Interferences of Various Substances 107

the whole volume of gas acted upon. Nor was the retardation
so great in any case as might have been expected from the
mere dilution of the oxygen and hydrogen, and the consequent
mechanical obstruction to its contact with the platina. The
order in which carbonic acid and these substances seemed to
stand was as follows, the first interfering least with the action;
nitrous oxide, hydrogen, carbonic acid, nitrogen, oxygen: but it
is possible the plates were not equally well prepared in all
the cases, and that other circumstances also were unequal;
consequently more numerous experiments would be required
to establish the order accurately.

385. As to cases of retardation, the powers of olefiant gas
and carbonic oxide have been already described. Mixtures of
oxygen and hydrogen, containing from ^-th to 7/(>th of sul-
phuretted hydrogen or phosphuretted hydrogen, seemed to show
a little action at first, but were not further affected by the
prepared plates, though in contact with them for seventy hours.
When the plates were removed they had lost all power over
pure oxygen and hydrogen, and the interference of these gases
was therefore of a different nature from that of the two former,
having permanently affected the plate.

386. A small piece of cork was dipped in sulphuret of carbon
and passed up through water into a tube containing oxygen
and hydrogen (374), so as to diffuse a portion of its vapour
through the gases. A plate being introduced appeared at first
to act a little, but after sixty-one hours the diminution was
very small. Upon putting the same plate into a pure mixture
of oxygen and hydrogen, it acted at once and powerfully, having
apparently suffered no diminution of its force.

387. A little vapour of ether being mixed with the oxygen
and hydrogen retarded the action of the plate, but did not pre-
vent it altogether. A little of the vapour of the condensed oil-
gas liquor1 retarded the action still more, but not nearly so
much as an equal volume of olefiant gas would have done. In
both these cases it was the original oxygen and hydrogen
which combined together, the ether and the oil-gas vapour
remaining unaffected, and in both cases the plates retained the
power of acting on fresh oxygen and hydrogen.

388. Spongy platina was then used in place of the plates,
and jets of hydrogen mingled with the different gases thrown
against it in air. The results were exactly of the same kind,
although presented occasionally in a more imposing form.

1 Philosophical Transactions, 1825, p. 440.

the combination of the first por-