Origin. - The seed of Brassica nigra (L.) Koch.

Both the white and black mustard are annual plants, indigenous in Southern Europe and Western Asia, cultivated, and sometimes found wild in the United States.

Description and Properties. - White mustard seeds are almost globular, about 1/12 inch (2 Mm.) in diameter, with a circular hilum; testa yellowish, finely pitted, hard; embryo oily, with a curved radicle and two cotyledons, one folded over the other; free from starch; inodorous; taste pungent and acrid.

Black mustard seeds resemble the preceding in shape, but have a diameter only of 1/25 inch (1 Mm.); blackish-brown or deep reddish-brown, with a testa covered with shallow pits, and when crushed and macerated with water acquiring a strong and pungent odor.

White mustard seeds contain an almost tasteless, yellowish, fixed oil, and a glycoside known as sinalbin, which is the chief constituent. This substance may be converted into sulphocyanate of acrinyl (the volatile oil of mustard) by the action of the ferment myrosin and water:

Sinalbin. Volatile Oil.

C30H44N2S2O10 = C8H4(OH)CH4NCS + Cl6H13NOH1SO4 + C6H12O6.

Black mustard seeds contain the same fixed oil as the white mustard, and a glycoside, sinigrin, which by the action upon it of myrosin in contact with water converts it into allyI isosulphocyanate (a volatile oil):

Sinigrin. Volatile Oil.

C10HI8KNS2O10 =CSNO3H5 + C6H1206 + KHSO4

To this volatile oil of mustard, which is official, are due both the pungent taste and odor of the moistened powder.

DOSS. - 1-4 drams (4.0-15.0 Gm.) [120 grains (8.0 Gm.), U. S. P.].

Official Preparation (of Black Mustard Seed). Charta Sinapis - Chartas Sinapis - Mustard Paper.