32 
PROFESSOR W. A. TILDEN AND MR. W. A. SHENSTONE ON THE 
two sets of figures are nearly parallel. Hence we think it possible that the salt used 
by Gay Lussac may have been slightly acid. On the other hand, our own results 
at temperatures above 120° may be somewhat too low. 
Copper sulphate. 
Temperature. 
Parts of CuS0 4 in 100 parts 
of water. 
120 
90-1 
135 
85-5 
140 
84-4 
157 
82-0 
188 
74-5 
These results are of do value as showing the solubility of the salt, for at tem¬ 
peratures above 120° chemical action ensues, with production of a green basic sulphate. 
And even at 120° there is reason to suppose that decomposition has commenced, 
inasmuch as 90 d is below the solubility that would be inferred from a consideration 
of the solubilities (see Poggiale, Ann. Chim. Phys. [3], viii., 467) determined at 
lower temperatures. 
Sodtum chloride.—Melting point 772°. 
Temperature. 
Parts of salt in 100 parts 
of water. 
0 
118 
140 
160 
180 
39-S'l , 
42’1 ex P- maf ’- e 
43- 6 r in the 
44- 9 J metal tube - 
(See Plate 2). 
Reference to the curve shows that the solubility increases at temperatures above 
100° faster than below. 
Potassium chloride.—Melting point 734°. 
Temperature. 
Parts of salt in 100 parts 
of water. 
0 
125 
59'6 in metal tube. 
133 
144 
175 
69 3 ) • , 
70'8 l m §1 ass 
75-2 j tube - 
180 
77'5 in metal tube. 
