SOLUBILITY OF SALTS IN WATER AT HIGH TEMPERATURES. 
27 
in an adjustable cradle (Plate 1, fig. 2), which consists of a stout beam of wood, B, 
supported by a horizontal rod of iron which passes through o, and serves as a pivot on 
which the beam can turn. Attached to the upper side of this beam is an index, 
which moves against the face of a semicircle of wood S, fixed rigidly to the rod on 
which B turns. The index can be pinned to the semicircle at the holes h, h, h, h, 
so that the beam can be inclined to the horizontal at any desired angle. The cradle 
of sheet copper, C, is supported by the w 7 ires iv, u\ and in this the tube lies. 
The tube being in position in the cradle, with the end B slightly elevated, and the 
opening e in the screen downwards, the whole is lowered into a paraffin bath by 
lowering the rod which supports the beam, and which is itself fixed by an ordinary 
clamp to the upright of a large retort stand. After heating at a steady temperature 
for four-and-a-half or five hours, the end A of the tube is raised, and B depressed, very 
gradually, keeping the whole tube below the surface of the paraffin. When time has 
been allowed for the solution to drain away, the tube is turned half round its long 
axis by the handle h, so that the screen is interposed between the solution and the 
residual salt, and so liquid from the latter is prevented from continuing to drain 
into the former. The tube is then placed in a position more nearly horizontal, but 
still with the end A raised somewhat higher than B, which now contains the solution. 
The cradle, with the tube, is then lifted from the bath, and allowed to cool in the 
air. When cold it is opened, the disk is removed, and a stopper placed in the mouth 
of B. After cleansing the outside of the tube by washing in benzoline, the tube and 
solution are weighed. Then the solution, which is usually in a solid or semi-solid 
state, having been removed to a tared dish for analysis, the dry tube is finally 
reweighed. 
The capacity of B to the mouth was 16'4 cub. centims. 
The results given below with sodium sulphate show that the process yields very 
satisfactory results. It necessitates, however, a good deal of trouble, and each 
experiment occupies more than a day. 
In order that our results might be readily compared w 7 ith the determinations made 
by other experimenters at lower temperatures, we have added many of these latter 
to the tables. The numbers are taken from the several original sources, and have 
been recalculated to show the weight of salt in 100 parts of water when not so 
given in the memoir referred to. In the curves which accompany the tables the 
results of other experimenters are put in dotted lines. We have also added at the 
head of each table the melting point of the salt. For these we have adopted the 
values obtained by Professor T. Carnelley (Jour. Chem. Soc., 1876, i., 489 ; 
1878, i., 273), though in one or two cases, where data were not to be found, a rough 
determination of the melting point has been made by ourselves. 
