Sinapis Alba

White mustard. The seed of Brassica alba Linné (Nat. Ord. Cruciferae).

Sinapis Nigra

Black mustard. The seed of Brassica nigra.

Charta Sinapis

Mustard-paper.

Composition

When water is added to pulverized black mustard, pungent, irritating fumes are given off. These fumes consist of the volatile oil of mustard (allyl sulphocyanide). This volatile oil is produced by a reaction between certain constituents of the seeds—sini-grin (myronate of potassium) and myrosin—in presence of water, and at a temperature below 100° Fahr. The boiling-temperature destroys the ferment, myrosin, and hence prevents the formation of the volatile oil. Mustard contains also a bland fixed oil, which may be procured by expression.

White mustard contains an indifferent, crystalline substance, sinal-bin, and myrosin. Sulphocyanate of acrinyl, a product of the reaction between sinalbin and myrosin, is the rubefacient principle of white mustard (Flückiger and Hanbury). White mustard contains also an alkaloid—sinapine. The chemical composition of the two kinds of mustard is, it will be seen, closely analogous. Myrosin exists in white mustard in larger proportion than in black, hence a considerably larger quantity of the volatile oil of mustard is formed when an addition of white mustard is made to the black.

A great variety of plasters and liniments (some referred to already in their appropriate connections) are employed to induce a rubefacient action.