OP ARTS AND SCIENCES. 11 



Marignac gives eleven molecules of water. Scheibler gives the 

 formula 7 W0 3 . 3 K 2 -f- 6 aq, but his analyses agree better with 

 that of Marignac. 



When normal potassic tungstate, W0 4 K 2 , is evaporated to dryness 

 with boric hydrate, and the soluble salts are washed out from the 

 mass, a salt is obtained which after recrystallization has the formula 



10WO 3 • 4K 2 + 9aq. 



The same salt is formed when cold solutions of potassic nitrate or bro- 

 mide are added to cold solutions of the 10:4 sodium salts. It resembles 

 the 12:5 potassium salt, already described, so closely, that it is difficult 

 to distinguish between the two. This salt has not been described by 

 other writers upon the subject. In preparation a, from the action of 

 boric acid upon normal potassic tungstate, 



0.4566 gr. gave 0.3714 gr. W0 8 = 81.34% 



0.5915 gr. lost on ignition 0.0331 gr. water = 5.59% 



. In preparation b, from the action of acetic acid upon the normal 

 potassium salt, 



0.7418 gr. gave 0.6024 gr. W0 3 = 81.21% 



1.1104 gr. lost on ignition 0.0610 gr. water = 5.49% 



0.7060 gr. gave 0.5736 gr. W0 3 = 81.27% 



1.0266 gr. lost on ignition 0.0556 gr. water = 5.42% 



These analyses correspond best with the formula 



IOWO3. 4K 2 + 9aq. 



2859.6 100.00 



It is probable that the salt had lost a little water by efflorescence. 

 When normal potassic tungstate is dissolved in boiling water, it is 

 decomposed into free alkali and 12 : 5 acid tungstate. The decomposi- 

 tion may be represented by the equation, 



12 (W0 3 . K 2 0) + 7 II 2 = 12 W0 3 . 5 K 2 + 14 KHO. 



In the acid salt formed in this manner, 



0.7738 gr. lost on ignition 0.0414 gr. water = 5.35% 

 1.0385 gr. gave 0.8411 gr. W0 3 = 80.99% 



