246 On th6 Cause of Chemical Proporlion?. [April, 



Tungsten SOIG 100 



Oxygen 1 'J-Si 24.75 



10000 



To discover the oxide of tungsten whose composition is propor- 

 tional to that of the sulphuret, I put a portion of tnngstic acid into 

 a glass tube, which 1 heated to redness in a small furnace, while a 

 current of hydrogen gas passed through the red hot acid. Tiie gas 

 at first disappeared and produced vapours of water; but at last 

 passed through the tube without alteration. I continued the cur- 

 rent of hydrogen vi-hile the tube was cooling. I obtained the acid 

 converted* into a flea brown oxide, very inflammable, taking fire at 

 a temperature considerably under a red heat, and burning like 

 tinder, leaving for residue yellowish green tungstic acid. 100 

 parts of this oxide burnt upon a small plate of platinum, produced 

 107 parts of acid of tungsten. But these 107 pa'ts contain 21" 1 6 

 of oxvgen, of which 7 is almost exactly the third part. Hence 

 this oxide is composed of 



Tungsten 85-84 100-0 



pxygcu . . . , 14-16 16-5 



100 00 



This oxide is neither soluble in acids nor alkalies. Jt remains to 

 be examined, wliether it would not unite with acids at the instant 

 of its formation ; as for example, by heating powder of tungsten 

 in muriatic acid gas. 1 ought to observe that Mr. Bucholz, 

 {Neiws Journal fur Chemieund Physik von Schtveiggev, t. 3. p. 15,) 

 makes mention of a brown oxide of tungsten, obtained by the de- 

 composiuon of tungstate of ammonia, which he considers as inter- 

 mediate between the blue oxide and the acid. We shall see imme- 

 diately that these two last bodies constitute in fact one and the 

 same substance. 



To determine the number of volumes of oxygen in tungstic acid, 

 1 examined tungstate of ammonia. This salt was composed with 

 tungstic acid, treated with nitric acid, and then exposed to a red 

 heat. Ammonia dissolves tungstic acid slowly, byt tlie combina- 

 tion obtained is very pure. I put 10 parts of tungstate of ammonia 

 dried and in powder, into a retort exactly weighed, to which I 

 adapted a tubulated receiver filled with caustic potash, 'J'he re- 

 ceiver had a tube attached to it likewise filled with caustic potash. 

 I lieated the retort to redness, and kept it in that state till the dis- 

 engagement of ammonia was over. There remained in the cru- 

 cible 8-S8 parts of an indigo blue powder, exceedingly beautiful. 

 The iTcelver and tube being heated a little to drive off the remains 

 of the ammonia, had^ gained 0-557 in weight, and the lo^s of 

 weight occasioned by the escape of the ammonia amounted to. 

 p-56"3 parts. This experiment w;is repeated several times, and the 



