The Mobility of Argon and Hydrogen Ions in Air

The apparatus and method are the same as previously used to measure the mobilities of air, C${\mathrm{O}}_2$ and other ions in air, the freshly formed ions being driven across a stream of air by means of an electric field. Two positive ions and one negative ion were found in both argon and hydrogen as in the case of air. The initial positive hydrogen ion was found to transform into the second, and this is doubtless also true in the case of argon, though it was not proved. The mobilities are also the same as obtained for the air ions except in the case of the negative hydrogen ion which has a higher mobility than the negative air ion. It is thus found that the following monomolecular ions all have the same mobility in air at normal pressure: monatomic A, initial + and -; diatomic air, initial + and -; diatomic ${\mathrm{H}}_2$, initial +; triatomic C${\mathrm{O}}_2$, initial + and -. Thus the mobility of these ions seems to be independent of the masses. The only exception so far found is the negative ${\mathrm{H}}_2$ ion.