Effusion of Argon, Helium, and some other Gases. 437 



Argon* 



Carbon monoxide ... 

 Carbon dioxide 



m. s. 



12 3-9 



10 30 



13 2 



m. s. 



12 31-2 



10 32-9 



13 154 



in. s. 



12 31 



10 32-3 



13 11 



per cent. 

 36 



i 



0-36 



« 1 



The first column gives the observed time, the second the 

 time calculated from the densities alone, the third the calculated 

 time corrected for viscosity, and the fourth the percentage 

 deviation of the observed time from the time so corrected. In 

 the case of argon and carbon monoxide the correction is quite 

 negligible. For C0 2 it amounts only to *5 per cent. The 

 conclusions previously drawn remain therefore unaffected. 



With regard to C0 2 , the want of agreement between theory 

 and experiment may possibly be due to the fact that this gas 

 departs too much from the simple laws of the ideal gas. 



In the case of argon the time of effusion, as calculated from 

 that of oxygen according to the theory given by Hugoniot 

 and Osborne Reynolds, is ll m 55 s f. It is only to be expected 

 that the observed value would be greater, as the phenomenon 

 is probably something intermediate between isothermal and 

 adiabatic J . 



* The viscosity of argon referred to oxygen was obtained by com- 

 bining Lord Rayleigh's value referred to air with Graham's value of 

 air referred to oxygen. The result is 1*21 X *901 = 1 , 09. 



f According to Parenty's formula, it is 11^ 31s-7. 



% A few words of explanation are necessaiy here. In the first place, 

 the mass-efflux on the assumption that the phenomenon is isothermal 



$ 



may be found as follows : — Employing the equation | -^- +^'- = const. 

 which holds along a stream-line for steady irrotational motion, we obtain 

 on integrating, since p= P UT, q = a/ 2RT log - , where p = density of 



quiescent gas in the reservoir. If the velocity, density, and sectional 

 area at the vena contracta be denoted by q', p' , and S' respectively, then 



mass-efflux =q'p'S ! . From the condition -r- (qp) = 0, we find logQ =§ 



and therefore S'q'p' = - , =- . Thus comparing two gases between the 



i-y/i 



VeKT* 



same pressure-limits during the period of constant efflux, t 1 = 

 as already stated. 



The equation given by Parenty being based neither on the assumption 

 of an adiabatic nor an isothermal efflux, and being in fact practically an 

 empirical equation, not much importance need be attached to the' fact 

 that it yields a value which is very sensibly smaller than that observed. 



It must be noted that on the assumption of constant temperature, the 

 velocity of the gas at the vena contracta is less than the velocity of sound 

 in gas of that density aud pressure, being in fact equal to the Newtonian 

 value. 



