(S04)2.12H20-KAl (S04)2.12H20, and NH4Cr- (S04)2.12Hz0-KCr(S04)~. 12H20. 2. The thallium-ammonium alum pair follows Vegard's law perfectly, while the other two pairs deviate slightly from the law. The difference in size of the substituting ions is important in determining deviations from Vegard's law, but seems to have little bearing on the distribution ratios between liquid solutions and solid solutions and their deviation from the ideal case. No change in ...