128 Journal of Agricultural Research vol. xx, no. a 



From these data it may be seen that the oil consists largely of crotonyl 

 isothiocyanate, which, since it is the chief constituent of volatile oil of 

 rape, corroborates the botanical findings that the seed is related to the 

 rapes and not to the mustards. It was noted that the crotonyl isothio- 

 cyanate did not have the odor of volatile mustard oil (allyl isothiocya- 

 nate) but had an odor suggestive of turnip or cabbage. Furthermore, 

 it did not have the typical irritating effect of mustard oil on the mucous 

 membrane of the nose and on the eyes nor a blistering effect on the skin. 



DETERMINATION OE VOLATILE OIL IN MUSTARD SEED AND MUSTARD 



SUBSTITUTES 

 In the course of this work it became necessary to determine the amount 

 of volatile oil yielded by different varieties of mustards and mustard 

 substitutes. Reference to the literature showed that there had been 

 marked variation in the methods followed by different analysts in the 

 determination of volatile mustard oils, especially in regard to the time 

 of maceration and the conditions for distillation. Wehrmann, Wegener, 

 Braunwarth, and Meyer (57) made an extended study of a number of 

 these methods in order to arrive at a quick, convenient method for the 

 determination of the volatile oil. In general, the studies here reported 

 have corroborated their findings, except with respect to the effect of 

 alcohol added before maceration (51 , p. 325). Carles (7, 8) has also con- 

 tributed valuable data to the solution of this problem. As a result of 

 these studies, the following method, based largely upon that of Gadamer 

 (13, 14), is recommended. 



METHOD 



Place 5 gm. of the ground seed (No. 20 powder) in a 200-mil flask, add 100 mils of 

 water, stopper tightly, and macerate for 2 hours at about 37 C. Then add 20 mils 

 of U. S. P. alcohol (95 per cent), and distill about 70 mils into a 100-mil volumetric 

 flask containing 10 mils of 10 per cent ammonium-hydroxid solution and 20 mils of 

 Njio silver nitrate solution. Mix thoroughly, stopper, and set the distillate aside 

 overnight, heat to boiling on a water bath (in order to agglomerate the precipitate), 

 cool, make up to 100 mils with water, and filter, rejecting the first portions. Acidify 

 50 mils of the filtrate with about 5 mils of concentrated nitric acid and titrate with 

 Njio ammonium thiocyanate, using 2 mils of 10 per cent ferric-ammonium-sulphate 

 solution for an indicator. Each mil of Njio silver nitrate consumed is equivalent to 

 0.004956 gm. of allyl isothiocyanate or 0.005657 gm. of crotonyl isothiocyanate. 



The method is based on the hydrolysis of the glucoside by an enzym, 

 both present in the seed. A volatile oil, glucose, and potassium hydrogen 

 sulphate are formed. 



^^OSO,OK ^OYL 



C— S — "- C 6 H u 5 + H 2 = C SH + KHS0 4 + C 6 H 12 6 



\NCH 5 \NCJL 



Sinigrin 



>^OH 



C SH > CSN - C 3 H 5 +H 2 



\NC 3 H 5 • 



Allyl isothiocyanate 



