Disappearance of Gases Around the Poles 85

inches in length and three-fourths of an inch in diameter, had
two platina poles fixed into its upper, hermetically sealed,
extremity: the poles, where they passed through the glass, were
of wire; but terminated below in plates, which were soldered to
the wires with gold (fig. 16). The tube was filled
with dilute sulphuric acid, and inverted in a cup
of the same fluid; a voltaic battery was con-
nected with the two wires, and sufficient oxygen
and hydrogen evolved to occupy four-fifths of
the tube, or by the graduation, 116 parts. On
separating the tube from the voltaic battery the
volume of gas immediately began to diminish,
and in about five hours only 13! parts remained,
and these ultimately disappeared.

303. It was found by various experiments
that this effect was not due to the escape or
solution of the gas, nor to recombination of the
oxygen or hydrogen in consequence of any
peculiar condition they might be supposed to
possess under the circumstances; but to be
occasioned by the action of one or both of the
poles within the tube upon the gas around them.
On disuniting the poles from the pile after 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 (324). It was
ascertained also that no action of a sensible kind took place
between the positive pole with oxygen or hydrogen alone.

304. These experiments reduced the phenomena to the con-
sequence 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.

305. Several platina plates were prepared (fig. 17). They
were nearly half an inch wide, and two inches and a half long:
some were ¥J-0dth of an inch, others not more than -(rJ1Tdth,
whilst some were as much as T^th of an inch in thickness. Each
had a piece of platina wire, about seven inches long, soldered to

Fig. 16.ey find matter of a contrary kind capable of