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Chlorine is fairly soluble in water, 2.68 volumes of the gas dissolving in 1 volume of water at 15°. The volumes of chlorine, reduced to 0° C. and a total pressure (gas + water vapour) of 760 mm., dissolved by 1 volume of water are:
| 0° | 10° | 15° | 20° | 25° | 30° | 40° | 50° | 60° | | 4.61 | 3.095 | 2.635 | 2.260 | 1.985 | 1.769 | 1.41 | 1.20 | 1.0 |
Below 9.6° the saturated solutions are metastable, being supersaturated with respect to the solid chlorine hydrate, in presence of which the solubility has a maximum value, 2.98, at 9.6°. In the figures given, it is assumed that the total pressure (chlorine + water vapour) is 1 atm. The solution, which may be prepared by passing chlorine through water in Woulfe's bottles, is pale yellow in colour, smells strongly of the gas, and is called chlorine water. The solution possesses bleaching and oxidising properties. It precipitates sulphur from a solution of sulphuretted hydrogen: H2S + Cl2 = 2HCl + S; it liberates iodine from a solution of potassium iodide: 2KI + Cl2 = 2KCl + I2, but with an excess of chlorine water the iodine dissolves, forming iodine chloride, ICl. A solution of sulphur dioxide (sulphurous acid) is oxidised to sulphuric acid: 2H2O + Cl2 + SO2 = H2SO4 + 2HCl.
When a flask of chlorine water, inverted in a basin of the same liquid, is exposed to bright sunlight, it is decomposed with evolution of bubbles of oxygen, and a solution of hydrochloric acid is left: 2H2O + 2Cl2 = 4HCl + O2. In diffused daylight some chloric acid is also formed: 5Cl2 + 5H2O = HClO3 + 9HCl + O2.
Chlorine is less soluble in salt solution than in pure water, but it is more soluble in concentrated hydrochloric acid than in water, perhaps on account of the formation of a compound HCl3.
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