72 Faraday's Researches

and transfer of elements upon the chemical affinity of the sub-
stances present, experiments were made upon sulphuric acid
in the following manner. Dilute sulphuric acid was prepared,:
its specific gravity was 1021.2. A solution of sulphate of soda
was also prepared; of such strength that a measure of it con-
tained exactly as much sulphuric acid as an equal measure of
the diluted acid just referred to. A solution of pure soda, and
another of pure ammonia, were likewise prepared, of such
strengths that a measure of either should be exactly neutralised
by a measure of the prepared sulphuric acid.

262. Four glass cups were then arranged, as in fig. 15; seven-
teen measures of the free sulphuric acid (261) were put into
each of the vessels a and b, and seventeen measures of the
solution of sulphate of soda into each of the vessels A and B.
Asbestus, which had been well washed in acid, acted upon by

Fig. 15.

the voltaic pile, well washed in water, and dried by pressure,
was used to connect a with b and A with B, the portions being
as equal as they could be made in quantity, and cut as short as
was consistent with their performing the part of effectual com-
munications, b and A were connected by two platina plates
or poles soldered to the extremities of one wire, and the cups a
and B were by similar platina plates connected with a voltaic
battery of forty pairs of plates four inches square, that in a
being connected with the negative, and that in B with the posi-
tive pole. The battery, which was not powerfully charged, was
retained in communication above half an hour. In this manner
it was certain that the same electric current had passed through
a b and A B, and that in each instance the same quantity and
strength of acid had been submitted to its action, but in one
'case merely dissolved in water, and in the other dissolved and
also combined with an alkali.

263. On breaking the connection with the battery, the por-
current passing through it, rather than to the poles, as they are