| 
rs } 
2 Messrs Paine and Evans, The Conductiwity of | 
constituents taken separately. This will go on until all the) 
impurity has been neutralised, as it were; we should then expect 
normal behaviour on the part of subsequent additions of H,SO,. — 
Accordingly, if we plot the simple conductivity (instead of the 
equivalent conductivity) of the dilute acid solution (after sub- 
tracting the conductivity of the solvent) against the concentration, | 
we shall obtain a straight line for the region of normal behaviour, 
(if the ionisation of the acid be complete). If this straight line’ 
be produced, it will cut the conductivity axis below the origin at) 
a point corresponding to the loss of conductivity involved in the) 
association of ions described above. * —__ 
Whetham and Paine have already shown that this is the case’ 
for sulphuric acid solutions. The present authors have tested the) 
rule with data supplied by Kohlrausch* and Whethamy+. The 
straight line of Fig. 1, for example, is derived from Kohlrausch’s 
i a 
7 
Atl = 
Conductivity (10-4 reciprocal ohm) 
1 2 3 
Concentration of H,SO, (10-4 gm.-equiv. per litre) 
Fig. 1. 
results. The experimental points lie accurately in a straight line 
for. concentrations ranging from the concentration of Kohlrausch*: 
most dilute solution up to 6 x 10~ gm.-equivalent per litre (the: 
neighbourhood of the maximum in the ‘equivalent’ conductivity, 
curve for sulphuric acid). For greater concentrations of sulphuric 
acid, of course, the ionisation cannot be regarded as complete. _ 
~ It may be remarked that the simple conductivity curve of a 
* See Whetham, Theory of Solutions, p. 437. ~ 
+ Phil. Trans., a. 194 (1900), p. 343. 
