). Kraus, K., and Smith, G., Ibid., 72,4329 (1950). Lederer, E., “ProgrBs recents de la chromatographie.” Paris, Hermann et Cio, 1949. Liesegang, R. E., Natunuisser~.schui‘tan.31, 348 (1943); Z. unul. Chem., 126, 173 (1943). h‘IcDonald, H. J., Urbin, l‘f, C., and Killiamson, M . B.. Sc,ience, 112, 227 (1950). Spiegler, K. S . , and Coryell, C. D., [bid., 113, 546 (1951). Strain, H. H., A s a L . CHEM.,23, 25 (1951). Strain, H. H., in “Frontiers in Colloid Chemistry,” by R. E. Burk and 0. Grummitt, pp, 29-63, New York, Interscience Publishers, 1950. Strain, H. €I., Ind. EnQ.CI~eiia.,42, 1307 (1950). Strain, H. H., IND. ESG. CHEM.,ANAL.ED., 18, 605 (1946). Strain, H. H., .I. Am. Chem. Soc., 61, 1292 (1939). Strain, H. H., and Sullivan, J. C., . ~ N A L .CHEM.,23, 816 (1951). Turba, F., and Enenkel, H. J., Naturwissenschaften, 37, 93 (1950). Wieland, T., and Eischer, E., Ibid., 35,29 (1948); dngew. Chem., A60, 313 (1948); A n n . , 564, 152 (1949). RECEKEDApril 13, 1951.
Analysis of Mixtures of Carboxylic Acids By Spectrophotometric Determination of Rate of Reaction with Diphenyldiazomethane JOHN D. ROBERTS AND CLARE McG. REGAN Department of Chemistry and Laboratory f o r Nuclear Science and Engineering, Massachusetts Institute of Zechnology, Cambridge, Mass.
I
N THE course of investigations (3-4) of the reactions of diazo
compounds with various types of acids, the authors have had occaaion to develop methods for analysis of mixtures of carboxylic acids by measurement of their reaction rates with diphenyldiazomethane. The carboxylic acid-diphenyldiazomethane reaction has obvious advantages for this purpose, as it is very convenient to follow spectrophotometrically (the diazo compound has a deep permanganatelike color), occurs in a wide range of solvents, and may be carried out with small amounts of materials. Furthermore, different carboxylic acids often show substantial differences in rate-for example, p-nitrobenzoic acid reacts approximately 25 times faster than p-aminobenzoic acid in ethyl alcohol a t 30”. The principal disadvantages of the reaction for analytical purposes are the lack of simple stoichiometry in sol-
vents like ethyl alcohol, 15 here the reaction rate is strictly secondorder, and nonintegral kinetic orders in carboxylic acid in aprotic solvents, where the reaction is quantitative. It is the purpose of the present paper to show how these disadvantages may be overcome in the analysis of binary acid mixtures. Detailed procedures for the spectrophotometric determination of the reaction rate of diphenyldiazomethane with acids using a Beckman DU spectrophotometer with a thermostated cell compartment have been published (1-4). In ethyl alcohol, the instantaneous rate of the reaction between carboxylic acids and diphenyldiazometharle is strictly proportional to the first powers of the acid and diazo compound concentrations. However, the acid not only reacts directly to yield the corresponding benzhydryl ester but also catalyzes the forma-
V O L U M E 2 4 , NO. 2, F E B R U A R Y 1 9 5 2
361
Procedures have been developed for the analysis of carboxylic acid mixtures hg spectrophotometric determination of reaction rate with diphenyldiazomethane in alcohol or benzene solution. The median deviations in about 2.5 determinations of different types including mixtures of acetic and benzoic acids, m- and p-methoxybenzoic acids, and acetic and chloroacetic acids were about 29'~.
pound consumption. Rate studies are complicated by the fact that, although the kinetic order with respect to diphenyldiazomethane is exactly first-order, the order with respect to carboxylic acids is not exactly integral in benzene, chloroform, ethylene dichloride, acetonitrile, and acetone (cf. data for benzene in Table I1j, presumably because of association between the acid molecules. As a result, determination of acid mixtures (CBH~~ZCHOOCH -I- K Z by rigorous mathematical analysis of rate curves in (C6H5)2CHOC2Hs +Nf
tion of benzhydi yl ethyl ether through reaction of diphenyldiazomethane with ethyl alcohol (Sj, I s a consequence, the rate does not follow the simple integrated second-order rate equation a t comparable acid and diphenyldiazomethane concentrations (3)
+
( C ~ H , ) ~ C X RCOOH--~-
