636 
Proceedings of the Royal Society of Edinburgh. [Sess. 
chlorates, bromates, and iodates of the alkalies and some salts of the 
alkaline earths. The concentration of the solutions is expressed in 
terms of gram-molecules salt dissolved in 1000 grams of water. We 
express by w the weight of m gram -molecules of the salt, and the total 
weight of the solution by W = (^ + 1000) grams. The specific gravity of 
solution, S, is referred to that of distilled water at the same temperature 
(T), as unity. In the majority of cases T = 195° C., but in some cases 
T = 15° C., and in others T = 23° C. 
In the solutions of any particular salt, for which the general symbol 
used is MR, the values of m, representing the amount of salt expressed in 
gram-molecules dissolved in 1000 grams water, are in a descending 
geometrical series, beginning usually with m = J and proceeding m — \, -J, 
down to, in most cases, and in some yp 2 4 ? a gram-molecule. 
The results obtained are set forth in various tabular forms. In the 
first twenty-four tables, class A, the specific gravity, S, of each solution is the 
mean of several series of observations made with two. different hydrometers, 
generally Nos. 17 and 21. The facts of observation which are entered in 
these tables are: — under m the quantity of salt, in terms of the gram-molecule, 
dissolved in 1000 grams of water ; under W the weight, in grams, of this 
solution ; and under S the specific gravity of the solution at the temperature 
T referred to that of distilled water of the same temperature as unity. 
These are the observed data, and the first derived datum, namely, that of 
the Displacement , A = W/S of the solution, is given. It is expressed as the 
weight in grams of distilled water having the temperature T which is 
displaced by, or has the same volume as, the weight W of the solution, having 
also the temperature T. The advantage of using the term “ displacement ” 
in preference to “ volume ” is that a weight is never thought of as a function 
of temperature, whereas a volume is always so regarded. In our experi- 
ments the temperature is a constant. 
On page 637 is given an example of a table in class A. It is Table No. 1 
referring to solutions of m KC1 + 1000 grams water at 19*5° C. There are 
nine concentrations, m = J to inclusive. The two columns of differences, 
dA and d lo£ A, are omitted. 
In this research all the weights given represent weights in vacuo. The 
values under m and W represent direct weighings on delicate balances with 
standard weights. The exactness of the values under S form the subject of 
a table of series B for each table of series A in which two hydrometers 
were used. An example is given on page 637. 
