ESSAY III. 



CHEMICAL INVESTIGATION OF FLUOR ACID, WITH A VIEW 

 TO THE EARTH WHICH IT YIELDS, BY MR. WIEGLEB. 



SECTION I. 



THE observation communicated by Mr. Margraaf to the 

 Academy of Sciences at Berlin in 1768, 1 that a peculiar 

 volatile earth might be obtained by distillation from fluor, 

 to which vitriolic acid had been added, probably gave occasion 

 to Mr. Scheele to make some experiments with a view to 

 this. They have served to show the truth of what Margraaf 

 had said concerning the volatile earth. But Mr. Scheele 

 has attempted to advance farther, and to explain the 

 singular phenomenon which this earth exhibits. 



SECTION II. 



It appears from his Essay that he does not consider 

 the earthy matter as coming from the fluor, from which 

 there is only a very peculiar acid sui generis expelled by 

 the vitriolic acid. He supposes that the fluor acid, which 

 arises in the form of vapour, combines with the water as 

 soon as it reaches its surface, and thus changes it into earth, 

 constituting the crust which appears on the surface of the 

 water during the operation. At the same time he takes 

 it for granted, without expressly mentioning it, that another 



1 Memoires, torn. xxv. for 1768. 

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