er they had acted upon dilute
sulphuric acid, and introducing them into separate tubes containing mixed
oxygen and hydrogen, it was found that the _positive_ pole effected the
union of the gases, but the negative pole apparently not (588.). It was
ascertained also that no action of a sensible kind took place between the
positive pole with oxygen or hydrogen alone.

568. These experiments reduced the phenomena to the consequence of a power
possessed by the platina, after it had been the positive pole of a voltaic
pile, of causing the combination of oxygen and hydrogen at common, or even
at low, temperatures. This effect is, as far as I am aware, altogether new,
and was immediately followed out to ascertain whether it was really of an
electric nature, and how far it would interfere with the determination of
the quantities evolved in the cases of electro-chemical decomposition
required in the fourteenth section of these Researches.

569. Several platina plates were prepared (fig. 57.). They were nearly half
an inch wide, and two inches and a half long: some were 1/200dth of an
inch, others not more than 1/600dth, whilst some were as much as 1/70th of
an inch in thickness. Each had a piece of platina wire, about seven inches
long, soldered to it by pure gold. Then a number of glass tubes were
prepared: they were about nine or ten inches in length, 5/8ths of an inch
in internal diameter, were sealed hermetically at one extremity, and were
graduated. Into these tubes was put a mixture of two volumes of hydrogen
and one of oxygen, at the water pneumatic trough, and when one of the
plates described had been connected with the positive or negative pole of
the voltaic battery for a given time, or had been otherwise prepared, it
was introduced through the water into the gas within the tube; the whole
set aside in a test-glass (fig. 58.), and left for a longer or shorter
period, that the action might be observed.

570. The following result may be given as an illustration of the phenomenon
to be investigated. Diluted sulphuric acid, of the specific gravity 1.336,
was put into a glass jar, in which was placed also a large platina plate,
connected with the negative end of a voltaic battery of forty pairs of
four-inch plates, with double coppers, and moderately charged. One of the
plates above described (569.) was then connected with the positive
extremity, and immersed in the same jar of acid for five minutes, after
which it was sepa