Page:Philosophical Transactions of the Royal Society A - Volume 184.djvu/353

$v_{1}=$ 0.00047 centim. per secon,

as the specific ionic velocity of the bichromate group.

This is not given by Kohlrausch, but we can calculate it by his method from known observations. Thus, Lenz has found the specific molecular conductivity of the solution to be $9.10\times 10^{-12}$, and the migration constant was determined by Hittorf, and came out .502.

By Kohlrausch’s theory (see p. 338),

$\mathrm {U} =u+v=10352{\frac {k}{\mathrm {N} }}$
$\,\,\,\,\,\,=10352\times 9.10\times 10^{-8}=.000942$,

therefore,

$v=.000942\times .502$
$\,\,\,\,\,=$ 0.000473.

This close agreement between theory and observation led me to examine a case in which the specific resistances of the solutions were not the same, in order to see whether the method could be used when no solutions could be found with the exact resistance needed. I used potassium bichromate and potassium chloride, whose conductivities are $9.10\times 10^{-12}$ and $11.13\times 10^{-12}$ respectively. If the extension of method is practicable, these solutions should give the same velocity for the bichromate group as the former pair—bichromate and carbonate. The galvanometer was moved, and, therefore, had to be regraduated.

Resistance. 060=54 (°).0 065=52.4 070=51.0 075=49.4 080=48.0 085=46.7 090=45.4 100=43.0 110=40.7 120=38.6 130=36.5

The following results were obtained—

Current Downwards. Motion Upwards.

$v$	=	04.04	04.18	04.18	04.22.	Mean,	004.15.
$\mathrm {G}$	=	40.0	40.0	40.2	40.2	Mean,„	40°.1.

Therefore

$v_{1}=0.000516$.

Current Upwards. Motion Downwards.

$v$	=	05.19	05.18.	Mean,	005.19.
$\mathrm {G}$	=	50.15	49.2	Mean,„	49°.9.

$v_{1}=0.000394$.