CONTRIBUTIONS FROM THE JEFFERSON PHYSICAL LABORATORY, 

 HARVARD UNIVERSITY. 



VISCOSITY OF AIR. 

 By J. L. IIoGG. 



Presented by John Trowbridge, December U, 1901. Received January 9, 1905. 



Fro.m the staudpoiiit of the Kinetic Theory of Gases the viscosity, 

 or iuternal friction, of a gas is a very important property, and, on this 

 account, it is not surprising that a determination of the coefficient of 

 viscosity of various gases has been the subject of investigation for many- 

 scientists. Air has been submitted to investigation probably more fre- 

 quently than any other gas, but although many careful experiments have 

 been performed and though the results of the more recent measurements 

 show much better agreement than the earlier results showed, yet there 

 is still some lack of agreement in the results obtained by different inves- 

 tigators using the same method as well as in those obtained by different 

 methods. For example, 0. E. Meyer * using one method obtained re- 

 sults ranging from 0.000168 to 0.000174 for the value of the coefficient 

 of viscosity at 0° C. Breitenbach,t using the same method, got 0.0001 733, 

 which is in good agreement with the result obtained by Schultze | and 

 also with that obtained by Markowski. § By the same method, how- 

 ever, Schneebeli li obtained 0.0001707 and Obermeyer 1[ 0.0001705. 

 Tomlinson,** using a method involving another principle, obtained as 

 a mean result 0.0001715, while F. G. Reynolds,tt by the same general 

 method, obtained 0.0001767. 



Since experiments on the relation of viscosity to temperature show 

 a comparatively slow change in viscosity with clianging temperatuie, 

 and since the temperature of the gas is the only property of it which is 

 likely to be subject to even moderate change daring the course of an 

 experiment, it would seem that it should be possible to determine the 



* Pogg. Ann., cxlviii. t Ann. der Phys., 5, I'JOl. 



t Ann. der Pliys., 5, 1901. § Ann. der Pliys., 9, 1904. 



II Arch. Sci. Pliys. et Nat., 14, 1885. t Wiener Sitzungsber. Abth., 2, 1875. 



** Phil. Trans., 177, 1886. tt Pliys. Rev., July, 1904. 



