EESINS. 211 



the action of an enzyme, emulsin, splits up into benzaldehyde, 

 hydrocyanic acid, and glucose 



C 20 H 27 NO n + 2H 2 = C (5 H 5 CHO + HCN + 2C (i H 12 O fi . 

 Similarly, allyl-isothiocyanate is not present as such in 

 mustard seeds, but as a compound, potassium myronate, 

 KC 10 H 1H NS 2 10 . This, under the action of an enzyme, myrosin, 

 is split up as follows : 



KC 10 H 18 NS 2 10 - C 3 H 5 NCS + KHSO 4 + C H 12 O . 



The Resins are now regarded as the products of the oxida- 

 tion of terpenes rather than the mother substances from 

 which terpenes are derived. They have no uniformity of con- 

 stitution as is the case w r ith the fats, but present wide 

 differences in chemical character. They may be divided into 



1. The Balsams, which consist of resinous substances 

 associated with terpenes. Canada balsam, obtained from Pinus 

 balsama of South America, and crude turpentine or Venice 

 turpentine, from many pines, are good examples. 



Crude turpentine consists of ordinary rosin or colophony 

 dissolved in turpentine oil. Kosin consists mainly of sylvinic 

 acid, C 20 H 30 2 ,' :: a monobasic acid, whose sodium salt is used in 

 the manufacture of cheap soaps. 



2. The Solid or Hard Resins. These are amorphous sub- 

 stances of vitreous character, which contain very little terpene. 

 They consist chiefly of esters, alcohols, anhydrides, and acids of 

 the aromatic series, generally of very complex character. In 

 addition there are present certain substances which are neither 

 hydrocarbons, esters, alcohols, anhydrides, nor acids, and 

 which are called resenes. Many different bodies of this class 

 have been isolated and analysed, but their constitution is not 

 known, e.g., from copal a substance C 25 H 8rt 4 , from dragon's 

 blood C 20 H 40 O 4 . Many other substances of complicated 

 character have been obtained from the hard resins. 



To the class of hard resins belong many substances of great 

 importance in varnish making, &c., e.g., copal, dammar, elemi, 

 sandarach, amber, &c. 



* Fahrion, Zeit. ftir augen. Chemie 1901, Dec. 3rd. 



