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This investigation of the solubilities of the isomeric nitro benzoic acids in various liquids was undertaken with the purpose of acquiring data which could be used for systematic correlations. It was hoped that comparison of these data with those obtained by the authors for the nitranilines* 1 and the amino benzoic acids,2 would permit generalizations which could be applied to various systems of this same type. The selection of the nitro benzoic acids was made primarily to complete the data for all the possible di-substituted benzene derivatives which contain the nitro, amino, and carboxyl groups.Solubility data for these isomeric nitro acids are quite meager. Measurements for these acids have been secured for various temperatures in benzene, heptane and water.3 Determinations at isolated temperatures may also be found for various solvents.

In a previous paper* 1 there were presented series of measurements of the solubility of the three nitroanilines in water, alcohol, benzene, chloroform, carbon tetrachloride, ether, ethyl acetate and acetone; the corresponding solubility curves for the three isomers are in general very similar, yet differ appreciably in some cases, these differences being evidently somehow correlated with the melting temperature (presumably also with the heat of melting) of the crystalline isomer. These results indicated the desirability of investigating similarly a related series of isomers to learn moie as to the degree of similarity which may be expected in such parallel cases. Consequently we have measured the solubility, in the same solvents, of the three aminobenzoic acids, which differ formally from the nitroanilines only in the substitution of a carboxyl group for a nitro group; in chemical behavior they differ specifically in the pronounced amphoteric character of the aminobenzoic acids in aqueous solution, and in the readiness with which they decompose at elevated temperatures.There are few data available on the solubility of the aminobenzoic acids. Flaschner and Rankin2 determined the solubility of each in water at temperatures ranging in the case of the ortho from 84o, of meta from 66°, of para from 47°, up to the respective melting point; de Coninck3 worked with the meta in water from o°-7o°, and there are scattered data in various solvents at temperatures io°-25°. The solvents used in the work here presented are methyl, ethyl, and butyl alcohol, ethyl acetate, benzene and chloroform; the temperature range is from 25°t o the melting temperature of the respective acid except in the case of butyl alcohol in which fewer measurements were made.The materials used, selected from the purest stock obtainable, were purified as follows:Ortho-aminobenzoic Acid. The C.P. acid was crystallized several times from water at about 80°, boiling water being avoided because at that temperature some decomposition of the acid occurs.4 Norite was used as a decolorizer prior to the first crystallization from water. Finally the acid was crystallized from hot chloroform, which yielded a slightly yellow crystalline material. A white product can be obtained if the acid is sublimed, but * From a part of the dissertation presented to the Graduate

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