30. Sublimation

30.    Sublimation. The process by which volatile solid substances are reduced to the state of vapor by heat, and again condensed in solid form. It differs from ordinary distillation only in being confined to dry solid substances, and in the heat employed being, in general, much greater. Calomel, corrosive sublimate, and sal ammoniac, are thus prepared.

31. Trituration

31.    Trituration. The reduction of a solid body to powder by nibbing. This is effected on a small scale by means of a pestle and mortar; and on a large scale by grinding in a mill, or with a muller or a slab made of porphyry or other hard substance; this latter is termed porphyrization.

32. Washing

32.    Washing. This is resorted to in chemistry for two widely different purposes. When a substance contains both soluble and insoluble matter, the soluble portion can be separated from the insoluble by washing; this is called Lixiviation. (See No. 23 (Lixiviation).)

"When it is desired to cleanse or remove impurities from an insoluble powder, this is also effected by washing. (See Nos. 14 (Elutriation) and 3841.)