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Volume 52, 1920
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Art. XXVI.—The Influence of Salts of the Alkali and Alkaline-earth Metals on the Solubility in Water of Calcium Carbonate (a) in the Presence of Air free from Carbon Dioxide, (b) in the Presence of Excess of Carbon Dioxide.

[Abstract communicated by W. P. Evans, M.A., Ph.D., to the Philosophical Institute of Canterbury, 6th August, 1919; received by Editor, 31st December,. 1919; issued separately, 15th June, 1920.]

The series of experiments herein described was carried out in order to determine how the solubility in water of calcium carbonate was affected by the presence of small quantities of the salts of the alkali and alkaline-earth metals, the temperature and pressure being approximately constant.

The quantities added varied from 0.0005 to 0.1 mole per litre, while the temperature lay between 11° and 12° C.

Apparatus.

The apparatus employed in the first series of experiments consisted of a number of wash-bottles connected in series. The air was sucked through these at a constant head, the flow being adjusted by a micrometer-screw in parallel with a pressure-gauge.

The air was freed from carbon dioxide by means of soda-lime followed by a solution of caustic potassium hydroxide.

In the second series of experiments carbon dioxide was passed through the wash-bottles direct from a cylinder the needle-valve of which replaced the screw-tap of the previous apparatus.

Conclusions.
1.

The solubility of calcium carbonate in water increases regularly with the addition of increasing small amounts of (a) ammonium, sodium, potassium, and magnesium sulphates; (b) ammonium and sodium nitrates; (c) ammonium and magnesium chlorides.

2.

The solubility of calcium carbonate in water decreases regularly with the addition of increasing small amounts of (a) ammonium, sodium, and potassium carbonates; (b) potassium nitrate; (c) potassium chloride; (d) disodium hydrogen phosphate.

3.

The solubility in water of calcium carbonate exhibits irregularities in the presence of small quantities of sodium chloride.

4.

The solubility in water of calcium bicarbonate increases regularly with the addition of increasing small quantities of (a) ammonium, sodium, potassium, and magnesium sulphates; (b) ammonium, sodium, and potassium nitrates; (c) ammonium, sodium, potassium, and magnesium chlorides.

5.

The solubility in water of calcium bicarbonate decreases regularly with the addition of increasing small quantities of (a) ammonium, sodium, and potassium bicarbonates; (b) calcium chloride; (c) disodium hydrogen phosphate.

6.

As regards the alkalies, calcium carbonate appears to be most soluble in the ammonium salt of a given acid and in the sulphate of a given base.