lead, will remove empyreuma, if present. The first of these substances is the most effective; the power of the others being in the order in which they are printed. In distilling the weaker acids and vinegars, it is found useful to add from 25 to 30% of chloride of sodium, which, by raising the boiling-point of the liquid, allows the acid the more freely to pass over (Stein); but this addition proves disadvantageous when any sulphuric acid is present, in which case sulphate of soda may be employed instead. If this addition be not made, the whole of the acid cannot be obtained without distillation to dryness, and the generation of empyreuma. On the small scale, glass retorts are usually directed to be used, but glass alembics or flasks are more convenient and safe, as already noticed. In the preparation of the pure acid, care should be taken that the acetate of soda does not contain common salt, as the carbonate of soda prepared by calcination, and frequently used to form the acetate, is generally contaminated with it, and yields up its hydrochloric acid or chlorine during the process of distillation, thus vitiating the product. In all the methods given the product becomes more concentrated in proportion to the dryness of the acetate and the strength of the oil of vitriol or muriatic acid employed. By using the one dry, and the other concentrated, glacial acid may always be obtained by collecting separately the last two fifths that come over, and submitting this to refrigeration. According to Melsens, pure GLACIAL ACETIC ACID is most advantageously obtained by distilling pure and dry acetate of potash with an excess of strong and moderately pure acetic acid, rejecting that which first passes over. Acetate of soda may be safely dried at a temperature of 400° to 450°, provided care be taken to avoid ignition from contact with sparks. A less heat is, however, quite sufficient to drive off the whole of its water of crystallisation. It is known to be dry by its assuming the appearance of a smooth oily liquid whilst hot. If, whilst heated, it emits fumes, it is suffering decomposition. The same applies to the other commercial acetates. Crystallised acetate of soda loses about 2/5ths of its weight by thorough drying.