52 Prof. J. Gr. MacGregor on the Belation of the Physical 



and the agreement is quite satisfactory up to a concentration 

 of 3 grm.-mols. per litre. 



Refractive Index. — In the case of both salts the first three 

 observations were used, and in Loth the agreement is quite 

 satisfactory up to a concentration of about 2 grm.-mols. 

 per litre. 



The above tables seem to be at any rate qnite consistent 

 with the possibility of expressing the values of at least five 

 of the physical properties of moderately dilute solutions in 

 terms of their state of ionization. I hope to find leisure at an 

 early date to extend the investigation to solutions of salts and 

 acids of a more complex character and to other properties. 



The following are the ionization-constants used in the 

 above calculations : — 





Sodium Chloride. 



Potassium Chloride. 



k. 



I, 



7c. 



I. 



Density 



Thermal Expansion 

 Viscosity 



+•030841 

 -•0001445 

 + •002347 

 + •20574 

 + •006318 



+ •045079 

 + •0007658 

 + •0001504 

 + 11001 

 + •011713 



+ •03543 

 -•000614 

 + •001904 

 +•24249 

 +•0027853 



+ 048591 

 + 00069685 

 -•0009247 

 + •126806 

 ■4- -011853 



Surface-Tension ... 

 Refractive Index . . . 



These constants are obtained from solutions of too great 

 concentration to be regarded as exact values. Nevertheless 

 it may be admissible so far as these two salts are concerned 

 to draw the following conclusions : — Undissociated and dis- 

 sociated molecules are nearly equally effective in increasing 

 the density, those dissociated, however, being somewhat the 

 more effective of the two. (2) Undissociated molecules 

 diminish the thermal expansion, those dissociated increasing 

 it to a greater extent. (3) In the case of viscosity it is the 

 undissociated molecules which have the preponderating 

 influence, those dissociated having but a slight effect, which 

 may be an increasing or a diminishing effect. Thus Arrhenius's 

 expectation that all dissociated ions would be found to diminish 

 viscosity seems to be only partially realized, though possibly 

 from observations on more dilute solutions, both Z's might be 

 found to be negative. (4) In the increase of surface-tension 

 the undissociated molecules have about twice as great an 

 influence as the dissociated, (5) In increasing the refractive 

 index it is the dissociated molecules which have the pre- 



