Ionic Mobilities inCl2and inCl2-Air Mixtures

Work of early investigators and of Herbert Mayer indicates that the presence of traces of ${\mathrm{Cl}}_2$ reduces the mobility of the negative ion below that of the positive ion, a fact which appeared inconsistent with a theory of Condon and the writer. No investigations of mobilities of both ions in pure ${\mathrm{Cl}}_2$ have been reported. The possibility that the discrepancy between theory and observation in Mayer's results was caused by HCl in the ${\mathrm{Cl}}_2$ made a more careful investigation imperative. ${\mathrm{Cl}}_2$ carefully prepared and free from both HCl and ${\mathrm{H}}_2$O was used. It was found that the values of the mobilities in pure ${\mathrm{Cl}}_2$ on the new absolute standard for positive and negative ions was 0.654 and 0.510 cm/sec per volt/cm respectively. A study of mixtures of dry air and ${\mathrm{Cl}}_2$ showed that traces of ${\mathrm{Cl}}_2$ less than 0.1 percent reduce the negative mobility below that of the positive ion. The positive mobilities were little affected by the presence of ${\mathrm{Cl}}_2$ so that while positive ions obey Blanc's law in ${\mathrm{Cl}}_2$-air mixtures the negative ion shows a marked clustering effect. No disturbances due to dipole moments were observed for positive ions in ${\mathrm{Cl}}_2$ as is to be expected.