Effusion of Argon, Itelium, and some other Gases. 441 



Argon. — Density 19*71. 



in. s. m. s. 

 Oxygen ... 8 24*2 

 Argon ... 9 0*6, 8 59*5 

 Oxygen ... 8 23*8 



m. s. 

 Mean time for argon (observed) ... 9 

 Calculated from densities alone . . . 9 19*4 

 „ with viscosity- correction . . 9 19*2 



These results show that in the case of argon the correction is 

 negligible and that the observed time is 3*4 per cent, less than 

 the calculated time, which is in good agreement with former 

 results. In the case of helium the viscosity correction is still 

 considerable and, contrary to previous results, the observed 

 and calculated values agree. 



After these measurements the times for oxygen and hydro- 

 gen were again determined : — 



m. s. m. s. 

 Oxygen . . 8 23*9 

 Hydrogen. . 2 6'6, 2 6'8 

 Oxygen . . 8 23*3 



The time for hydrogen calculated from the densities is 2 m 6 s, 4, 

 so that there now appeared to be practically no viscosity-effect. 

 Under these circumstances it appears difficult to say what 

 sort of correction ought to be applied to the last-obtained 

 results for helium. In order to try and clear up this diffi- 

 culty a fresh series of measurements was made, with the 

 following results : — 



Argon. — Pure specimen, density 19*96. 



m. s. 



Argon 9 1*4 



Mean oxygen 8 22*8 



Argon (from densities) . . . . 9 21*6 

 Argon (corrected for viscosity) . 9 21*4 



Observed rate 3*5 per cent, faster than calculated rate. 

 Helium. — Purer specimen, density 2*139. 



111. s. 



Oxygen .... 8 22*8 

 Helium .... 3 7*8 

 Oxygen .... 8 22*6 



111. s. 



Helium (calculated from densities) . . 3 3*8 

 Helium (with viscosity correction) . . 3 9*4 



