14 PROCEEDINGS OF THE AMERICAN ACADEMY 



10 WO, . 4 Na 2 + 4 S0 4 Zn = 6 WO,, . 2 ZnO -f 2{2 W0 8 . ZnO} 



+ 4S0 4 Na 2 . 



The zincous ditungstate, as Lefort has shown, is readily soluble in 

 water and remains in solution. 



When a cold solution of zincous sulphate is added to a cold solution 

 of the 10:4 sodium salt, a different result is obtained. A white precipi- 

 tate is at first formed as before, which instantly redissolves. After a 

 small excess of the sulphate has been added, the solution gives in a 

 short time colorless needles of a second zinc salt. Like the 6 : 2 salt 

 first described, this is insoluble in water, cold or hot, but readily dis- 

 solves in an excess of the tungstate or sulphate. When a large excess 

 of the sulphate is present, the zincous tungstate does not separate from 

 the solution. Of this salt in one preparation, dried over S0 4 H 2 : 



0.6586 gr. lost on ignition 0.0706 gr. water = 10.72% 



n KQQ , ( 0.0638 gr. ZnO = 10.82% 



0.5894 gr. gave 1 ° J 



8 s (0.4606 gr. W0 3 =78.16% 



These analyses lead to the formula 



10WO 3 . 4ZnO+ 18 aq, 



In a second preparation of the same salt, dried by woollen paper, 



1.0006 gr. gave by ignition 0.1663 gr. water, also 0.7322 gr. W0 3 

 and 0.1048 gr. ZnO = 16.62% water, 73.18% W0 3 , and 10.47% 



3166 100.00 100.27 



When a cold solution of zincous sulphate is added to a cold solu- 

 tion of the 22-atom sodium salt a precipitate is formed, which re- 



