85 



VISCOSITY OF GASES 



Carbonic Acid. 



221 



After this excellent agreement between observation and 

 calculation, we can scarcely doubt the correctness of the 

 explanation given by Sutherland. We may therefore 

 find room here also for the values of the constant of co- 

 hesion which Sutherland has deduced from von Ober- 

 mayer's 1 observations. 



N 2 Nitrogen 



2 Oxygen 



CO Carbon monoxide 



N 2 Nitrous oxide 



C 2 H 4 Ethylene . 



C = 



84 

 127 

 100 

 260 



272 



86. Viscosity of Vapours 



Of the observations hitherto carried out many refer to 

 gases which would more properly be termed vapours, since 

 they can be changed into liquids by a simple increment of 

 pressure. To this category belongs even that gas, the 

 viscosity of which has been investigated by many observers 

 with especial care, viz. carbonic acid. 



This example is quite sufficient to prove the right of 

 those substances to be denoted as gases. But the true basis 

 of this right lies in the fact that the vapours have been 

 examined as to their viscosity in circumstances under 

 which they satisfy the laws of perfect gases with sufficient 



1 Wiener Sitzungsber. 1876, Ixxiii. Abth. 2, p. 433 ; Carl's Repert. 1877, 

 xiii. p. 130. 



