Note 639 — PHARMACOLOGIA. (continued 7)

Our English Salt is generally thus contaminated; for which reason it is unfit for the curing of several kinds of fish; this will not appear strange, says Mr. Parkes, when it is considered that merely its own weight of water is all that is necessary for the complete solution of muriate of magnesia; a circumstance which renders it impossible to preserve such salt for any length of time in a dry state. This muriate however might be separated from common salt, on a large scale, for one shilling per cwt. By exposing the salt to a gentle heat in reverberatory furnaces, the muriatic acid of the magnesian muriate will fly off, and the magnesia (on a subsequent solution of the salt) will be precipitated. It is well known that muriate of magnesia begins to part with its acid at a temperature a little higher than that of boiling water.