Page:Proceedings of the Royal Society of London Vol 1.djvu/269

Rh cups, and electriﬁed, the decomposition was more rapid. A solution of sulphate of potash being put into each of the cups, and electriﬁed by means of ﬁfty pair of plates for four hours, the acid was found by itself in the positive cup, and the alkaline bases in the negative cup. Similar phenomena took place with sulphate of soda, nitrate of pot- ash, nitrate of barytes, sulphate of ammonia, and alum. When mu- riatic salts were used, these yielded oxymuriatic acid. When com- patible mixtures of neutro-saline compounds were used, the different acids and bases separated in a mixed state, without any regard to their affinities. When solutions of metals, deoxidizable by nascent hydrogen Were employed, metallic crystals formed on the negative wire, and some oxide was deposited; but solutions of iron, zinc, and tin, only deposited oxide; a great excess of acid was soon observed on the positive side. Although stronger solutions aﬁ'orded signs of decomposition quicker than weaker ones, yet even the smallest pro- portions seemed to be acted upon with equal energy : as paper tinged with turmeric was immediately rendered brown when plunged into pure water and brought into contact with the negative point; so paper tinged with litmus was immediately reddened by the positive point, in consequence of the very minute portion of saline matter contained in the paper; and it further appeared, that in all these decompositions the separation of the constituent parts from the last portions of the compounds was complete when the operation was sufﬁciently protracted.

The contact of the solution with the wires was not necessary for its decomposition; for muriate of potash being put into the middle tube of a series of three, the outer ones containing only water and the Wires, alkali soon appeared in that connected with the negative wire, and acid in the other; and at length they were obtained per- fectly separate.

In thus causing the acids to be thus transferred from a saline com- pound into water, through moistened amianthus, no change was ob- served to take place in litmus paper placed near the amianthus. The reddening of the litmus paper always took place just above the posi- tive point, and then slowly diffused itself to the middle of the vessel. Similar eﬂ’ects were observed when the alkali was transferred, the turmeric paper ﬁrst becoming brown close to the negative wire.

When three glass tubes were used, the two outer tubes holding a solution of muriate of soda, and the middle one sulphate of silver, a communication being made with the central vessel by turmeric paper on the positive side, and by litmus paper on the negative, neither of the papers had its colour changed, although the muriatic acid passing through the amianthus occasioned a dense heavy precipitate in the sulphate of silver, and the soda a more diﬂ’use and lighter one.

Acid or alkaline substances will also pass through liquids, having a strong attraction for them. In an apparatus of three tubes, Mr. Davy found that sulphuric acid, evolved from sulphate of potash, would pass into water, through either ammonia, lime-water, or weak solutions of potash or of soda. The only effect of strong solutions of