This latter gas has been collected over mercury, and
accurately characterized.
Deville's adamantine boron burns in the same manner, but with more
difficulty, becoming fluoride or boron. The small quantity of carbon
and aluminum which it contains impedes the combination. Arsenic and
antimony in powder combine with this gaseous body with incandescence.
Sulphur takes fire in it, and iodine combines with a pale flame,
losing its color. We have already remarked that it decomposes cold
water, producing ozone and hydrofluoric acid.
The metals are attacked with much less energy. This is due, we think,
to the small quantity of metallic fluoride formed preventing the
action being very deep. Iron and manganese in powder, slightly heated,
burn with sparks. Organic bodies are violently attacked. A piece of
cork placed near the end of the platinum tube, where the gas is
evolved, immediately carbonizes and inflames. Alcohol, ether, benzol,
spirit of turpentine, and petroleum take fire on contact.
The gas evolved at the negative pole is hydrogen, burning with a pale
flame, and producing none of these reactions.
When the experiment has lasted several hours, and there is not enough
hydrofluoric acid left at the bottom of the tube to separate the two
gases, they recombine in the apparatus in the cold, with violent
detonation.
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