|
+---------------+----------+----------+----------+----------+
| Mean | 1.22 | 1.15 | 1.43 | 1.21 |
+---------------+----------+----------+----------+----------+

Since 1.22 cubic centimetres of hydrogen at the temperature 15 deg. C.
and pressure 760 mm. of mercury are liberated by the passage through
acidulated water of one electromagnetic unit of electricity or 3 X
10^10 electrostatic units, and since in one cubic centimetre of the
gas there are 2.46 N atoms of hydrogen, we have, if E is the charge in
electrostatic units, on the atom of hydrogen in the electrolysis of
solutions

2.46NE = 3 X 10^10,

or

NE = 1.22 X 10^10.

The mean of the values of Ne in the preceding table is 1.24 X 10^10.
Hence we may conclude that the charge of electricity carried by a
gaseous ion is equal to the charge carried by the hydrogen atom in the
electrolysis of solutions. The values of Ne for the different gases
differ more than we should have expected from the probable accuracy of
the determination of D and the velocity of the ions: Townsend (_Proc.
Roy. Soc._ 80, p. 207) has shown that when the ionization is produced
by Rontgen rays some of the positive ions carry a double charge and
that this accounts for the values of Ne being greater for the positive
than for the negative ions. Since we know the value of e, viz. 3.5 X
10^-10, and, also Ne, = 1.24 X 10^10, we find N the number of
molecules in a cubic centimetre of gas at standard temperature and
pressure to be equal to 3.5 X 10^19. This method of obtaining N is the
only one which does not involve any assumption as to the shape of the
molecules and the forces acting between them.

Another method of determining the charge carried by an ion has been
employed by Rutherford (_Proc. Roy. Soc._ 81, pp. 141, 162), in which
the positively electrified particles emitted by radium are made use
of. The method consists of: (1) Counting the number of [alpha]
particles emitted by a given quantity of radium in a known time. (2)
Measuring the electric charge emitted by this quantity in the same
time. To count the number of the [alpha] particles the radium was so
arranged that it shot into an ionization chamber a small number of
[alpha] particles per minute; the interval between the emission of
individual particles was several seconds. When an [alpha] particle
passed into the vess