INQUIRIES RESPECTING FLUORIC ACID. <gj \ 



After this combustion, either the whole or a part of the Product of the 

 fluoric acid, according- as the quantity of potassium is great com ustlon * 

 or small, is found to be destroyed or absorbed. A mass of 

 a chocolate colour remains at the bottom of the retort ; and 

 a sublimate, in some parts chocolate, and in others yellow, 

 is found round the sides, and at the top of the retort. 



When the residual gas afforded by this operation is Residual gas, 

 washed with water, and exposed to the action of an electri- ° 

 cat spark mixed with oxigen gas, it detonates and affords a 

 diminution, such as might be expected from hidrogen gas. 



The proportional quantity of this elastic fluid differs a its proportion. 

 little in different operations. When the fluoric acid has 

 not been artificially dried, it amounts to one sixth or one se- 

 venth of the volume of the acid gas used ; but when the 

 fluoric acid has been long exposed to calcined sulphate of 

 soda, it seldom amounts to one tenth. 



I have endeavoured to collect large quantities of the cho- Attempt to 

 colate coloured substance for minute examination ; but some collect large 



quantities of 



difficulties occurred. the product. 



When I used from eighteen to twenty grains of potas- 

 sium, in a retort containing from twenty to thirty cubical 

 inches of fluoric acid gas, the intensity of the heat was such 

 as to fuse the bottom of the retort, and destroy the results. 



In a very thick plate glass retort, containing about nine- successful 

 teen cubical inches of gas, I once succeeded in making a one. 

 decisive experiment on ten grains and a half of potassium, 

 and I found, that about fourteen cubical inches of fluoric 

 acid disappeared, and about two and a quarter of hidrogen 

 gas were evolved. The barometer stood at 30*3 t and the 

 thermometer at 6l° Fahrenheit; the gas had not been arti- 

 fically dried. In this experiment there was very little sub- 

 limate ; but the whole of the bottom of the retort was co- 

 vered with a brown crust, and near the point of contact with 

 the bottom, the substance was darker coloured, and ap- 

 proaching ia its tint to black. 



When the product was examined by a magnifier, it evj- Productacom- 

 dently appeared consisting of different kinds of matter: a P yund * 

 blackish substance, a white, apparently saline substance, 

 and a substance having different shades of brown and fawn 

 colour. 



The 



