120 Journal of the Mitchell Society [February 



has been found possible, however, to obtain by other means a well- 

 defined, crystalline product whose composition is represented by the 

 formula SZrOj.SSOa.HHiO, and a potassium compound, 4Zr02. 

 5SO3.K2O. The following additional scheme of hydrolysis has been 

 proposed : 



4Zr(S04)j + 8H,0 = Zr^lSOOeH* + 2H2SO4 

 Zr4(S04).. (0H),.H4 + 2HsO = Zr4(S04)6. (0H)g.H2 + 2H,S04 

 Zr4(S04)». (0H)..H2 + 2H»0 = Zr4(S04),(OH),o + 2H,S04 



Zr4(S04)2(OH)„ 



2Zr4(S04),(OH)io + 2HiO = ySO* + HiS04 



Zr4(S04)j(OH)„ 

 The compounds Zr4(SO4),(OH)8.H4.10H2O and 4H2O have been ob- 

 tained as crystals, and also the compounds Zr4(S04)3(OH)io and 

 (Zr4(S04)2(OH)„)2S04.8HA but the compound Zr4(S04)5(OH)s.H, 

 only in the form of an alkali salt. In preparing these the colloid is 

 removed by dialysis and these half-colloids crystallized from the 

 concentrated solutions. 



The complex and varying products obtained by mixing a solution 

 of zirconyl sulphate with one of potassium sulphate have long been a 

 puzzle. In part, at least, mixtures of hydrolyzed substances are 

 formed. Recently it has been shown that if the mixed solutions are 

 concentrated over sulphuric acid definite compounds crystallize. 

 These show very well the influence of such a salt as potassium sul- 

 phate upon a progressing hydrolysis. When potassium sulphate is 

 used micro-crystalline needles with the composition K4Zr4(OH)8 

 (804)5.81120 are obtained. In a solution strongly acid with sulphuric 

 acid the first crystals formed are K4Zr(S04)4; in weakly acid solutions 

 the composition is that of potassium-zirconium hydroxysulphate of 

 varying composition. These products hydrolyze on being treated 

 with water. If boiled with water, they become opalescent with 

 colloidal zirconium hydroxide. Following the crystaUizations in 

 detail, the above-mentioned potassium-zirconium hydroxysulphate 

 K4Zr4(OH) 9(804) 6.8H2O forms a crystalline crust of needles. A 

 second crop of prismatic crystals is formed and this has the composi- 

 tion K4Zr (804)4.51120. The first crystals in hydrolyzing increase 

 the free acid and bring about an equilibrium. The formation of the 

 second then begins and decreases the amount of free acid. The reac- 

 tion is thereupon reversed and the hydroxysulphate crystals form 

 once more. 



