337 
nitric acid; in this experiment there was no subfluoride of 
iron formed, but the vessel was found to contain fluosilicic 
acid gas. 
“In athird experiment a piece of charcoal was employed, 
which had been previously freed from all metallic impurities 
and from silica, by being first boiled in pure nitric acid, and 
afterwards in hydrofluoric acid. Employing this purified 
charcoal as the positive electrode, I obtained no immediate 
action upon the litmus paper; but after the action had conti- 
nued for two hours, it was found to be completely bleached, 
while the gold had undergone no sensible action. That the 
bleaching was not due to the action of the vapour of hydro- 
fluoric acid was ascertained, by leaving litmus paper for 
several hours in the neck of a platinum retort, from which 
hydrofluoric acid was distilling. 
“ The battery was now kept in action for fifteen hours, at 
the end of which time the vessel being examined, the litmus 
had disappeared, and the gold leaf showed signs of having 
been strongly acted upon, having assumed a dark brownish 
colour, and having gathered itself into little balls, as if it 
had undergone the action of heat. The platinum wire was 
acted upon in those parts where it was in contact with the 
charcoal, but no where else. 
** When the platinum wire forming the positive electrode 
passed through the stopper to the bottom of the vessel, the 
hydrogen, in place of rising through the perforation in the 
stopper, as in the former instance, rose now into the re- 
ceiver, where, upon applying a light, it exploded, showing 
that it does not enter into combination with fluorine without 
the aid of heat. The presence of the vapour of hydrofluoric 
acid in the vessel prevented me from determining by other 
experiments how far fluorine was a supporter of combustion. 
‘‘ To determine the colour of the gas, a stopper of fluorspar 
similar to the former was made to fit one of the transparent 
fluorspar receivers formerly described. The gas evolved in 
the receiver appeared colourless. 
