526. Four glass cups were then arranged, as in fig. 55; seventeen measures of the free sulphuric acid (525.) 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 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 communications, _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 positive 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. 527. On breaking the connexion with the battery, the portions of asbestus were lifted out, and the drops hanging at the ends allowed to fall each into its respective vessel. The acids in _a_ and _b_ were then first compared, for which purpose two evaporating dishes were balanced, and the acid from _a_ put into one, and that from _b_ into the other; but as one was a little heavier than the other, a small drop was transferred from the heavier to the lighter, and the two rendered equal in weight. Being neutralized by the addition of the soda solution (525.), that from _a_, or the negative vessel, required 15 parts of the soda solution, and that from _b_, or the positive vessel, required 16.3 parts. That the sum of these is not 34 parts is principally due to the acid removed with the asbestus; but taking the mean of 15.65 parts, it would appear that a twenty-fourth part of the acid originally in the vessel _a_ had passed, through the influence of the electric current, from _a_ into _b_.