PHYSICAL AND LITERARY. s^S 



fixed alcallne fait to the crude fal ammo- 

 niac : Now, as we can prepare an extem- 

 poraneous or artificial fait, by impregna- 

 ting the volatile fait or fpirit of fal-am- 

 moniac with the fpirit of fea fait, we 

 have no reafon to doubt, but, by means 

 of a fixed alcallne fait, we may again dif- 

 engage the volatile fait or fpirit from the 

 acid. 



But it may be of more importance to 

 difcover what kind of acid is joined to 

 the volatile alcali in the common or crude 

 fal-ammoniac : For this purpofe I made 

 the following experiment. When all the 

 volatile fait and fpirit are drawn off from 

 crude fal-ammoniac by the addition of a 

 fixed alcaline fait and water, there remains 

 a faline mafs j which, when diiTolved in 

 warm water, the folution ftrained and e- 

 vaporated, the chryftals very much re- 

 femble thofe of fea- fait, in fhape, tafte, 

 and other diflinguilhing charatSters of 

 that fait, efpecially when it is well depu- 

 rated and carefully chryftallized. This 

 fait, however, has been dignified with the 

 title of fal febrifugum Sylvii. I put three 



ounces 



