ON FLUOR 17 



SECTION XXX. ON ABSORBENT EARTHS. 



(a) A solution of lime in fluor acid remained clear till 

 the acid was saturated ; but then the whole quantity of 

 dissolved earth united with the acid into a mass, which 

 partly precipitated and partly congealed with the liquid into 

 a jelly in the open air, and proved to be regenerated fluor. 



(b) Magnesia, dissolved in the fluor acid, partly pre- 

 cipitated immediately with it, and in part formed a jelly. 



(c) Pure clay, or earth of alum, formed with the fluor acid 

 a sweet solution, which also formed a jelly. 



SECTION XXXI. ON METALS. 



The under-mentioned metals were digested with fluor 

 acid in separate glass vessels for six hours. The liquor was 

 made to boil towards the end. They showed the following- 

 phenomena : 



(a) Gold was not attacked. The fluor acid showing in 

 some particulars a resemblance with muriatic acid, I was 

 induced to try whether it would dissolve gold, when mixed 

 with nitrous acid, as muriatic acid does ; but without success. 



(b) Neither did silver undergo any change. The calx 

 of silver, precipitated by an alkali, was partly dissolved ; 

 but the remainder united with the fluor acid into an insoluble 

 mass, which lay at the bottom of the vessel. On pouring 

 vitriolic acid upon it, the fluor acid was expelled, under its 

 common form of a corrosive vapour. 



(c) Quicksilver was not dissolved ; but the calx of 

 quicksilver, precipitated from nitrous acid by fixed alkali, 

 was dissolved in part. The remaining insoluble part united 

 with the acid, and formed a white powder, from which the 



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