140 Analysis of some Steatites. > 



processes employed did not enable me to discover. In con- 

 sequence 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 

 lixivium. At the expiration of a few days I obtained 36 

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

 ration I procured from the mother water 15 parts more of 

 the same salt mixed with a few needly crystals of sulphate 

 of lime. 



2. The stone appearing to me to be but imperfectly decom- 

 posed, I powdered it afresh, and treated it as before. On 

 adding the acid employed in this operation to the mother 

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

 making in all 60 parts. Then, as I employed for this ope- 

 ration very 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. Sixty parts of 

 alum, however, do not require seven of potash, the quantity 

 of loss, but as the stone is very siliceous, it is probable 

 that the whole of the potash was not extracted bv the sul- 

 phuric acid, though I boiled the stone twice in it. 



The speekstein therefore is composed of 



Silex 56 



Alumine 29 



Lime 2 



Jron 1 



Water 5 



Potash 7 



100 



In his analysis of speekstein, M. Klaproth found no 

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

 amounts to 10 per cent., and the loss of 2}, which he ex- 

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

 probable that M. Klaproth estimated the water by compu- 

 tation, and not by direct experiment ; for, to whatever heat 

 I exposed the stone, it never lost more than 5 per cent. 



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