and capable of carrying a quarter ampere without much heating, and R', a dial resistance-box in parallel with R. R', the resistance of which should be some thousands of ohms, serves as a fine adjustment. The current is allowed to flow for an exactly measured interval, say two hours, and kept adjusted by manipulating R' so that there is no deflection of G. The current is then calculated from the weight of silver, and when multiplied by the resistance S, gives the electromotive force of the standard cell. This method is, however, only of a secondary nature since it requires a knowledge of the electrochemical equivalent of silver, which can only be obtained by means of the electro-dynamometer or current-balance.

TABLES

I. EQUIVALENT WEIGHTS (w) AND ELECTRO-CHEMICAL EQUIVALENTS
IN GRAMS (X) OF IONS.

3. MIGRATION RATIOS OF ANION. (In aqueous solution of concentration
m gram-equivalents per litre (Kohlrausch and Holborn).)

The following are from more recent experiments :-

NOYES AND SAMMET, Zeitschr. phys. Chem. 43. 49 (1902).

'54

*530

*70

S། ། །

JAHN, Zeitschr. phys. Chem., 37. 673 (1901).

Limiting values for indefinite dilution (Temperature 18-19°).

*268

4. CONDUCTIVITY OF STANDARD SOLUTIONS (see p. 55).

5. EQUIVALENT CONDUCTIVITIES OF AQUEOUS SOLUTIONS
(see diagrams, pp. 60, 61).

6. IONIC CONDUCTIVITIES AT 18° (KOHLRAUSCH AND HOLBORN).

Cl.

I. NO3. CIO3. C2H3O2. SO4. C2O4. CO3. OH.

The above numbers serve to calculate approximately the
equivalent conductivities of compounds of univalent ions, and
of univalent with bivalent ions (except H.SO.). For compounds
of bivalent anions with bivalent cations the following table is
to be used:-

T. P. C.

S

The limiting values 4 for infinite dilution at 18°, and the

temperature coefficients (17) 18

are (Kohlrausch and von

dl
dt

Steinwehr, Berl. Akad. Sitzber, 26. 570, 581 (1902):--

7. DISSOCIATION CONSTANTS K (calculated by Ostwald's equation from
the MOLECULAR conductivity).

68.7

0'0227

Formic acid

Acetic acid.
Propionic acid
Glycollic acid
Malic acid
Tartaric acid

Benzoic acid

Salicylic acid

At 25°.