1Y4t ANALYSIS OF SOME STEATITES, 



compact talc contained some other principle, which the pro- 

 Treated with cesses employed did not enable me to discover. In conse-* 

 sulphuric acid, q^gnce I treated a hundred parts, reduced to fine powder, 

 with concentrated sulphuric acid. 



I . After boiling for two hours I dried the mixture, lixi- 

 viated the residuum with distilled water, and boiled the 

 Cubic crystals hxivium. At the expiration of a few days I obtained S6 

 of alum ob- parts of alum crystallized in cubes: and by a second evapo- 

 tained, ration I procured from the mother water 15 parts more of 



the same salt, mixed with a few needly crystals of sulphate 

 of lime. 

 Treated with 2. As the stone appeared to me but imperfectly decom- 

 fresji sulphuric p^g^^j^ j powdered it afresh, and treated it as before. On 

 adding the acid employed in this operation to the mother 

 and more alum water of the preceding, I obtained 15 parts more of alum, 

 produced. making in all 6o parts. Then, as I employed for this opera* 

 lion veiy pure sulphuric acid, and added no potash to the 

 solution, it is evident, that the stone contained a certain 

 portion of this alkali, and that this substance was the occa- 

 sion of the loss I had in the first analysis. 

 The whole of Sixty parts of alum however do not require seven of pot- 

 bab!y not ex- ^^^» ^^^ quantity of loss; but as the stone is very siliceous, 

 traded. it is probable, that the whole of the potash was not ex- 



tracted by the sulphuric acid, though I boiled the stone 

 twice in it. V 



The specksteln therefore is composed of 

 Its true compo. '■ 



nc^mparts. gilex s6 



Alumine 29 



Lime 2 



Iron 1 



Water 5 



Potash 7 



100 



Kiaproth Mr. Klaproth, in his analysis of speckstein, found no 



leckous too potash : but the quantity of water, which according to him 

 muchwa^r. ' i , , ,. t i • T i 



amounts to 10 per cent, and the loss ot 2f , which he ex- 

 perienced, will just balance the deficiency I found. It is 

 probable, that Mr. Klaproth estimated the water by com- 

 pulation. 



