510 Prof. J. G. MacGregor on a Diagram of 



Deguisne's* observations on the variation of conductivity 

 with temperature between 2° C. and 34° have enabled me, by 

 the method just mentioned, to make rough determinations of 

 the ionization-coefficients at 0° in some cases, on the assump- 

 tion that his empirical constants might be used down to 0°. 

 AccordiDg to Deguisne's observations the ratio of the conduc- 

 tivities at 0° and 18° usually changes gradually down to 

 dilutions of 1000 litres per gramme-equivalent, and between 

 that and 2000 undergoes rapid change. As observations at 

 great dilution are attended by considerable difficulty, I have 

 assumed that these sudden changes were probably due to 

 errors of observation. If they were not, my Deguisne 

 coefficients (for which Deguisne himself is of course not to be 

 held responsible) may be considerably out. 



In some cases I have obtained coefficients from the above 

 data by extrapolation, in order to make use of available 

 depression data. In such cases I have plotted side by side 

 ionization-coefficient-concentration curves for both 0° and 18°, 

 using values for 18° based on Kohlrausch's conductivities, 

 and I have then produced the 0° curve beyond the limit of 

 observation under the guidance of the 18° curve. 



I need not give here the values of the coefficients used in 

 the diagram. They will be found in the paper f of which 

 this is an abstract, and have been fairly accurately embodied 

 in the accompanying diagram (Plate IV.). 



I have used all the accessible observations of depression for 

 the electrolytes for which data were available as to ionization 

 at 0°, including observations by ArrheniusJ, Raoult§, 

 Loomis||, Joneslf, Abegg**, Wildermann ft, Ponsot %%, Archi- 

 bald § § , and Barnes § § . The methods used by these observers 

 are for the most part well known. Archibald and Barnes 

 used modified forms of LoonnVs method. Arrhenius's 

 obsei vations and some of Raoult's were made before important 



* Temperatur- Coefficienten des Leitvermb'gens sehr verdiinnter Losungen : 

 Dissertation, Strassburg, 1895 ; see also Kohlrausch u. Holborn, Leitver- 

 mbgen d. JElektrolyte, Leipzig, 1898. 



f Trans. N. S. Inst. Sci. vol. x. Part 2 (not yet published). 

 % Zschr.f.phys. Ckem. ii. 491 (1888). 

 s Ibid. ii. p. 501 (1888) ; and xxvii. p. 617 (1898). 

 || Phys. Review, i. pp. 199 & 274 (1893-4) ; iii. p. 270 (1896) ; and iv. 

 p. 273 (1897). 



51 Zschr. f phys. Chem. xi. pp. 110 & 529 (1893) ; and xii. p. 623 (1893). 

 ** Ibid. xx. p. 207 (1896). 

 ft Ibid. xix. p. 233 (1896). 



XX Recherches sur la Congelation des Solutions Aqueuses: Paris, 

 Gautbier-Villars (1896). 

 §§ Loc. cit. 



