NATURE OF SOLUTION. 605 
NOE 
a p Na,S,0, a a (Schonfeld) 
10-1 756°2 25°6 2°8741 2°59 
11:2 24:3 2°7267 2°53 
11:3 24:05 2°7001 2°54 
13°7 22°35 25079 2°42 
af 18-2 2:0422 2°21 
32:1 14:05 15766 1°67 
32°2 14°35 16111 1:66 
36°7 12°3 1:3802 1:48 
1 c.c.=0°0127 gm. iodine. 
These results are expressed in curves H,O (1), (2), and (3) of Diagram. It 
will be seen that these curves are not identical, but show a regular variation too 
great to be ascribed to experimental error. Experiment I. was begun when 
only a small quantity of chlorine hydrate had been formed ; in Experiment II. 
the water was allowed to become semi-solid before beginning the determina- 
tions ; Experiment III. was begun at 10° without formation of chlorine hydrate. 
The curves show that the solubility of chlorine in water, or at least the action 
on potassium iodide, is greater in proportion to the amount of chlorine hydrate 
previously formed. This applies only to the solubility after the decomposition 
of the hydrate, for several sets of determinations show that the solubility 
before the maximum point is reached is constant, and represented by the curve 
H,O (2), this part of curve H,O (1) being somewhat irregular on account of a 
circumstance mentioned above.“ An explanation may be found if it is supposed 
that hydrate of chlorine in decomposing forms a small quantity of hydrochloric 
or hypochlorous acid. The presence of hydrochloric acid would increase the 
solubility of chlorine in water (see p. 612). With a. view to ascertaining if 
hydrochloric acid is really formed, the reaction was tested after titration in a 
series of estimations made for another purpose (p. 603), and found to be neutral 
until the chlorine hydrate was decomposed, then distinctly acid. 
Curve H,O (Sch.) was drawn from ScHONFELD’s numbers, and it appears 
that the maximum as determined by him is too low, and indeed an initial rapid 
fall as seen in H,0 (3) is more probable than a gradual descent ; for it may be 
safely assumed that some chlorine hydrate is formed at 10°, but remains 
in solution. Its decomposition between 10° and 15° would produce the sudden 
descent. Ifthe temperature be reduced below 10° the hydrant crystallises out. 
The question then arises—Why does the remaining liquid dissolve less chlorine 
at low than at high temperatures? The answer to this is plain. The ascending 
part of the curve represents the solubility of a solid (chlorine hydrate) in water, 
and this solubility follows the general law. The descending portion represents 
VOL. XXX. PART III. 5 C 
