Prof, Dcebereiners recent Discovery , to Eudiometry. 317 
apartment, in such a manner that it was freely exposed to the 
air, but protected from dust. At the close of a fortnight, it still 
set fire to hydrogen, though its energy was somewhat diminish- 
ed. Some of the metal was kept a month in a dry bottle, furnish- 
ed with a glass-stopper, and then acted quite well. A platinum 
ball lost and retained its energy under similar circumstances. 
A piece of active platinum invariably failed to give light, if 
kept 24 hours on mercury, the effect being the same whether it 
was covered by an inverted jar or not. On keeping an active 
ball in contact with mercury during two hours, its energy was 
perceptibly impaired. The action of mercury is still more in- 
jurious, when a heated ball is plunged under it, and held there 
during a few seconds. 
Spongy platinum absorbs water greedily when any part of it 
is dipped into that liquid, and then does not become luminous 
under the jet of hydrogen. A platinum ball absorbs water in 
like manner, and in consequence loses its activity. On putting 
a ball thus moistened into mixed oxygen and hydrogen gases, 
an exceedingly sluggish action ensued, during which a large 
quantity of water condensed on the glass. By removing the 
ball successively into fresh portions of the explosive mixture, it 
gradually lost much of its moisture, and regained a great part 
of its former energy, which was not, however, completely re- 
stored till it had been ignited. Similar to this was the effect of 
moistening a ball with alcohol and ether, only the activity re- 
turned more speedily under the same treatment. Spongy pla- 
tinum, if moistened with very strong sulphuric ether, did be- 
come luminous under a continued jet of hydrogen, but when al- 
cohol or water was used it did not. A platinum ball moistened 
with sulphuric, nitric, and muriatic acids, did not act at all on 
an explosive mixture, but ignition restored its activity. 
When platinum is kept for hours in dry oxygen, hydrogen, 
or atmospheric air, it acts afterwards on an explosive mixture 
with its usual activity. An active platinum ball was kept in 
carbonic acid during an hour, and afterwards acted readily on 
an explosive mixture. The same ball was put successively into 
olefiant gas, carbonic oxide, and coal gas, for five minutes, and 
suffered a considerable abatement of its energy in consequence, 
hut still acted. Put into muriatic acid gas, for the same space of 
