Volume 1

A system of chemistry / by John Murray.

  • Murray, J. (John), -1820.
Date:
1819
Catalogue details

Licence: Public Domain Mark

Credit: A system of chemistry / by John Murray. Source: Wellcome Collection.

Provider: This material has been provided by Royal College of Physicians, London. The original may be consulted at Royal College of Physicians, London.

    614/686 (page 596)
    number of plates, and their size, must be regulated by the purpose to which the trough is to be applied. The wires for conducting and applying the galvanism should be of a metal not liable to chemical change ; those of gold or pla- tina have this advantage. Different liquids are employed to fill the cavities of the trough, and differ much in power. With water, the ef-. feet is very inconsiderable ; with a solution of sea salt (mu- riate of soda) or of muriate of ammonia, it is much great- er j it is still more so with diluted acids, and these have the farther advantage, that they keep the surface of the plates clean, or at least remove very quickly any crust of oxide which would impede the excitation. Nitrous acid diluted appears to be most powerful. From the experi- ments of Mr Singer *, it appears, that when equal pro- portions of the three mineral acids to a given portion of water are employed, the most intense heat measured by the quantity of iron-wire melted in the galvanic circuit is pro- duced by nitric acid, next to it by sulphuric acid, and least by muriatic acid ; the latter, however, exceeded the others in the length of time during which it retained its pow’er. The extent of dilution requires to be different, according to the size and number of the plates, and according to the effect designed to be obtained ; heat and light are produ- ced in the highest intensity, as the acid is less diluted, while to produce chemical decomposition, it may be more diluted } and a stronger acid is required where a battery of large plates of no great number is employed, than where a battery of small plates of a much greater number is used. When the acid liquor is strong, the action of it on the metals is attended with so much effervescence as to be in- convenient. On an average, nitric acid may be diluted with SO parts of water, muriatic acid with 20 or 25; sul- ])huric acid diluted with 25 of water acts powerfully, but * Nicholson’s Journal, vol. xxiv, p. 175.