8 PROCEEDINGS OF THE AMERICAN ACADEMY 



Twelve to Five Sodium Salt. — This is the salt to which Scheibler 

 gives the formula 



7W0 8 .3Na 2 0+16aq, 



and which Marignac writes 



12W0 3 . 5 Na 2 -f 28 aq. 



According to Lotz, the salt contains fourteen atoms of water in place 

 of sixteen as found by Scheibler. I have adof)ted the formula of 

 Marignac, which agrees best with the analyses. In preparing this salt 

 I have employed Scheibler's method, which consists in nearly neutral- 

 izing a boiling solution of the neutral tungstate, W0 4 Na 2 -\- 2 aq, by 

 chlorhydric acid. When the proper quantity of chlorhydric acid is 

 added, the 12:5 salt is formed at once, and crystallizes from the solution 

 in large colorless crystals, which, according to Scheibler, are mono- 

 clinic ; according to Marignac, triclinic. If the proportion of chlor- 

 hydric acid is just sufficient to give an onion-red reaction with litmus, 

 crystals are obtained, which are either a combination or a mixture of 

 equal molecules of the 10:4 and 12:5 salts. These crystals are, accord- 

 ing to Dr. Gooch, triclinic; their habitus resembles that of the 12:5 

 rather than that of the 10:4 salt. In this salt, in two different prepa- 

 rations carefully dried and pressed with woollen paper, 



H 



f 1.2546 gr. gave 0.9725 gr. W0 3 = 77.51 % 



j 1.2320 gr. " 0.9554 gr. " = 77.55% 



1.4G80 gr. lost 0.2035 gr. water = 13.86% 



[1.7511 gr. " 0.2431 gr. " =13.88% 



f 1.0842 gr. gave 0.8407 gr. W0 3 = 77.54% 



1 1.0908 gr. " 0.8450 gr. " =77.47% 



" 1 1.6919 gr. lost 0.2362 gr. water = 13.96% 



[ 1.5259 gr. " 0.2125 gr. " =13.93% 



The analyses agree closely with the formula 



12 WO a . 5 Xa.O 4- 10 W0 8 . 4 Na 2 -f 51 aq, 



6580 100.00 100.00 



