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IKTRODUCTIONAmong the characteristics of the gallium-indium-thallium family essential to its systematic study are trends and variations in basicity. The combined effects of small size and comparatively high charge among the tripositive ions of these elements should render all of them quite highly acidic, but significant differences should be discernible as these factors vary. Variations in basicity hare been studied as part of a general investigation of comparative properties in this family. I t is the purpose of this communication to summarize results obtained with gallium(II1) compounds by the techniques of electrometric titration with alkali and measurement of pH as a function of salt concentration and to compare them with existent data for indium(II1) compounds.Previously reported measurements of these types have been limited in number and lacking in agreement. Fricke and Meyring (3) obtained data, based upon a hydrogen electrode study of titration of gallium(II1) chloride solutions with sodium and potassium hydroxides, which indicate precipitation of the hydrous oxide (9) in the vicinity of pH 2.8-3.1. Von Bergkampf (15) reported precipitation from hydrochloric acid solution at pH 3.4 and from sodium hydroxide solution at pH 9.7 as a result of single titrations of 0.1 N gallium(II1) chloride solutions, a quinhydrone electrode being used. More recently Ivanov-Emin and Rabovik (5) found from a hydrogen electrode study that precipitation from 0.01 M gallium(II1) chloride solutions began at pH 3.48-3.50 with 2.6 equivalents of sodium hydroxide added and was complete at pH 6.7-6.8 with 2.8-2.9 equivalents. With 0.005 M gallium(II1) sulfate solutions, however, precipitation began at pH 3.4C-3.45 with 0.2 equivalent and was complete at pH 4.7-4.8 with 2.5-2.6 equivalents. Dissolution of the hydrous precipitate at pH 9.6-9.7 after addition of 4.0-4.2 equivalents of alkali was considered evidence for the formation of the species [Ga(OH)J-in solution. Lacroix (8) obtained precipitation from 0.007 M gallium(II1) chloride solution at ca. pH 3.2 and dissolution of the hydrous oxide over a broad range above pH 6.Hydrolysis studies on gallium(II1) salt solutions appear limited to those of Fricke and his coworkers (2, 3). A preliminary measurement (2) of hydrogenion concentration showing 0.1875 N gallium(II1) chloride solution to be 32.9 per cent hydrolyzed was followed (3) by similar measurements as functions of

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185soluble in solvents such as acetone, ethyl ether, benzene, carbon tetrachloride, and absolute ethanol. However, it reacts with water to give an orange solution, which, when evaporated at room temperature or on a steam bath, yields the original blue compound. This behavior is probably due to a hydration reaction (with the subsequent ionization of the chlorides) followed by a dehydration reaction (with the recoordination of the chlorides).