BENZENE SERIES. AROMATIC COMPOUNDS. 557 



substance also contained in mustard seed and acting as a ferment upon myronic 

 acid or its salts, potassium myronate is converted into dextrose, allyl mustard 

 oil, and potassium bisulphate. 



KC 10 H 18 NS 2 10 == C 6 H 12 6 + C 3 H 5 NCS -f KHSO 4 . 



Potassium Dextrose. Allyl mustard Potassium 



myronate. oil. bisulphate. 



Allyl mustard oil, C 3 H 5 NCS. Mustard oils are esters of isosulphocyanic 

 acid, HNCS. Ordinary mustard oil, obtained from sinigrin, as stated above, 

 contains the radical allyl, derived from the unsaturated hydrocarbon propylene, 

 C 3 H 6 . The univalent radical allyl is isomeric, but not identical, with the tri- 

 valent radical glyceryl, C 3 H 5 , derived from propane, C 3 H 8 . The difference may 

 be seen from the structural formulas : 



CH 2 CH=CH 2 , allyl. CH 2 CH-CH 2 , glyceryl. 



The triatomic alcohol glycerin, C 3 H 5 (OH) 3 , may be converted into the 

 monatomic allyl alcohol, C 3 H 5 OH, by various processes. From allyl alcohol 

 an artificial allyl mustard oil is manufactured. 



Mustard oil is a colorless or pale yellow liquid, which has a very pungent 

 and acrid odor and taste. When brought together with ammonia, direct combi- 

 nation takes place and crystals of thiosinamine (allyl-thio-urea), CS.N 2 H 3 .C 3 H 5 , 

 are formed . 



C 3 H 5 NCS + NH 3 = CS.N 2 H 3 .C 3 H 5 . 



Allyl sulphide, (C 3 H 5 ) 2 S, is the chief constituent of the oil of garlic. 



50. BENZENE SERIES. AROMATIC COMPOUNDS. 

 General remarks. It has been stated before that most organic com- 

 pounds may be looked upon as derivatives of either methane, CH 4 , 

 or benzene, C 6 H 6 , these derivatives being often spoken of as fatty and 

 aromatic compounds respectively. The term aromatic compounds 

 was given to these substances on account of the peculiar and fragrant 

 odor possessed by many, though not by all of them. Benzene and 



QUESTIONS. What are the three chief forms in which nitrogen enters into 

 organic compounds? What are amines and amides; in what respects do they 

 resemble ammonia compounds ? What is cyanogen, what is dicyanogen, and 

 how is the latter obtained ? How does cyanogen occur in nature, and which 

 non-metallic elements does it resemble in the constitution of various com- 

 pounds ? Mention some reactions by which hydrocyanic acid is formed, and 

 state the two processes by which the official diluted acid is obtained. What 

 strength and what properties has this acid ? State the composition of pure 

 potassium cyanide and of the commercial article. How is the latter made ? 

 Give reactions for hydrocyanic acid and cyanides. Explain the constitution 

 and give the composition of ferro- and ferricyanides. Give composition, mode 

 of manufacture, and tests of potassium ferrocyanide. What is red prussiate 

 of potash, how is it obtained, and by what reactions can it be distinguished 

 from the yellow prussiate ? 



