492 



Chemical Analysis of Tabasheer. 



[Oct. 



3. Ten grains of tabasheer reduced to a fine powder were digested 

 in distilled water for 24 hours. The water when concentrated was 

 tasteless ; but slightly reddened vegetable blues. Being evaporated to 

 dryness, grayish scales remained, weighing 0*6 gr. These scales 

 being digested in muriatic acid, a little iron was dissolved, but the 

 scales consisted almost entirely of silica. Thus, it appears, that the 

 silica in the tabasheer is still soluble in water. I am disposed to con> 

 sider, the reddening of vegetable blues in this case, as produced by the 

 dissolved silica; at least, I did not succeed in finding any trace of any 

 other acid substance. When the muriatic acid dissolved upon the 

 scales was evaporated to dryness, a brown matter remained, which be- 

 sides iron, contained also a trace of vegetable matter ; but too small 

 to admit of examination. It contained also a little lime and a little 

 silica. 



4. Ten grains of tabasheer reduced to a fine powder, were mixed 

 with 24 grains of finely pounded fluor spar, and the whole was made 

 into a thin magma by means of sulphuric acid. This mixture was ex- 

 posed for some hours to the heat of the sand bath in a platinum cruci- 

 ble. After the exhalations of fiuosilicic acid had ceased, the crucible 

 was exposed to a heat gradually increased to redness, and kept in that 

 temperature till all the excess of sulphuric acid had been driven off. 

 The white matter in the crucible (chiefly of lime) was now lixiviated 

 with water, till every thing soluble was taken up. The water thus em- 

 ployed, was mixed with some carbonate of ammonia, and filtered to 

 separate the lime which it had dissolved in the state of sulphate. 

 The water, thus nearly freed from lime, was reduced to a small 

 quantity, by evaporation, and, while still hot, was mixed with a 

 few drops of solution of oxalate of ammonia, to throw down a little 

 lime which had either escaped the action of the carbonate of ammo- 

 nia, or had been afterwards supplied by the filter. The mixture was 

 allowed to stand till it became clear, the liquid was then drawn off with 

 a sucker, evaporated to dryness, and the saline residue exposed to a red 

 heat. A salt remained, which weighed 0*2 grains, and which proved, 

 on examination, to be sulphate of potash, equivalent to Oil grain 

 potash. 



5. Ten grains of tabasheer in the state of a fine powder were inti- 

 mately mixed with 20 grains of anhydrous carbonate of soda, and the 

 mixture exposed in a platinum crucible to a red heat, raised at last 

 sufficiently high to bring the whole into a state fusion. The colour of 

 the fused mass was yellowish brown. It was dissolved in muriatic acid 

 the solution evaporated to dryness, and the residue, after being digested 

 a sufficient time in muriatic acid, was thrown on the filter. The silica 

 edulcorated, dried and ignited weighed 9 grains. 



6. The muriatic acid, in which the silica had been digested being 



