22 BRASSICA SIXAPIS XIGRA 



and R+J. mustard seeds, are very small, and roundish in form. 

 rnally they have a deep reddish-brown colour, or sometimes 

 greyish, the surface being reticulated with minute pits ; internally 

 they are yellow. Their powder has a greenish-yellow colour. In 

 the entire state they are inodorous, and even when powdered dry ; 

 but when the seeds are triturated with water they exhale a 

 strong pungent odour so as to affect the eyes, and in some cases 

 even to cause a flow of tears. When masticated their taste is 

 at first bitterish, which is immediately followed by pungency. 



Black mustard seeds yield by expression an inodorous, non- 

 drying fixed oil, with a mild oily taste. The amount of oil thus 

 obtainable by pressure averages 25 per cent. The seeds also con- 

 tain a crystalline substance, commonly known under the name of 

 myronate of potash, but better characterised as sinigrin ; and an 

 albuminous body closely resembling the emulsin of almonds, and 

 termed myrosin. Siuigrin, as shown by Will and Korner, is a 

 compound of SulpHocyanide of Allyl, Bisulphate of Potassium, and 

 Sugar. There is no starch in the ripe seeds. The pungent principle 

 upon which the properties of black mustard seeds essentially depend 

 does not pre-exist in the seeds, but is obtained in the form of a 

 volatile oil when the macerated seeds are distilled with water (see 

 Oleum Sinapis). The fact that the pungent volatile oil does not 

 pre-exist in the seeds explains their want of odour in a dried 

 state. 



2 . OLEUM SIKAPIS. The volatile or essential oil of mustard, which 

 ^icial under the name of oil of mustard, does not pre-exist in 

 black mustard seeds, as just stated, but is produced whenever water 

 is added to the powdered seeds by the action of myrosin on the sini- 

 grin, just as the volatile oil of almonds (see Oleum Amygdala Amara) 

 is formed under the same circumstances by the action of emulsin on 

 amygdalin. The temperature of the water used should not exceed 

 122" Fahr., as a much higher degree of heat prevents altogether the 

 formation of the oil. It is to this oil that the pungent smell and 

 taste of black mustard, as well as its inflammatory action on the 

 skin, is due. Oil of mustard is colourless or pale yellow, of an 

 exceedingly pungent odour, and a most acrid and pungent taste. 



