216 Description and Analysis of the Sillimanite. 
mes. The loss of moisture by a calcination was, therefore, 
015 grammes, or 0.50 per 100. i 
B. The calcined mineral was then treated with three 
times its weight of caustic potash, and the mixture exposed 
to a red heat, during one hour, in a silver crucible. The 
contents of the crucible after exposure to heat, were of a 
light brown colour. The fused mass was treated wiih mu- 
riatic acid in excess, and the fluid evaporated to dryness. 
Water acidulated with muriatic acid was then added, and 
the whole thrown upon a filter. The silex separated in 
this manner when washed and calcined amounted to 1.293. 
grammes, or 43 per cent. 
C. The muriatic solution (B) was then decomposed at a 
boiling heat, by sub-carbonate of ammonia, and the precipi- 
tate which was produced, having been well washed, was 
treated repeatedly with caustic potash, in order to separate 
the alumine. This alkaline fluid was supersaturated with 
muriatic acid, and then treated with sub-carbonate of am- 
monia in excess. The alumine which was precipitated, 
amounted when washed and calcined to 1.626 grammes, or 
54.310 per cent. 
D. That portion of the mineral which remained after 
the action of the potash, was of a browncolor. It was dis- 
solved in muriatic acid, the excess of acid neutralized by 
potash and hydro- sulphuret of potash then added, which 
caused a black precipitate. This precipitate after being 
heated to expel the sulphur, was treated with a little nitric 
acid and calcined. It weighed 0.62 grammes or 2 per 
cent, and was pure peroxide of iron. 
E. The liquor (D) from waich the iron had been pre- 
cipitated by an hydrosulphuret, was then tested with oxa- 
late of ammonia, and with phosphate of soda and ammonia, 
but gave no indications of the presence of either lime or 
magnesia. 
The result of this analysis gives as the constituents of this 
mineral, 
