Section III, 1919 [177J Trans. R.S.C. 



The Variation of the Coefficient of Viscosity of Gases with J emperature 



{Abstract). 



By Robert Clark, B.A. 



Presented by Dr. Louis V. King, F. R.S.C. 



(Read May Meeting, 1919.) 



It was suggested to the writer by Dr. L. V. King, that it would be 

 desirable, with a view to the further development of the Dynamical 

 Theory of Gases, to measure the variation of the viscosities of the 

 principal gases over as extensive a range of temperature as possible. 

 The experiments described were undertaken to ascertain the possi- 

 bilities of a comparative method of determining this variation. 



The coefficient of viscosity of air has been very accurately deter- 

 mined by Millikan for the temperature 23.0° C- and it was evident 

 that this value might be employed to calibrate a capillary tube, with- 

 out resorting to a careful calibration by means of a mercury thread, 

 an operation which is somewhat difficult and always more or less 

 uncertain. Further as it is intended to extend the investigation to 

 the highest temperature at which fused silica will remain gas-tight 

 and as the difficulty of maintaining a uniform high temperature 

 increases very rapidly with the size of the furnace the apparatus was 

 made as small as possible consistent with the accuracy that was 

 desired. 



The present paper is an account of an investigation undertaken 

 to test this type of apparatus. It will be seen below that the 

 method is feasible. A larger apparatus has been constructed which 

 should give fairly accurate results over a range of about 200° C, and 

 it is hoped in the near future to construct an apparatus in fused silica 

 and measure viscosities at temperatures up to 600° C. 



If two vessels of known volumes, be connected by a capillary tube, 

 any pressure difference between them will gradually disappear, in 

 consequence of flow through the capillary. This flow can be calcu- 

 lated in terms of the rate of change in pressure difference, and the 

 volumes of the two vessels; from the dimensions of the capillary tube 

 the coefficient of viscosity may be determined. If the rate of change 

 of pressure be observed when the apparatus is maintained at different 

 temperatures, the values of the coefficient of viscosity corresponding 

 to these temperatures may be obtained. 



^Millikan, R. A., The Electron, Chicago 1917, p. 92. 



