Solutions of Metallic Salts. 



121 



Experiments toit/i Salts of Zirconium. 



To prepare a standard solution of the salt of zirconium it 

 was found to be most convenient to heat the double fluoride 

 of potassium and zirconium with sulphuric acid, evaporate to 

 dryness in platinum, dissolve the zirconium sulphate remain- 

 ing in water and enough sulphuric acid to prevent the precipi- 

 tation of the basic salt, and dilute to standard volume. Meas- 

 ured portions of the solution were taken from a burette as 

 required for the experiments. The presence, however, of so 

 large an amount of sulphuric acid as was necessary to keep the 

 zirconium salt in solution tends to decompose sodium thiosul- 

 phate so rapidly that it was found necessary to nearly neutralize 

 the solution with ammonium carbonate before adding the 

 sodium thiosulphate. The solution of zirconium sulphate was 

 standardized by precipitating with ammonia aud weighing as 

 the oxide. 



In experiment 1 of Table V, the solutions of zirconium sul- 

 phate and sodium thiosulphate were boiled together for a few 

 minutes and then the precipitate Altered off, ignited and 

 weighed as the oxide. In experiments 2-5 inclusive, similar 

 solutions were submitted to a pressure of 20 atmospheres in 



the digester. 





Table V. 







Zr0 2 taken. 



Na 2 S 2 3 



taken. 



Zr0 2 found. 



Error. 



grms. 



grms 





grms. 



grms. 



1. -0658 



3 





•065 1 



•0007 — 



2. '0658 



3 





•0676 



•0016-f 



3. -0666 



2 





•0670 



•0004- 



4. '0641 



2 





•0648 



•0007-f- 



5. -0641 



2 





•0645 



•0004 -}-- 



These results clearly show that sodium thiosulphate precipi 

 tates zirconium completely as the hydroxide either with 

 without the aid of pressure. 



or 



Experiments with a Salt of Titanium. 



The solution of the salt of titanium was obtained by treating 

 the double fluoride of potassium and titanium with sulphuric 

 acid, evaporating to dryness, and dissolving the residue in sul- 

 phuric acid and water. The solution was standardized by pre- 

 cipitating the titaninm hydroxide with ammonia and then add- 

 ing an excess of acid as recommended by Gooch.* This 

 method of procedure avoids the tendency to excessive weight 

 observed when the titanium hydroxide is precipitated by 

 ammonia in presence of salts of the alkalies. 



* Amer. Chem. Jour., vii, 285. 



