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EFFECT OF GASES ON POSITIVE IONS 243

in the following table. The values for the negative emission
under similar conditions are added for comparison:—

Oxygen

Air

Nitrogen
Hydrogen
Hydrogen

Pressure A / A i

(mm,). -I- -I - -

ss 7x10™ 1-52 x To⁴ 4xio^aft 678 x io⁴

760 7 x io'^IH 2-46 x io⁴ lo'-'¹ 4-49 x io⁴

2*8 4 x ro'*ⁿ 3-56 x to⁴ 3 x ro^<J« 5*6 x io⁴

i'9 to^lt{ 170 x io⁴ J.o'^w 474 x jo⁴

226 io'^t() ^-85 x xo⁴ 3 x io^ul 278 x io⁴

It is a remarkable fact that the constants for the positive

emission, in the table above, exhibit a linear relation between
log A and b similar to that shown by the constants for the nega-
tive emissions from platinum and tungsten, which was con-
sidered in Chapter IV. Moreover, the constant a{c> or r,

considered on p, 137, has a very similar value, being equal to
1*43 x io¹¹ for the positive emission from platinum in various

gases, as compared with the values 3-29 x io^y for the nega-
tive emission from platinum and 2*56 x io^:{ for the negative
emission from tungsten. We have seen that, in the case of the
negative emissions, the linear relation in question is closely
connected with the contact difference of potential between the
metal contaminated by gases and the pure metal. A relation
between the constants A and b for the positive emission, such
as is contained in the data above, would be expected to arise,
in the same way as for the negative, If the positive ions were
present in the metal and if their internal concentration were
independent of the nature and pressure of the gas and of other
external factors. The theory of the emission of these posi-
tive ions would then be similar to that of the emission of the
negative electrons. The main differences would result from
the atomic dimensions of the positive ions and their much
smaller concentration In the metal. The effect of gases on the
positive emission would then be closely connected with the
corresponding contact potentials, although the effects might
not show an exact correspondence with those given by the
negative emission on account of the atomic character of the
positive ions. With the positive Ions there may be a material,
as well as an electrical, factor to consider, Several years ago
the writer^l pointed out that the phenomena which characterize

» " Phil Trans., A.," Vol. CCV11, p, 6x (1906),

16*



	EFFECT OF GASES ON POSITIVE IONS 243 in the following table. The values for the negative emission under similar conditions are added for comparison:—

	Oxygen Air Nitrogen Hydrogen Hydrogen	Pressure A / A i (mm,). -I- -I - - ss 7x10™ 1-52 x To⁴ 4xio^aft 678 x io⁴ 760 7 x io'^IH 2-46 x io⁴ lo'-'¹ 4-49 x io⁴ 28 4 x ro'ⁿ 3-56 x to⁴ 3 x ro^<J« 5*6 x io⁴ i'9 to^lt{ 170 x io⁴ J.o'^w 474 x jo⁴ 226 io'^t() ^-85 x xo⁴ 3 x io^ul 278 x io⁴

	It is a remarkable fact that the constants for the positive emission, in the table above, exhibit a linear relation between log A and b similar to that shown by the constants for the nega- tive emissions from platinum and tungsten, which was con- sidered in Chapter IV. Moreover, the constant a{c> or r, considered on p, 137, has a very similar value, being equal to 143 x io¹¹ for the positive emission from platinum in various gases, as compared with the values 3-29 x io^y for the nega- tive emission from platinum and 256 x io^:{ for the negative emission from tungsten. We have seen that, in the case of the negative emissions, the linear relation in question is closely connected with the contact difference of potential between the metal contaminated by gases and the pure metal. A relation between the constants A and b for the positive emission, such as is contained in the data above, would be expected to arise, in the same way as for the negative, If the positive ions were present in the metal and if their internal concentration were independent of the nature and pressure of the gas and of other external factors. The theory of the emission of these posi- tive ions would then be similar to that of the emission of the negative electrons. The main differences would result from the atomic dimensions of the positive ions and their much smaller concentration In the metal. The effect of gases on the positive emission would then be closely connected with the corresponding contact potentials, although the effects might not show an exact correspondence with those given by the negative emission on account of the atomic character of the positive ions. With the positive Ions there may be a material, as well as an electrical, factor to consider, Several years ago the writer^l pointed out that the phenomena which characterize » " Phil Trans., A.," Vol. CCV11, p, 6x (1906), 16*