ON LAPIS PONDEROSUS 211 



melted, was poured out on an iron plate, and dissolved in 

 twelve parts of boiling water. After standing some hours, 

 the lixivium was poured off from a portion of white powder 

 which had subsided to the bottom, (d) This powder was 

 edulcorated, and nitrous acid added to it, till no more 

 effervescence could be perceived, by which operation great 

 part of it was dissolved, (e) The undissolved part of the 

 powder was dried, and, being again mixed with four parts of 

 alkali of tartar, was fused as before. This mass being also 

 dissolved in water, and nitrous acid poured upon the remain- 

 ing powder, only a very small portion of grey powder was 

 left behind undissolved. (/) The ley (c) was saturated with 

 nitrous acid ; it grew thick by the precipitation of a white 

 powder, which was afterwards washed with cold water and 

 dried, (g) The solution in nitrous acid (d) afforded, on the 

 addition of alkali of tartar, a white precipitate, which was 

 dried. 



SECTION II. 



(a) Boiling water has no action upon tungsten reduced 

 to powder. (&) On one part of finely powdered tungsten 

 were poured two parts of concentrated acid of vitriol, and 

 the mixture was distilled. The acid passed over unchanged ; 

 and the residuum, which was of a bluish colour, was boiled a 

 short time in distilled water, which was then filtered off, 

 and upon cooling deposited some vitriolated lime, (c) On 4 

 scruples of tungsten, reduced to a very fine powder, were 

 poured 12 scruples of common nitrous acid, or pure 

 aquafortis ; no effervescence ensued ; the mixture was then 

 exposed to a strong digesting heat, whereupon the powder 

 soon assumed a citron-yellow colour. The acid was then 

 decanted off into a separate .phial ; and the yellow powder, 



