BATH, in Chemistry

BATH, in Chemistry. Several kinds of apparatus employed to transmit heat are called baths; but the substances most frequently used by chemists for this purpose are water and sand. When water is employed, it is called Balneum Maria, or water bath; which is very much used, very convenient for many operations, and may be employed successfully for all degrees of heat inferior to that of boiling water. As water, when exposed to fire in any vessel from which it can evaporate, does only receive a determinate degree of heat, which always remains the same when once it has arrived to the boiling heat, it follows, that by the water bath, a degree of heat always equal may be transmitted with

certainty. Farther, this degree of heat being incapable of burning, or of communicating an empyreumatic quality to matters susceptible of it, the water bath has also the advantage of not exposing substances to this inconvenience. When vessels in which distillations and digestions are made, are placed in sand, then a sand bath is formed. This intermediate substance of sand is very convenient, to moderate the too great activity of the naked fire, and to transmit any degree of heat, from the weakest to a red heat. As this bath is attended with less trouble, and requires less apparatus than the water bath, it is much used in laboratories. Nothing is requisite for the sand bath, but an earthen or iron vessel filled with fine sand, which is fitted into a furnace, and capable of containing the cucurbits, retorts, matrasses, or other vessels containing the matter to be operated upon.