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II. On the Solubility of Salts in Water at High Temperatures. 
By William A. Tilden, D.Sc. Bond., F.R.S.; Professor of Chemistry in the Mason 
Science College, Birmingham, and W. A. Seenstone, F.I.C., F.C.S., 
Lecturer on Chemistry in Clifton College, Bristol. 
Received June 19,—Read June 21, 1883. 
[Plates 1, 2.] 
The experiments of which an account is given in the following paper originated in a 
desire to investigate further the remarkable anomalies which have been observed in 
the solubility of sulphate of sodium in water. It appears to have been first discovered 
by Gay Lussac (Ann. Chim. Phys., xi., 313) that whilst the solubility of this salt in 
water increases rapidly with rise of temperature above zero, it attains a maximum at 
33° or thereabouts, and above that temperature diminishes till the boiling point (about 
103°) of the saturated solution is reached. 
On referring, however, to the curve of solubility for this salt traced by Gay Lussac, 
or to the numbers published many years afterwards by Lowel (Ann. Chim. Phys. [3], 
xlix., 32), it will be seen that the rate of decrease of solubility, though at first rapid, 
soon slackens, and the descending curve becomes nearly parallel with the axis of the 
abscissas representing temperatures. It appeared probable that if the solubility of 
sulphate of sodium could be traced through a range of higher temperatures, the 
solubility would be found once more to increase, and the curve resume an upward 
direction. 
It was not possible, however, to undertake the investigation of an isolated case of 
this kind without extending the inquiry to the phenomena of solution in general, 
and we have thus been led to consider several questions, which were not immediately 
involved in the subject of our first experiments. One important point which our 
experiments illustrate is the relation, hitherto assumed I’ather than determined, 
between fusibility and solubility. 
In our earlier experiments the ordinary crystallised sulphate of sodium containing 
ten molecules of water of crystallisation was enclosed together with a suitable 
quantity of water in glass tubes, either bent in the middle to an angle of 130 -140°, 
or straight and divided midway by a strainer of fine platinum wire gauze. 
In either case the materials were placed at one end of the tube, which was held 
in an inclined position within an air bath, with double walls, and provided with a 
