A manual of electro-metallurgy / By George Shaw.

  • Shaw, George
Date:
1844
Catalogue details

Licence: Public Domain Mark

Credit: A manual of electro-metallurgy / By George Shaw. Source: Wellcome Collection.

    49/226 page 37
    80. The next improvement was introduced by Dr. Wol- laston. He completely surrounded the zinc withthe copper —an alteration which was found to increase the amount of available power, to nearly double that, previously obtained from an equal extent of zinc surface. The improvement which comes next in order is, perhaps, the most im- portant one that has yet been introduced; it is the amalga- mation of the surfaces of the zinc plates by mercury. For this valuable contribution we are indebted to the late Mr. Kemp. 81. It has already been stated (49) that when impure zinc is used in voltaic experiments, the impurities (such as minute portions of charcoal and foreign metals) with which the zinc is contaminated form an infinity of galvanic circles, by virtue of which the metal dissolves. Hence, when ordinary zine is introduced into dilute sulphuric acid, it dissolves rapidly ; and its solution is accompanied with violent effer- vescence, occasioned by the escape of hydrogen. Now, the voltaic electricity, with which the solution of the zinc is ~ accompanied, is, in this case, confined to such minute circles . that we cannot divert it into'a new channel, so as to make it ‘subservient to our purpose; and, as the whole of the zinc dissolved, and acid saturated, yield no current, this local action, as it is called, occasions much waste in the materials of the battery. The improvement in question completely destroys this: local action. 82. By using pure zinc in the construction of voltaic bat- teries, the whole of the chemical action is turned to account; not a particle of zinc is dissolved, but it renders, in an available form, that amount of voltaic electricity which is necessarily associated with such solution, but which, as already explained, with the ordinary metal, is evolved under circumstances which render it useless. (79.) The use of _ pure zinc in the construction of voltaic’ batteries would be attended with such expense, as to completely prevent its
    digitised image 1
    digitised image 2
    digitised image 3