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SELECTED ARTICLES. 
irritating, and thereby easily distinguished from chlorine, or 
hydrofluoric acid. When exposed to the air, it does not 
fume, as would be the case were the slightest trace of hydro- 
fluoric acid present. The inside of the vessel is found coated 
with crystals of corrosive sublimate. The gas does not 
extinguish ignited phosphorous or red hot iron wire, and con- 
sequently is, (as Sir H. Davy conjectured,) a supporter of 
combustion. It detonates with hydrogen, forming hydro- 
fluoric acid. Placed over water, the solution (if such) has 
all the properties of hydrofluoric acid, i. e., acts on glass, 
reddens litmus, and gives precipitates with lime and barytes. 
Placed over dry litmus and Brazil wood paper, the former is 
reddened, and the latter turned yellow; in no instance are 
they bleached. When a receiver of the gas is placed over 
wet glass, the glass is strongly acted upon; when the glass is 
carefully dried, the action is not so strong as before. When a 
small piece of dry glass is placed in a perforation in the 
interior of the receiver, the glass is acted upon, but not more 
so than when fluoride of mercury alone is in the vessel; from 
which they conclude that fluorine does not act on perfectly 
dry glass. 
To ascertain the action of the gas on metals, they found it 
necessary to try the separate effects of hydrofluoric acid, 
sublimed fluoride of mercury, and the bichloride of mercury, 
in order to distinguish the action of fluorine from that due to 
the vapor of these substances. For this purpose bismuth and 
palladium, at a moderate heat, and gold at a higher tempera- 
ture, afforded distinguishing tests. To determine the relative 
attraction of fluorine for those metals upon which it does not 
act, except at high temperatures, they used as positive poles 
a battery of sixty pairs of plates, moistened fluoride of lead, 
palladium, platinum, gold, and rhodium. The palladium and 
platinum were always acted upon, the gold occasionally, and 
the rhodium never; from which they suppose that fluorine 
might be obtained in an insulated state, by electrolysing 
fluoride of lead in a tube of fluorspar, using rhodium as a 
positive pole. — Trans, of R. Irish Acad, and Lon. Edin. 
Phil. Mag. and Journ. of Science. 
