CRUCIFEBJE 499
Brioux
1
describes a method of estimating allyl and crotonyl iso-sul-
phocyanate in oil-cakes and mustard-flours. He places 25 grams of the
finely crushed oil-cake in a flask of one litre capacity, adds 500 c.c. of
distilled water, 2 grams of sodium fluoride dissolved in a little water,
then heats in the water-bath at 37° to 40° C. after having closed the flask
with a cork. If the oil-cakes or flours are derived from foreign varieties,
it is advisable to prolong the duration of heating to three or four hours.
To the same flask are then added 20 to 25 c.c. of 95 per cent, alcohol,
and the liquid is distilled on the sand-bath ; 150 c.c. of the distillate are
•collected in a 250 c.c. marked flask, previously containing 10 c.c. of pure
ammonia; then 25 to 50 c.c. of deci-normal silver nitrate solution are
Added and the flask is heated for an hour under a reflux condenser in a
water-bath maintained at about 85° C. After cooling, the volume is made
up to 250 c.c. the liquid is shaken and filtered, and finally 125 c.c. are
taken for the estimation of the excess of silver by means of deci-normal
ammonium sulpho-cyanate. Before making this latter titration care must
be taken to add 10 c.c. of pure nitric acid and 10 c.c. of a 10 per cent,
solution of iron alum. From the quantity of silver necessary for the
formation of the precipitate of silver sulphide, the percentage of crotonyl
or allyl mustard oil is readily calculated.
Huber and Van der Wielen
2
determine the volatile oil (thiocyanate)
in mustard seeds as follows. Their experiments were directed towards
determining to what extent the time of maceration of the crushed seeds
in water influences the result. Five gram samples of the mustard were
macerated for 1, 2, 4, 18, and 20 hours respectively, with 100 c.c. of
water, after which were added 20 c.c. of alcohol and 2 c.c. of olive oil.
Of the mixture about 50 c.c. were distilled into a 100 c.c. measure con-
taining 10 c.c. of ammonia, taking care that the delivery tube was im-
mersed in the ammonia. After adding 20 c.c. of deci-normal silver
nitrate solution the whole was heated over a water-bath until the silver
sulphide had aggregated and the liquid was clear. The liquid was then
•cooled and made up with water to 100 c.c., the excess of silver nitrate
was determined by titration with deci-normal ammonium thiocyanate,
using iron alum as an indicator.
The following results were obtained :—
After 1 hour of maceration 0'9 per cent, and 09 per cent.
„ 2 hours „ 1-15 „ „ 1-15
4 „ „ 1'03 „ „ 103
„ 18 „ „ 0-7 „ „ 0-7
„ 24 „ „ 0-77 „ „ 0-77
From the above table the ideal period of maceration is two hours.
Having once added the alcohol to arrest fermentation, the time the liquid
is allowed to stand before distillation seems to have no influence upon
the results; after the two hours' maceration and addition of alcohol, it
was allowed to stand overnight.
White mustard seeds, from Brassica alba, contain the glucoside
sinalbin, C 30 H 42 N 2 S 2 O 15 , which on decomposition in the same manner as
the glucoside of black mustard yields glucose, sinapine sulphate, and
the evil-smelling oil, acrimyl-thiocarbimide (p-hydroxy-benzyl-iso-thiocy-
.anate). The reaction takes place as follows:—
C3UH 42 N 2 S 2016 + H 2 0 = C 6 H 1206 + C 16 HMN0 6. H 2 S0 4 + C 7 H 7 O.NCS.
1
Ann. Chim. Anal. Appliquie, 17, 3.
*
Pharm. Weeicblad (1915), 39.