_Heat liberated._ | _Heat absorbed._ | Formation of Ca(OH)_2 16O.1 | Formation of acetylene 58.1 | Decomposition of water 69.0 | Decomposition of carbide 3.9 | Balance 29.1 _____ | _____ | Total 160.1 | Total 160.1 Therefore when 64 grammes of calcium carbide are decomposed by water, or when 18 grammes of water are decomposed by calcium carbide (the by- product in each case being calcium hydroxide or slaked lime, for the formation of which a further 18 grammes of water must be present in the second instance), 29.1 large calories are set free. It is not possible yet to determine thermo-chemical data with extreme accuracy, especially on such a material as calcium carbide, which is hardly to be procured in a state of chemical purity; and so the value 28.454 calories experimentally found by Lewes agrees very satisfactorily, considering all things, with the calculated value 29.1 calories. It is to be noticed, however, that the above calculated value has been deduced on the assumption that the calcium hydroxide is obtained as a dry powder; but as slaked lime is somewhat soluble in water, and as it evolves 3 calories in so dissolving, if sufficient water is present to take up the calcium hydroxide entirely into the liquid form (_i.e._, that of a solution), the amount of heat set free will be greater by those 3 calories, _i.e._, 32.1 large calories altogether.