582 



REPORT 1897. 



added to water in forming tlie solution, Wi = ]S', +N3, r?v, = N2 + N^, N3 = N^. 

 The solution of these equations, even by the aid of a graphical process, 

 seems to require more accurate values of the conductivity of simple solutions 

 than -we possess. But with the measurements available, we may readily prepare 

 a solution having any desired concentration of ions, and therefore having one of 

 the electrolytes present with any desired degree of ionisation. For this purpose 

 draw curves for simple solutions of 1, 2, 3, 4, giving the relation of concentration 

 of ions to dilution. Read oif from these curves the dilutions, Vj, V,, &c., of simple 

 solutions of 1, 2, 3, 4 respectively, having the desired common value of the con- 

 centration of ions. If simple solutions of these dilutions are mixed in proper pro- 

 portions as to volume, there will be no change of ionisation on mi.xing. To find 

 the proper proportions, select any arbitrary value, v^, of the volume of 4 which is 

 to be mixed with the others. It will contain N^ = y^/V^ grm.-equivalents of 4. 

 From equations (d) above we must have N3 = N4. Hence the volume of 3 to be 

 mixed with the others will be v^ = V3 w^/V^. Next select arbitrarily any value 



of v.y Then from the second of equations {a) we have v^ = v^ v^/'v.^ = V3 v^-yV^ v„. 

 The volumes of the simple solutions of dilutions Vj, V„, V,, 'V^, which must be 

 mixed, in order to form a complex solution having the desired concentration of 

 ions, are thus known. The solution may therefore be prepared. Moreover, as the 

 concentrations of the simple solutions and the volumes of them which are mixed 

 are known, the numbers of grm.-equivalents of the four electrolytes present may 

 be determined ; and as the common concentration of ions and the dilutions are 

 known, the ionisation coefficients may be determined. The conductivity of the 

 solution may therefore be calculated. 



That the values of the ionisation coefficients obtained in this way are those 

 demanded by the dissociation theory is borne out in this case also by the agree- 

 ment between the observed values of the conductivity of solutions of the kind 

 under consideration and the values calculated by the aid of these coefficients. 

 Mr. E. H. Archibald, working in my laboratory, has recently both observed (by 

 Kohlrausch's method) and calculated the conductivities of solutions containing 

 NaCl and KoSO^, and therefore also KCl and Na2S0J^. I am indebted to him for 

 the following statement of his results so far as he has gone : — 



These results go to show that the ionisation coefficients of the electrolytes in the 

 above solutions have been fairly accurately determined. They are interesting in 

 themselves also as showing that the dissociation theory enables us to calculate the 

 conductivity of a solution containing two electrolytes with no common ion. 



