142 Proceedings of Royal Society of Edinburgh. [sess. 
weight per square inch (152'3 atmospheres) is the pressure unit, 
s is nearly the weight of salt in 100 of water. 
Theoretical speculations (given at some length in my Report on 
some of the Physical Properties of Water, Challenger Reports, 
Physics and Chemistry, vol. ii., 1888) led me to look on the B, 
and the B + s, of these formulae as being connected with the 
molecular pressure in the liquid, and I developed one application of 
them, relating to the maximum density points of various solutions 
of common salt. 
The present series of experiments was conducted precisely as were 
the earlier ones, but unfortunately many of the piezometers (of 
which a large number were required in order that several solutions 
should be operated on at the same time) were new, and (as I after- 
wards found) faulty. The selection of the salts was undertaken by 
Dr Crum Brown, and the solutions were made and the density 
determinations effected in his Laboratory by Mr A. F. Watson. 
I give these at once, as they have intrinsic value altogether apart 
from my work and my hypothesis. 
In the following table the letters S and W stand for the masses 
of salt, and of water, respectively. Mr Watson remarks that the 
error in the numbers of the first column, from which the second was 
calculated, does not exceed 1 in 1000. The error in the densities 
does not exceed unit in the fourth decimal place. 
^^^8+ W 
o 
o 
Temp. 
C. 
^p. Gr. 
Temp. 
C. 
Sp. Gr. 
Potassium Iodide — 
14-538 
17-011 
5°-5 
1-1197 
13°-5 
1-1179 
9-302 
10-25G 
5°-6 
1-0737 
12°-2 
1-0727 
4-313 
4-507 
5°-4 
1-0329 
12°-0 
1-0323 
Potassium Ferrocyanide- 
14-089 
16-399 
5°-5 
1-0987 
13°-5 
1-0967 
9-411 
10-389 
6°-3 
1-0620 
12°-1 
1-0610 
4-753 
4-990 
6°-0 
1-0328 
ll°-4 
1-0322 
Ammonium Sulphate — 
15-938 
18-960 
6°-8 
1-0954 
ll°-2 
1-0944 
9-232 
10-171 
6°-3 
1-0559 
12°-7 
1-0547 
5-301 
5-597 
5°-7 
1-0326 
12°-1 
1-0317 
