(From esse, to be). Essential. It is an epithet for salts procured from vegetable juices, by crystallization. For the process, see Ace-tosa. When the viscous juices of vegetables are used in this process, the salt cannot be obtained without a previous fermentation to dissolve their tenacity Juices that contain an oil or a balsam will not easily yield their salt, for oils and balsams prevent its crystallization. These salts are not alkaline; but become such by burning.

The oils peculiar to different vegetables are also called essential; and are generally the volatile, containing the peculiar smell and taste of the plant.

Some fevers are called essential or idiopathic, to distinguish them from the symptomatic.

Essentialis sal. Essential salt. This name is given to all concrete saline substances, which preserve the principal qualities of the vegetable and animal bodies from which they were obtained. The usual method of preparing is by evaporating, to nearly the consistency of a syrup, the liquors containing them. The crystals which shoot from these liquors may be depurated by dissolving them in water, filtrating, evaporating, and crystallizing.

Very often the salts thus obtained from animal and vegetable matters are only vitriolated tartar, vitriolated natron, nitre, common salt, and similar neutral salts, which only merit the name of essential salts when intimately combined with the peculiar oil of the plant.