FIoccuIation of a hydrophobic colloid on the addition of electrolytes occurs as a result of neutralizdon of the electrical charge of the coIIoid particles by the adsorption of oppositely charged ions. In this phenomenon, there is a linear relationship rule between the charge number of the counter ion to he adsorbed and the logarithm of the minimal concentration of it that will cause flocculation. This empirical rule was also verified'*' with complex salts, and the application of floccuiation in the determination of the charge number of complex ions was suggested.
We previously investigated the relationship between hydration and association of ions by studying the electrophoretic and chromatographic behaviour of a series of inert cobalt(III) complexes3* The results indicated that strongly hydrated complexes associate more with strongly hydrated anions and weakly hydrated complexes associate more with weakly hydrated anions. Our results were supported by the chromatographic examination on alumina by Lederer and Battilotti', and their results on silica gel agreed closely with our investigations.
Thus, it was recognized that association of ions is dependent not only on the ionic charge but also on the state of hydration of ions. As the flocculation of a hydrophobic colloid is caused by the association of counter ions with the colloidal particles, it is reasonable to presume that factors which govern kcculation are not only the ionic charge but also the state of hydration of the counter ions to be adsorbed. In other words, the difference in the state of hydration of ions should be reflected by differences in flocculation values. Therefore, if we determine the flocculation values of a series of ions which have the same charge but are in different states of hydration, a wide range of values will be obtained.
In this study, we prepared a series of he xammine-type cobalt@) complexes and determined their flocculation values for colloidal As&, and these values were compared with the R, values in thin-layer chromatography on silica gel.
EXPERIMENTAL
Preparation of the kxammine-type cobalt(Ill) complexes