382 
the outer wall of the capillary is even glowing hot. Also in view 
of the estimations of other observers, it cannot be considered much 
too high, when we put the “mean temperature” of the gas at e.g. 
Tavs = 3000°. Although with constant density the free length of path 
must be considered independent of the gas pressure (comp. e.g. 
L. BotrzMann’)), it should be borne in mind on the other hand 
that in our experiments as a consequence of the higher temperature 
of the gas in the capillary, the density of the gas present there is 
a fraction of that which the gas would possess at the pressure 
indicated by the manometer at room temperature. 
If eg. for p=0.087 mm. the value of 2 at room temperature 
would already lie below the above indicated limit determined by 
Lanemuir, under the circumstances of the high gas-temperature in the 
capillary this is not the case; i.e. for almost all the measured pres- 
sure-effects (cf. diss.) the conditions of the experiment have always 
been so that 2 had a sufficient value in comparison with the capillary 
diameter to enable us to apply the diffusion formulae that refer to 
highly rarefied gases (on the assumption that the electric state of 
the gas does not influence the diffusion laws). 
When M. Kyupsen’s theory?) is accepted, the velocity of transfusion 
q of a gas per second measured at a pressure of 1 barye through 
a tube under circumstances in which À is large with respect to the 
diameter D of the tube is, aecording to Irvine LaNGMuIR®), determined by: 
4h 8 
VERE al - 2s) 
(in which M/ == mol. weight p, —p, the difference of pressure, and L the 
length of the capillary). When À is small with respeet to D, the formula 
II D'p 
9 = 198 yp (PsP) - 2. + 3s 
q, = 3809 
must be taken, in which also g, is based on a volume measurement at a 
pressure of 1 barye and 7 represents the coefficient of friction of the gas: 
If we wanted to apply formula (2) to our observations, we should 
at least have to fill in the value of 4 for high temperatures. 
For simplicity’s sake, however, we fill in the value of 4 for air 
at room temperature, viz. 181.10-° C.G.S. units. Further on we 
shall state results which enable us to make our choice between 
equations 1 and 2. Then formula 2) becomes: 
4 
D 
7; = 136 Ti -?p pop.) . 5 - A . 5 . (3) 
1) Vorlesungen über Gastheorie 1910 p. 70—71, footnote. 
2) Ann. d. Phys. (4) 28, 76 and 999 (1909). 
3) Gen. Electr. Rev. 19, 1063 (1916). 
