1931] The Chemical Behavior of Zirconium 119 



supposition, its formula may be written KaZrFs. It is formed when 

 the potassium fluoride and zirconium fluoride are mixed in equivalent 

 proportions. 



Zirconium sulphate also affords a very instructive example of 

 hydrolysis. So complicated are the different directions which this 

 hydrolysis takes and so varied are the products formed that it has 

 been the subject of skilled investigation for the past two decades, 

 and many mistakes have been made from the earliest time up to the 

 present. Some of the problems involved still lack a satisfactory 

 solution. The normal sulphate was long supposed to exist in two 

 crystalline forms — the anhydrous, Zr(S04)2, and the tetrahydrated, 

 Zr(S04)2.4H20. The first crystalhzed from concentrated sulphuric 

 acid and its formula is correctly given. The second crystalhzed from 

 aqueous solutions, presumably without change. It has been shown 

 since that the latter is really an hydrolysis product. The hydrolysis 

 proceeds as follows: Zr(S04)2.4H20 = Zr(S04)2+H20+3H20 = ZrOS04. 

 H2SO4.3H2O. Of course, such hydrolysis would not be revealed by 

 analysis. A solution of this acid compound reacts with certain 

 reagents in a manner different from a freshly-prepared solution of 

 Zr(S04)2 and which is only slightly hydrolyzed. If sulphuric acid is 

 added to this fresh solution of zirconium sulphate the same reactions 

 are shown. The mere presence of free acid might serve as an explana- 

 tion without the assumption of an acid compound but would leave 

 the inhibitory effect upon hydrolysis unexplained. Observations 

 based on physical methods also corroborate the view that an acid 

 compound is present. There seems to be no inherent obstacle to 



writing this formula as a hydrogen zircon yl sulphate, ZrOs— SO4. 



Similar acid complexes are given with the nitrate, perchlorate, and 

 compounds with certain organic acids. 



One of the other possible series of hydrolytic changes has also 

 been traced analytically. Zr(S04)2+H20=ZrO(S04)2H2. 2ZrO(S04)2 

 H2 + H20=Zr 203(804) 2H2+H2SO4. Electrolytic dissociation yields 

 respectively the anions ZrO(S04)2 and Zr203(S04)2. These compounds 

 occur in solution along with strongly hydrolyzed basic zirconyl 

 products, as is evidenced by the composition of the precipitates ob- 

 tained from these solutions on the addition of alcohol. Such preci- 

 pitates are usually poorly defined and seemingly amorphous. It 



