4(56 Mil. S. CHAPMAN ON THE KINETIC THEORY OF A GAS 



4 Calculated from y. 



6 , ' Calculated from C p and y, as given in the Smithsonian tables. 



~ ZIEGLER, ' Halle Diss.,' 1904. STEFAN ('Wiener Sitz.,' 72, II., p. 69, 1875) had found & x 1<F= 780 

 for methane, and WINKELMANN ('Pooo. Ann.,' 156, p. 497, 1875) obtained the value 647. There are no 

 previous determinations for ethane. 



8 Determined by WINKELMANN, as given in the Smithsonian tables. 



9 WINKELMANN (MEYER, p. 295). 



10 SCHWARZE, loc. tit. ; WINKELMANN'S and MxJLLER's determinations have already been mentioned. 

 There are also experiments by TODD ('Roy. Soc. Proc.,' A, 1909, 83, p. 19) and ECKERLEIN ('Ann. d. 

 Phys.,' 3, p. 120, 1900), the latter being at low temperatures (for air, hydrogen, and carbon dioxide). 



11 Gii.NTHER, 'Halle Diss.,' 1906. Also see MEYER'S treatise for earlier determinations, 



The authorities for the above values of /j. a will be given later, when we come to 

 discuss the coefficient of viscosity. The table shows that the results agree neither 

 with MEYER'S nor BOLTZMANN'S theory. The values of f for methane and ammonia 

 stand out from the others, which show a tendency to increase with y ; as all the 

 values of f are less than f it would appear that the view of STEFAN and BOLTZMANN 

 is correct, that the atomic energy travels slower than the translational energy. 



In conclusion it may be remarked that the formula 3- =f/j.G v shows that 3- will 

 behave (as the temperature or pressure varies) in a way which can be predicted from 

 the behaviour of ft and C separately, if the equation is correct. Experiments have 

 confirmed this, and we shall therefore leave the discussion of these laws till we come 

 to the simpler case of fj. itself. 



18. The Coefficient of Conduction for a Mixed Gas. 



The expression we have obtained for this quantity enables us to determine it in 

 terms of the coefficients of viscosity of the two pure gases forming the mixture, and of 

 their coefficient of diffusion, provided that we know the law of interaction between 

 the molecules. The latter is involved in the constants k, k lt and k 2 , but these do not 

 vary very much with the law of force. In Part II. of this paper we have determined 

 their values in some special cases as follows : - 



Rigid elastic spheres (46) 



k 1, a 5> k% = f 5> 

 MAXWELL'S repelling molecules (48 and 49) 



k = 0771, k, = 1, k, = I, 

 Attracting rigid spheres (52) 



7. _i + ic/e * A8 



' 



where (as we shall see in 21) the constant C 13 must be determined by experiments 



