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.

    119/330 (page 101)
    half the electrolyte is ionised; so that for binary electrolytes, in comparing the ionisation-constants, we are comparing the concentration necessary to produce a given degree of dis- sociation, viz. 50 per cent. All electrolytes are, according to theory, entirely ionised at infinite dilution. Practically, a great many electrolytes are fully ionised at dilutions of 1024 or 2048 litres. In such solutions, the equivalent conductivity depends entirely on the ionic velocity and on the magnitude of the charges carried by the ions. This was discovered by Kohlrausch, and may be 1 expressed in the form : The equivalent conductivity of an clectro- i lyte in very dilute solution is the sum of two quantities, one 1 characteristic of the anion, and the other of the cation. (For the meaning of equivalent conductivity, see p. 58.) Since the mobility of the hydrogen ion is so much greater l than that of any other ion, the conductivity of a solution of an :acid is mainly due to the hydrogen ions present. From this it follows that the molecular conductivity of a di-basic acid is approximately double that of a mono-basic acid at dilutions at which both the compounds are fully ionised. (The molecular (conductivity is the conductance of that volume of the solution 'which contains one gram-molecule of the electrolyte.) A similar ^statement applies to bases, since the mobility of OH', though much less than that of hydrogen, is still considerably larger tthan that of any other ion. Examples may be seen in the Tables given (p. 102). Inorganic Acids.—The inorganic acids, for the most part, belong to the class of good conductors, and do not obey lOstwald’s dilution law. It is therefore necessary to compare tthe respective degrees of ionisation for each dilution. The following values for the molecular conductivity are taken from iLeitvermo^en der Elektrolyte (Kohlrausch and Holborn), pp. 160 and 167. The constants for carbonic acid, sulphuretted hydrogen, and hydrocyanic acid are taken from Walker’s1 (results. 1 /. C.S., 77. p. 8 (1900).