697 



3 5 ^^ 



— Rln 2jr + — R. ^) This value of 6, amounts successively to 3,5677ï*, 



4,257 B and 5,257 R. 



The values given by Sackur and Tetrodk for di-atomic gases, are : 



5 5 7 3 



iy„=i =^-RlnT + -RbiR RlnN ^-Rhim — 



2 2 2 ^2 



9 7 



~ ^ R bi h -{- R In M -\- - Rln 2 + ~ R In n. ^ C ^ , . . (2) 



5 

 in which C\ accordijig to Sackur amounts to — R , according to 



7 „ 

 Tetrode to — R. 



We get for a tri-atoraic gas : 



3 

 Hn=\ = SRhiT -{- ?> RhiR - ARln N -{- -R In m — 



— QR In h + -R In M.MJf, H 6 Rln 2 i- 'o Rbijr ^- C, , . . (3) 



in which C^ amounts to 3 /? according to Sackur, to 4 7? according 

 to Tetrode. 



Besides the known values N and h, the moments of inertia of 

 the molecules occur therefore in these expressions. For the di-atomic 

 molecules M is the moment of inertia of the dumbbell shaped mole- 

 cule with respect to an axis through the centre of gravitj^ normal 

 to Ihe bar of the dumbbell; for the tri-atomic molecules J/ijilYj and 

 Mg are the three chief moments of inertia, which accordingly depend 

 on the relative position of the three atoms in the molecule. 



For equilibria in which only mon- or di-atomic molecules parti- 

 cipate, the moments of inertia of the diatomic particles therefore 

 occur, which can be approximately calculated from the ditferent 

 determinations of the mean molecule radius. For a test of the 

 formulae by equilibria of tri-atomic molecules, however, a hypothesis 

 concerning the relative situation of the atoms is indispensable, which 

 is more or less arbitrary, and can make the test less convincing. 



3. The equilibrium AB'^A-\-B. 



For the simplest gas equilibrium AB"^ A -\- B, in which the 

 atoms A and B can be of the same or of dilFerent kinds, we 



^) In tlie expressions of Tetrode 1. c. the terms with s are omitted, which 

 seems justified. 



46* 



