Electro-chemistry. Part I, General theory / by R.A. Lehfeldt ... Including a chapter on the relation of chemical constitution to conductivity, by T.S. Moore.

  • Lehfeldt, R. A. (Robert Alfred), 1868-1927.
Date:
1904
Catalogue details

Licence: In copyright

Credit: Electro-chemistry. Part I, General theory / by R.A. Lehfeldt ... Including a chapter on the relation of chemical constitution to conductivity, by T.S. Moore. Source: Wellcome Collection.

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    for instance, in the electrolytic cell of Fig. i by the appearance of 8 grms. of oxygen at the anode and x'0075 grms. of hydrogen at the cathode. But it often happens that more than one reaction occur simultaneously : in this case the laws must be taken as meaning that the total amount of material deposited at the anode makes up one gram-equivalent, and the same at the cathode. Thus, if current were passed through a solution containing copper and nickel under such conditions that they come down together, one faraday might deposit (on the cathode) x equivalents of copper and y of nickel; but it would be found that x + y = 1. Substances deposited on the anode are called anions, those deposited on the cathode cations, the term ion being given by Faraday to the particles that he assumed to travel through the electrolyte. Accordingly, a cation travels in the nominal direc- tion of the electric current (Fig. 1), while an anion travels against it. Cations include all the metals and hydrogen; anions, chlorine, bromine, iodine, fluorine, groups such as N0*, -SO.,, and acid radicles generally (as well asL QH). It will be seen from the above classification that electrolytes are very commonly salts. Solutions of acids, bases, and salts in water are, indeed, the electrolytes most commonly dealt with; but similar solutions in pyridine, liquid ammonia, and various other solvents are also electrolytes; so are fused salts, and even a certain number of solids, to a slight-degree ; while electrolytic decomposition of gases has also been ob- served. When a process of electrolysis does occur in an unam- biguous way, it may be used to determine the quantity of electricity flowing. A cell arranged for this purpose is known as a voltameter. The chief forms of voltameter are the following :— 1. The Water Voltameter.—In nearly all cases it is the volume of gas evolved that is measured. The oxygen and hydrogen may be collected separately, but that is unnecessary for voltametric purposes, and the instrument takes a simpler form when they are allowed to mix. As electrolyte, dilute sulphuric acid has been much used, but caustic soda is better.