1 836. J 



Chemical J na lysis of Tabasheer. 



493 



concentrated, was mixed with caustic ammonia. Yellow flocks fell, 

 which were separated hy decantation : these flocks, when ignited, 

 became dark brown, and weighed 0-1 grain ; they dissolved readily in 

 muriatic acid. The solution, was super-saturated with caustic potash, 

 and digested on the sandbath for 24 hours. By this means 0-01 grain 

 of alumina was dissolved. The rest consisted of peroxide of iron. 

 Thus, the yellow flocks thrown down by caustic ammonia, consisted of 



Peroxide of iron, 0'09 



Alumina, 0 01 



01 



The liquid from which this precipitate had fallen was not rendered 

 muddy by carbonate of ammonia. It was, therefore, evaporated to dry- 

 ness. A greyish matter remained weighing 0-08 grain. This matter 

 being digested in muriatic acid, there remained undissolved 0-05 grain 

 of silica. The 0-03 grain dissolved, consisted of a mixture of alumina 

 and lime. 



Thus, the constituents obtained were, 



Moisture, 0-487 or 4-8? 



Silica, 9-050 „ 90-50 



Potash, 0-110 „ 1-10 



Peroxide of iron, 0-090 „ 0*90 



Alumina, 0-040 „ 0-40 



9-777 97-77 



The loss, amounting to 2-23 per cent, was probably the consequence 

 of my employing different portions of the tabasheer in different steps 

 of the analysis. For they were not all exactly the same in appearance. 

 Hence, possibly the proportion of the constituents might vary some- 

 what in each. But my supply of tabasheer was not sufficiently great 

 to admit of a new analysis upon a large scale. I did not weigh the 

 lime; but do not think it could exceed 0-1 per cent. It is needless to 

 observe, that the preceding analysis accords sufficiently with the expe- 

 riments of Mr. Smithson and Dr. Turner, and, therefore, serves to con- 

 firm them. The tabasheer examined by Smithson, Turner, and myself 

 was from India; that subjected to examination by Fourcroy and Yau- 

 quelin was from South America. It remains to be seen whether the 

 constitution of the American tabasheer be essentially distinct from the 

 Indian, as would appear from the 30 per cent, of alkali, &c. found in it 

 by Fourcroy and Vauquelin. — Records of General Science, for February r , 

 1836. 



