226 RELATION OF PHYSICAL PROPERTIES OF AQUEOUS SOLUTIONS 
to only the first five of the above observations. To represent 
the viscosity of stronger solutions he had to introduce a term 
expressing the effect due to the mutual action of the molecules 
of salt—kKCl. All six observations were used. The agreement 
in this case is quite satisfactory. 
Surface-Tension.— NaCl. Only two observations on suffi- 
ciently dilute solutions were available, and the applicability of 
the formula cannot therefore be tested. The constants were 
found, for use in the calculation of the surface-tension of 
mixtures.—KCl. The first four ohservations were used, and the 
agreement is quite satisfactory up to a concentration of 3 grm,- 
mols. per litre. 
Refractive Index.—In the ease of both salts the first three 
observations were used, and in both the agreement is quite satis- 
factory up to a concentration of about 2 grm.-mols. per litre. 
The above tables seem to be at any rate quite 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 lonization-constants used in the above 
calculations :— 
| 
SODIUM CHLORIDE. POTASSIUM CHLORIDE. 
k. Ul k. if 
Density, Sesto se tee + 030841 + °045079 + °03543 + 048591 
Thermal Expansion.| — ‘0001445 | + :C007658 — ‘000614 | +°00069685 
Viscosity, 25...525%5 + ‘002847 + 0001504 + 001904 | —-*0009247 
Surface-Tension....| +°20574 + 11001 + *24249 + °126806 
Refractive Index... + 006318 + 011713 + ‘0027853 | + °011853 
