potassa (po-tas's ah). 1

See potash. 2. Of the U. S. Ph., 1890, caustic potash (pota ium hydroxid). It corresponds to the p. caustic a of the Br. Ph. liquor pota ae. See liquor pota i i hydroxidis, under pota ium. [U. S. Ph., 1890, Br. Ph.]. p. caustic a. Caustic potash [Br. Ph.]. p. cum calce. P. with lime, Vienna caustic, Vienna paste; made by rubbing together equal parts of caustic p. and quick lime; a grayish white, deliquescent alkaline powder [U. S. Ph., 1890. p. cumoreta. See p. caustic a. p. fusa. A caustic prepared by evaporating liquor pota ae till water ceases to escape, drying the residue on a warm stone, and break- G78 ing into pieces when cold. p. sulphur at a. 1. Liver of sulphur, consisting e entially of two equivalents (about 65 per cent.) of pota ium tri sulphid and one equivalent (about 35 per cent) of pota ium thiosulphate. Pure p. sulphur at a (liver of sulphur) is an amorphous substance, liver colored when fresh, afterward of. a greenish or yellowish hue, turning to a dirty green if the acce of air is not prevented. It has an odor of hydrogen sulphid, is deliquescent in moist air, and is completely soluble in 2 parts of water. 2. A preparation made like that of the 1 st def., but with crude pota ium carbonate and unwashed sulphur. It consists e entially of the same constituentc If, however, the proce of heating is car. ried too far, the thiosulphate is decomposed into pota ium sulphate and pota ium pent a sulphid, the latter breaking up again into sulphur and pota ium tri sulphid. This impure liver of sulphur has e entially the same properties as the purer variety, but is employed externally [U. S. Ph., 1890, Br. Ph.]. [Lat].