New Substance discovered in Davidsonite. 42i) 



mineral contained a substance quite different in its proper- 

 ties from alumina, or any other of the earthy bases, and 

 the most obvious method of separating it from any of these 

 latter, which might occur along with it, appeared to be by 

 means of sulpho-hydrate of ammonia. 



A. 100 grains of the mineral were finely pounded, and 

 fused with 300 grains of carbonate of soda. The fused mass 

 was treated in the usual manner, and the silica separated 

 by a filter. 



B. To the concentrated solution and washings from (A), 

 sulpho-hydrate of ammonia was added. Avery bulky dark 

 green precipitate fell, which was filtered and washed. 



C. The liquid which passed through the filter (B), was 

 concentrated, and oxalate of ammonia added. No preci- 

 pitate appearing, the evaporation was continued to dry- 

 ness, and a very small quantity of magnesia, obtained in 

 the usual way. 



It appears from this analysis, that if we except the mi- 

 nute portion of magnesia, the mineral is composed entirely 

 of silica, and the substance precipitated by sulpho-hydrate 

 of ammonia. The next point was to determine what this 

 substance was, and as its distinguishing character seemed 

 to be its solubility in caustic alkalies, the sulphuretwas de- 

 composed by nitro-muriatic acid, and treated with caustic 

 ammonia in a well-stoppered bottle, which was occasionally 

 agitated, to promote the solution. The digestion was con- 

 tinued for a fortnight, and the clear liquid, drawn off, at 

 first every 24 hours, and latterly once in two or three days. 

 The precipitate, during the continuance of the digestion, 

 gradually assumed a reddish brown colour, and its solu- 

 bility evidently diminished as the colour deepened, till at 

 last the quantity dissolved by the caustic ammonia became 

 so very small, that it appeared useless to carry the diges- 

 tion any further. The portion remaining undissolved, 

 which amounted to nearly one half of the whole, was there- 

 fore again dissolved in muriatic acid. To this solution, 

 caustic soda was added in excess, and a white precipitate 

 fell, which, when the liquid was boiled, partly dissolved, 

 and partly assumed a brown colour. The whole was thrown 

 upon a filter, which collected the brown matter, while a 

 colourless solution passed through. 



