ON LAPIS PONDEROSUS 213 



SECTION IV. 



Now, as the earth separated from tungsten by the nitrous 

 acid is calcareous (Sec. in. (&)), it became necessary to try 

 whether the above-mentioned acid, combined with calcareous 

 earth, would constitute a regenerated tungsten. Having this 

 in view, and knowing that tungsten is not soluble in boiling 

 water (Sec. n. (a)), I mixed one part of the acid solution 

 (Sec. in. (d)) with six parts of clear lime-water, upon which 

 the mixture became a little turbid ; but as, after an interval 

 of some hours, there was no deposition, the mixture was 

 made to boil, when immediately a white heavy powder 

 separated, which, after being dried, gave a sea-green colour 

 to glass of microcosmic salt, became bluish on being boiled in 

 the vitriolic acid, and of a lemon colour with the nitrous and 

 marine acids, and consequently was pure tungsten. 



SECTION V. 



To ascertain more completely the nature of this acid, the 

 following experiments were made : (a) Under the blowpipe 

 the dry acid became first of a reddish yellow colour, then brown, 

 and at last black. It neither smoked nor gave any signs of 

 fusion. (&) With borax it produced a blue, and with 

 microcosmic salt a sea-green glass. This colour is subject to 

 the same changes as are related of the glass (Sec. I. (&)). (c) 

 When pulverised acid of tungsten is boiled with a small 

 quantity of the nitrous or marine acids, the powder becomes 

 yellow; a.nd with the acid of vitriol, bluish, (d) If the 

 solution of the acid of tungsten in water (Sec. in. (d)) be 

 saturated with alkali of tartar, a neutral salt is obtained in 

 very small crystals, (e) With volatile alkali this acid forms 



