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 



22 W0 3 . 9 ZnO + 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 3 . Na 2 -f 2 aq 

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

 3W0 3 .Na 2 + 4aq 



Meta- Tungstates. 



4 W0 3 . Na 2 + 10 aq or W 4 0„(NaO) 3 -f- 10 aq Scheibler 



6 W0 3 . 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 -f- 8 aq Marignac. 



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



12 W0 3 . 5 Na 2 -j- 28 aq " W 12 O 31 (NaO) I0 -f- 28 aq Marignac. 



14 W0 3 . 6 Na 2 -j- 42 aq " W 14 36 (NaO) ]2 + 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 



