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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.

TABLES

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

(The faraday is taken as 96,600 coulombs.)

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

At atmospheric temperature. Small print indicates uncertain values.

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The following are from more recent experiments :—

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

*216

268

*686

*695

*709

*72 73 112 118 435 434 421 *54 *548 546

404 380 *355

*74 *75

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

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

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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).

K. Na. Li. NH4. Ag. Ba. Sr. Ca. Mg. Zn. H

Normal

ity (m).

65 3 444 35'5 64°2 55'7 573 540 53'0 49

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Cl.

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

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

T. P. C.

S.

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

temperature coefficients (d) are (Kohlrausch and von

18

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

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7. DISSOCIATION CONSTANTS K (calculated by Ostwald's equation from the MOLECULAR conductivity). At 25°.

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