78 PRACTICAL ORGANIC CHEMISTRY Potassium Ethyl Sulphate. KC 2 H 5 SO 4 . Pure ethyl hydrogen sulphate is difficult to prepare, as it is an oily liquid, very soluble in water, and easily hydrolysed. It is therefore usually isolated as the potassium salt, since potassium ethyl sulphate crystallises well from water, and is not readily hydrolysed in neutral or weakly alkaline solution. To prepare the potassium salt, the mixture of ethanol and sulphuric acid is boiled under reflux, cooled, and treated with an excess of calcium carbonate. 2C 2 H 6 HSO 4 + CaCO, = Ca(C 2 H 6 SO 4 ), + CO 2 + H 2 O The ethyl hydrogen sulphate is thus converted into the soluble calcium ethyl sulphate, whilst the excess of sulphuric acid is removed as insoluble calcium sulphate. The aqueous filtrate is then mixed with just sufficient potassium carbonate to give potassium ethyl sulphate, the insoluble calcium carbonate being now filtered off. Ca(C
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