MICROCHEMIS TR Y. 8 1 



not reduce Fehling's solution, and it is also doubtful 

 whether this substance occurs in recognizable quantity 

 within the plant (cf. Beilstein, I, 883). 



6. Sulphur Compounds. 



126. Of sulphur compounds of the fat group only oil of 

 garlic and oil of mustard have been studied with reference 

 to their microchemical recognition. 



a. Garlic Oil, Ally I Sulphide, (C 3 H 5 ) 2 S. 



Garlic oil, which occurs in almost all parts of the various 

 species of A Ilium, gives the following reactions: 



With platinum chloride, a characteristic yellow precipitate ', 



With mercury salts, a white precipitate ; 



With palladous nitrate, a kermes-brown precipitate ; 



With a \-2% solution of silver nitrate, a finely granular 

 precipitate of silver sulphide ; 



With concentrated sulphuric acid, a beautiful red color ; 



With gold chloride, a yellow precipitate. 



For microchemical purposes the palladous nitrate and 

 silver nitrate serve best, according to Voigt (I), and it is 

 convenient to place large portions of the plants in the 

 solution and to hasten its penetration by the aid of the air- 

 pump. After hardening in alcohol, sections may be cut. 



b. Mustard-oils, Alkylthiocarbimides, SC : N-R. 



127. The mustard-oils include a group of homologous 

 compounds which contain the atom group SC : N and an 

 alkyl radical. The best known of them is allylic mustard- 

 oil (allyl sulphocyanate, C 3 H 5 CNS), which is separated by 

 the ferment myrosin from potassium myronate, which be- 

 longs to the glucosides and occurs especially in the seeds of 

 black mustard. The reactions proposed by Solla (II) fof 

 the microchemical recognition of allyl mustard-oil have 

 proved useless on being tested by Bachmann (VI) and 

 Molisch (I, 33), so that we have at present no special re- 

 action for those bodies which is microchemically applicable. 



