699 





NkT RT rio N 



Equation (5) can, therefore be written in the following form : 



lnKc = -±=^J^-ln T-lnM^lnll-e JcT\ + in C,, . (6) 



in which 



3 rriAmu 1 1 



InC, = -In ln2Nh -f - In k — ~ In 2nr . . (Cai 



^ 2 mA+mB 2 2 ^ ^ 



Equation (6) differs from equation (4) in this that in (6) the term 

 with V occurs, which takes a vibration of the two atoms in the 

 molecule into account; equation (6^7) quite agrees with (4(7). if in 

 the latter Tetrode's value is substituted; Sackur's value yields a 

 unity difference. 



5. The equilihriiun ./, ^ 2J . 



In the chemical literature a series of accurate observations occur 

 of Starck and Bodenstein ^) ; the dissociation constant of iodium 

 is given by them in concentrations, i.e. gram molecules per litre. 

 The equations (4) and (4^), resp. (6) and [Qa) yield for their disso- 

 ciation constant : 



Inil-e kr\\j^U,C,, (7) 



In KsB = -^-^=- + - In T—ln M + 



RT ^ 2 ^ 



in which log C^ = log C\ -\- 3 (according to Tetrode and v. d. Waals Jr.); 



log Cg = log C^ -\- 2,566 (according to Sackur). 



Making use of the values: iV = 6.85 10^'. (Perrin), /(,== 1.2110-16, 



127 

 A = 5.88 10— 27 ^„ _-^^^ __ ^yg pjj^^j 



6.85 1023 

 ^og Cg = — 36.313 (according to Tetrode and van der Waals Jr) 



— 36.747 (according to Sackur) (7a) 



In equation (7) there occur two (resp. three) quantities, which can 

 be calculated from the observations : 2?i Et—q, M (and v). 



As the term with v can only have slight influence on the result, 

 we write equation (7) as follows: 



2n Etz= , , , ^ 1 '~ ' ' ^ -^ 



+ logM=—logKsB + - % T + 



log[ 1— < 



kT 



2.303 i2T •" ^ -.. , 2 



— 36.313 (resp. — 36.747) . . (8) 

 Let us now assume that -?. remains below 20f/, which seems justified 



1) Zeitschr. f. Elektrochem. 16, 961 (1910). 



