116 Journal of the Mitchell Society [February 



presence of water. When water is excluded normal zirconium salts 

 can be formed from it. When hydrolyzed, zirconyl hydroxide ZrO 

 (0H)2 is formed. This hydroxide is amphoteric, behaving as a base 

 towards strong acids and as an acid towards strong bases. It shows 

 little tendency to form definite compounds with weak acids or bases. 

 As a base it gives zirconyl salts, and these may be hydrolyzed into 

 basic zirconyl salts. As an acid, called zirconic acid H2Zr03, it forms 

 zirconates, chiefly with the alkalies and alkaline earths. These are 

 very slightly soluble in water and are decomposed by mineral acids. 



Zirconium shows many and close analogies to the other elements 

 in the fourth group, both as to the compounds formed and their 

 chemical behavior. This analogy is especially close in the cases of 

 titanium and tin when they are quadrivalent. In limitation of val- 

 ence it is more like carbon and silicon. Its occurrence as the dioxide 

 is also characteristic of the group. The ease of hydrolysis and the 

 amphoteric character of the hydroxide are also group characteristics. 



The outstanding characteristics of the compounds in which tetra- 

 valent zirconium is directly united with an acid radical is their marked 

 tendency to react with water. Ignorance of this or failure to consider 

 it has led to many mistakes on the part of earlier investigators. 

 Older statements represent such salts as the tetrachloride, the sul- 

 phate, the fluoride, and others as crystallizing unchanged from aqueous 

 solutions, but later investigators have shown that none of these 

 salts can exist in water solutions and most of them are unstable in 

 the presence of the slightest moisture. 



Hydrolysis takes place not merely with readiness, the water pro- 

 duced in a gas burner hydrolyzing normal zirconium sulphate which 

 is being heated by it, but also to a far-reaching extent. The velocity 

 of the reaction and the extent depend upon the dilution, the tempera- 

 ture, and the time. The content of such a solution then is determined 

 by its previous history. The hydrolysis is progressive and the acid 

 radical may be gradually liberated until very little is left in combina- 

 tion, the small remaining portion being held probably by adsorption. 

 In the case of the chloride, for instance, the amount of chlorine left 

 has been found to be about 3 p.c. of the amount originally present, 

 and this is no longer precipitated by silver nitrate unless first treated 

 with nitric acid. When dialyzed this chlorine is found with the 

 colloidal hydroxide in the hydrogel. This hydrogel consists in the 

 main of zirconyl hydroxide. Experiments with the sulphate yield 

 similar results. The normal hydroxide is unstable in the presence of 



