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 base, have been forced to denominate the unknown base from the name of the known acid, as happens in the case of the acid which is procured from sea salt.

To disengage this acid from the alkaline base with which it is combined, we have only to pour sulphuric acid upon sea-salt, immediately a brisk effervescence takes place, white vapours arise, of a very penetrating odour, and, by gently heating the mixture, all the acid is driven off. As, in the common temperature and pressure of our atmosphere, this acid is naturally in the state of gas, we must use particular precautions for retaining it in proper vessels. For small experiments, the most simple and most commodious apparatus consists of a small retort G, (Pl. V. Fig. 5.), into which the sea-salt is introduced, well dried, we then pour on some concentrated sulphuric acid, and immediately introduce the beak of the retort under little jars or bell-glasses A, (same Plate and Fig.). previously filled with quicksilver. In proportion as the acid gas is disengaged, it passes into the jar, and get to the top of the quicksilver, which it displaces. When the disengagement