b PROCEEDINGS OF THE AMERICAN ACADEMY 



In \ 1.3594 gr. lost on ignition 0.1862 gr. water = 13.70% 

 ' (0.5340 gr. gave 0.4155 gr. WO, = 77.80% 



IV ( 1.1660 gr. lost on ignition 0.1624 gr. water = 13.93% 

 " 1 0.5981 gr. gave 0.4659 gr. WO a = 77.89% 



v ( 1.3594 gr. lost on ignition 0.1862 gr. water = 13.70% 

 ' X 0.5340 gr. gave 0.4155 gr. W0 3 = 77.80% 



The formula 10 WO, . 4Xa.,0 -f 23 aq requires 



Calc'd. 1. 2. 3 4. 5. Forcher. Marignao. 



10WO a 2320 77.80 77.99 77.85 77.80 77.89 77.80 77.82 77.88 



4XaX> 248 8.32 8.13 8.21 8.50 8.18 8.50 8.16 8.39 



23H.,6 414 13.88 13.88 13.94 13.70 13.93 13.70 13.88 13.53 



2982 100.00 99.86 99.80 



The means of all these analyses may be compared with the three 

 formulas above given. 



For the ratio 10 . 4 . 22 



" 10 . 4 . 24 



" 10 . 4 . 23 

 Means of new analyses, 



The analyses therefore leave no reasonable doubt as to the true 

 constitution of the salt. The solution of the 10 : 4 sodic tungstate has a 

 distinct acid reaction, but it is very difficult to determine the limits of 

 the basicity in this series, because no salts could be obtained having a 

 number of molecules of fixed base higher than four. On the other 

 hand, the white insoluble mass obtained by igniting the crystalline 

 hydrate must have the formula 



10 WO, . 4 Na^O, 



and I consider it a true pyro-salt. When boiled for some time with 

 water, the pyro-salt dissolves and the original salt crystallizes from 

 the solution. The case appears to be exactly analogous to that of 

 sodic metatungstate, the insoluble 



4 W0 3 . Na 2 

 of Scheibler and Marignac, giving the normal sodic metatungstate, 

 4WO, . Na 2 0-f 10 aq, 



when heated with water in a sealed tube. The reactions of the 10:4 salt 

 with metallic solutions are extremely similar to those of the 12 : 5 salt, 



12W0 3 . 5Xa 2 0-f 28 aq, 



