Variation of the Electrodes	i 27
but when to these is added its well-known power of forming a
compound with water, it is no longer surprising that such a
compound should be produced in small quantities at the positive
electrode; and indeed the bleaching power which some philo-
sophers have observed in a solution at this electrode, when
chlorine and similar bodies have been carefully excluded; is
probably due to the formation there; in this manner, of oxy-
water.
 453.	That more gas was collected from the wires than from
the plates, I attribute to the circumstance, that as equal quan-
tities were evolved in equal times,, the bubbles at the wires
having been more rapidly produced, in relation to any part of
the surface, must have been much larger; have been therefore
in contact with the fluid by a much smaller surface, and for a
much shorter time than those at the plates; hence less solution
and a greater amount collected.
 454.	There was also another effect produced, especially by
the use of large electrodes, which was both a consequence and
a proof of the solution of part of the gas evolved there.   The
collected gas, when examined, was found to contain small
portions of nitrogen.   This I attribute to the presence of air dis-
solved in the acid used for decomposition.    It is a well-known
fact, that when bubbles of a gas but slightly soluble in water or
solutions pass through them, the portion of this gas which is
dissolved displaces a portion of that previously in union with
the liquid:  and so, in the decompositions under consideration,
as the oxygen dissolves, it displaces a part of the air, or at
least of the nitrogen, previously united to the acid;  and this
effect takes place most extensively with large plates, because
the gas evolved at them is in the most favourable condition for
solution.
 455.	With the intention of avoiding this solubility of the gases
as much as possible, I arranged the decomposing plates in a
vertical position (442, 443), that the bubbles might quickly
escape upwards, and that the downward currents in the fluid
should not meet ascending currents of gas.   This precaution I
found to assist greatly in  producing constant results,  and
especially in experiments to be hereafter referred to, in which
other liquids than dilute sulphuric acid, as for instance solution
of potash, were used.
 456.	The irregularities in the indications of the measurer
proposed, arising from the solubility just referred to, are but
small, and may be very nearly corrected by comparing the results