TRANSACTIONS OF SECTION A. 581 



In all the experiments the gases used were hut slightly ahove atmospheric 

 pressure. Owing to limited time, the author is not ahle to furnish further data. 

 Experiments to determine the many interesting questions involved are being 

 conducted. 



Mr. C. E. Timmerman, of Cornell University, has assisted the author in carry- 

 ing out the experiments. 



12. On the Determination of the State of lonisation in Dilute Aqueous 

 Solutions containing tioo Electrolytes. By Professor J. G. MacGregor, 

 D.Sc, Dalhousie College^ Halifax, N.S. 



The object of this communication is to draw attention to the possibility of 

 determining, in some cases, what, according to the dissociation conception of 

 electrolytic conduction, the coefficients of ionisation must be in the case of two 

 electrolytes present in the same solution, the electrolytes either having, or not 

 having, one ion in common, but being such as undergo no chemical change other 

 than double decomposition. 



When the two electrolytes (1 and 2) have one ion in common, they are the 

 only electrolytes present in the solution. For determining the lonisation co- 

 efficients (a„ a„) we have then the following equations ^ : — (a) a^/^i = Oo/V^, 

 where Vj, V„ are the regional dilutions of 1 and 2, i.e. the quotients of the volumes 

 of the regions of the solution which may be imagined to be occupied by 1 and 2 

 respectively, by the numbers Nj and N^ of gramme-equivalents of these electro- 

 lytes present, the equation being obtained from the conditions of kinetic equili- 

 brium ; {b) Nj Vi + N„ ¥2 = 1', obtained from the equality of the volume (v) of the 

 solution to the sum of the volumes of the regions referred to ; (c) aj/Vi =/i (Vj) 

 and a^/Vn =/; (V„), the functions/, and/^ being determined by means of measure- 

 ments of the conductivity of simple solutions, the concentrations of ions in the 

 regions occupied by the respective electrolytes being assumed to be the same as 

 they would be in simple solutions of the same dilution. A mode of solving these 

 equations by a graphical process is described in the papers cited above. 



That the values of the lonisation coefficients obtained by solving these equations 

 are those which the dissociation theory demands is borne out by the fact that, 

 in the case of solutions containing NaCl and KCl (see papers cited above) or NaOl 

 and^ HCl, when these values are substituted in the expression of the dissocia- 

 tion theory for the conductivity of a complex solution, the calculated values agree 

 with those observed within a fraction of 1 per cent. 



The following results of the observations made on the above solutions, with 

 respect to the relation of the lonisation in such solutions to the concentration, may 

 be stated:— (1) In the case of dilute solutions (containing no more than about 0-5 

 grm.-equiv. per litre of either electrolyte), the rate at which the common concen- 

 tration of ions increases with the concentration of either electrolyte is practically 

 constant ; (2) for solutions of greater concentration, this rate diminishes as the 

 concentration of the solution with respect to either electrolyte increases. 



When the electrolytes, 1 and 2, added to water in forming the solution, have 

 no common ion, other two, 3 and 4, are formed by double decomposition, and there 

 are thus four present in the solution. For determining the lonisation coefficients, 

 we have then the following equations ^ : — (a) ai/V, = a^XY.^ — "3/^3 = "i/^^f 

 and NiVj'NjV„ = N3V3-N.,V4, obtained from the conditions of equilibrium; 

 (6) N,V, + N2V;+ N3V3 + N4V4 = w, from the volume relation; (c) a,XY,= 

 /; (Vj)j Oj/Vj =_/■„(¥„), &c., from the relation of concentration of ions to dilu- 

 tion, the V's having the same signification as above; and (d) from the conser- 

 vation of mass, ??i and n^ being the numbers of grm.-equivalents of 1 and 2 



' Trans. N.S. Tiist. Sci., 9, 101 ; Phil. Mag. [5], 41, 27(5 (1896). 



■ Mcintosh, Trans. N.S. Inst. Sci., 9, 120 ; Phil. Mag. [5], 41, 510 (1896). 



' Trans. Eoy. Soc. Can. [2], 2, Sec. III. 65 (1896). 



