Electro-chemistry Volume 1 - Robert Alfred Lehfeldt, Paperback

• Release Date   5/22/2012
• ISBN-13   9781236445728 | 978-1-236-44572-8
• ISBN   1236445724 | 1-236-44572-4
• Format   Paperback
• Author(s)   Robert Alfred Lehfeldt
• This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1904 Excerpt: ...dealing with methods of measurement below, an indication of the way in which electrode potentials have been determined will be given. for the present we assume the results. The electrode potential then represents the work done in carrying unit quantity of electricity between electrode and electrolyte. and since on the ionic theory the carriage is effected by the formation or discharge of an ion, it is the wofk done in this chemical process that is involved. E.g. at the negative pole of the Daniell we have the reaction Zn = Zn-+ 20 Now it is found that about half a volt difference of potential exists in this case, the metal being negative to the solution. Again, at the other pole of the cell the reaction Cu" + 2 Q = Cu involves a slightly greater potential difference (about o-6 volt), but here the metal is positive to the solution. Consequently the total difference of potential from one electrode to the other is the sum of these, viz. 1-1 volts, as measured. These facts may be expressed by the simple diagram annexed, in which height represents potential: the small difference of potential between the two solutions is ignored. It is a well-known fact that the chemical properties of a solution depend very much on its concentration. thus the affinity that causes nitric acid to Cu-f attack metals is lessened by diluting it with water. The same thing shows itself, of course, in electromotive force measurements, and therefore to get any standard of electrode potential Solution it is necessary to define the concentration of the solution. E.g. zinc will show less tendency to form ions if there are already many zinc ions 2n 'n ke solution, 1-e-if a strong solution of zinc sulphate be used. A concentration which is normal (1 gramequivalent per litre) with respect ...