259 
/ 4 
— art’ 
molecule has been placed there is a volume dv, }1 — 5 | left 
vj 
available for the second of the mq single molecules. The second mole- 
4 
— nv 
cule, therefore, gives rise to the factor x Ene oes in the num- 
Vv 
1 
ber of micro-complexions. The third of the 71, molecules gives x 
1 — craic ; In this no account is taken of the fact that in a 
‚U 
1 
number of micro-complexions the spheres of influence of the first two 
molecules partially overlap, as these complications need only be 
allowed for in the calculation of the C and subsequent virial-coeffi- 
cients (cf. $ 3). Proceeding in this fashion the 7, single molecules give 
the factor 
4 8 
5 tn, —1 Gere 
OS Glee sa awa 
== dv, 
We must now place the 7, molecules which belong to pairs whose 
distance apart lies between 7, and r, + dr,. In order to see in how 
many different ways this may be done we must first notice that one 
of these molecules can go to form a pair whose distance apart lies 
between the proper limits only in combination with another of the 
same group (this does not strictly hold if the molecule in question 
is placed on the boundaries of dv, ; if, is sufficiently great, however, 
the effect of this may be neglected). The ,, molecules can then 
combine to form pairs in 
different ways. Let us take one of these combinations. Take one of 
the pairs and place it; this is done by first assigning a place to one 
of the pair. As it must be placed outside the sphere of influence of 
any of the »,, single molecules already in position there are left 
+ 
— nt 
3 
* jl — ma —— 
v, 
places available. Having placed the first molecule of the pair in 
