OF ARTS AND SCIENCES. 15 



dissolves precisely as in the last-mentioned cases. After the solution 

 of zinc has been added in small excess, white needles separate, which 

 are insoluble in water, and have the formula 



22W0 3 . 9ZnO + 66 aq, 



as the following analyses show : 



1.4620 gr. gave 0.2509 gr. water on ignition, 1.0602 gr. W0 3 and 

 0.1508 gr. ZnO = 17.16% water, 72.52% W0 3 , and 10.31% 

 ZnO. 



7021 100.00 99.99 



The salt was dried for some time upon woollen paper. 



General Conclusions. — From my own investigations, as well as from 

 those of other chemists who have preceded me, I arrive at the fol- 

 lowing classification of the alkaline tungstates as most nearly repre- 

 senting the present state of our knowledge. There are three series 

 of salts, which may be termed respectively normal tungstates, meta- 

 tungstates, and pyro-tungstates. The two first-named series may be 

 represented by the following as typical salts : — 



Normal Series. 

 W0 8 . Na 2 4- 2 aq 



2 W0 3 . Na,0 -j- 6 aq Lefort. 



3 W0 3 . Na 2 -j- 4 aq " 



Meta- Tungstates. 



4 W0 3 . Na 2 -f 10 aq or W 4 O u (NaO) 2 + 10 aq Scheibler 

 6 W0 8 . 2 BaO -f 12 aq " W 6 16 (Ba0 2 ) 2 -f 12 aq " 



8 W0 3 . 3 (NH 4 ) 2 + 8 aq " W 8 21 (NH 4 0) 6 -j- 8 aq Marignac. 



10 W0 3 . 4 Na 2 + 23 aq " W 10 O" 26 (NaO) 8 + 23 aq 



12 W0 8 . 5 Na 2 -f 28 aq « W 12 O~ 31 (NaO) 10 + 28 aq Marignac. 



14 WO a . 6 Na 2 -j- 42 aq « W H 3 ,(NaO) 12 -f 42 aq 



The salts of the normal series require no special notice. As already 

 stated, I have not succeeded in preparing the di-and tri-salts of Lefort, 

 but there seems to be no reason to doubt their existence. The pyro-salts 

 are obtained from the meta-salts by ignition, as insoluble crystalline 

 masses, which are decomposed by long boiling with water. All the 



