C hap. ax.] Regiilus of fungftein. 127, 



tion. The regulus is not acled on by the vitriolic and 

 marine acids ; the nitrous' acid, however, and aqua- 

 regia, aft on it, and by oxygenating it reduce it 'to its 

 calciform ftate. 



M. Lavoifier recommends the following procefs for 

 obtaining the calx of tungftein : i 1 "' 'ix one part of ore 

 of tungftein with four parts of mild vegetable alkali, 

 and rnelt the mixture in a crucible, which ought to 

 be of platina ; then powder, and pour on twelve parts 

 of boiling water ; add pale nitrous acid, and the tung- 

 ftenic acid precipitates in a concrete form. After- 

 wards, to infure the complete oxygenation of the 

 metal, add more pale nitrous acid, and evaporate to 

 drynefs, repeating this operation as long as red fumes 

 are produced from the acid. 



In the ftate of yellow calx it has the following pro- 

 perties: it is perfectly infipid and infoluble in water; 

 if triturated in water it limply diffufes through it like 

 an emulfion, and takes fome months to depofit from 

 it. If volatile alkali is poured on it, it whitens, which 

 inftantly diftinguifhes it from the yellow calx of ura- 

 nite, which will fhortly be mentioned. 



