m the Nature of certain Bodies. 89 
chocolate coloured substance obtained by lixiviation, it oc- 
curred to me that this matter might be a result of the ope- 
ration, and that the chocolate substance might be a compound 
of the siliceous and fluoric bases in a low state of oxygenation, 
with potash ; and this idea is favoured by some trials that I 
made to separate silex from the mass, by boiling it in con- 
centrated fluoric acid ; the substance did not seem to be 
much altered by this process, and still gave silex by com- 
bustion. 
I endeavoured to decompose fluoric acid gas in a perfectly 
dry state, and which contained no siliceous earth ; and for this 
purpose I made a mixture of one hundred grains of dry bo- 
racic acid, and two hundred grains of fluor spar, and placed 
them in the bottom of an iron tube, having a stop-cock and 
a tube of safety attached to it. 
The tube was inserted horizontally in a forge, and twenty 
grains of potassium, in a proper iron tray, introduced into 
that part of it where the heat was only suffered to rise to dull 
redness. The bottom of the tube was heated to whiteness, 
and the acid acted upon by the heated potassium, as it was 
generated. After the process was finished, the result in the 
tray was examined. 
It was in some parts black, and in others of a dark brown. 
It did not effervesce with water : and when lixiviated, afforded 
a dark brown combustible mass, which did not conduct elec- 
tricity, and which when burnt in oxygene gas, afforded boracic, 
and fluoric acid. It dissolved with violent effervescence in 
nitric acid ; but did not inflame spontaneously in oxymuriatic 
acid gas. 
I have not as yet examined any of the other properties of 
MDCCCIX. N 
