4o8 ESSAYS AND OBSERVATIONS 



in order to feparate this acid from it, we 

 add an alkali which has been previoufly de- 

 prived of its air ; by which means, the chalk 

 itfelf is alfo obtained free of air, and in an a- 

 crid form, or in the form of flaked lime. 



We have alfo feveral proceffes for obtain- 

 ing the volatile alkali in a cauftic form, which 

 feem to be only fo many methods of obtain- 

 ing it in its pure ftate, and free of fixed air. 

 The firft of thefe is the feparation of the al- 

 kali from an acid, merely by heat ; an in- 

 ftance of which we have from Mr. Mar- 

 graaf'^\ He prepared from urine an ammo- 

 niacal fait, the acid of which is the bafis of 

 the phofphorus, and is of fuch a peculiar na- 

 ture, that it endures a red heat without being 

 diffipated. Sixteen ounces of the neutral fait 

 were fabjedled by him to diflillation. The 

 acid remained in the retort, and he found in 

 the receiver eight ounces of an alkaline fpirit, 

 which, he tells us, was extremely volatile, 

 very much refembling the fpirit of fait am- 

 moniac diftilled with quick-lime ; and no 

 cryftals were formed in it, when expofed to 

 the cold air. 



A 



,i:f Mem. del'Acad. de Berlin, an. 1746, p. S;* 



