CRUCIFER^ 497
or in the seeds, have been proposed. The following are amongst those of
the greatest accuracy. Dieterich has proposed the following method :—
Three grams of the oil and 3 grams of alcohol are shaken in a flask
with 6 grams of a 10 per cent, solution of ammonia. It should become
clear after standing for a few hours, or rapidly if warmed to 50° C., and
deposit crystals of allyl thio-urea (thiosinamine)
po/NH. C 3 H 5
\NH 2
To determine the quantity, decant the mother liquor and evaporate it
slowly on the water-bath in a tared capsule, adding fresh portions slowly
as the smell of ammonia disappears. Then add the crystals from the flask
to those in the capsule, rinsing the flask with a little alcohol, and heat
the capsule on the water-bath to a constant weight. Three grams of
oil should yield between 3 * 25 and 3*5 grams of thiosinamine, which
should melt at 70° to 74°. One hundred and sixteen parts of thiosina-
mine correspond to 99 parts of allyl iso-thiocyanite.
Gadamer
l
recommends the following process. The mustard oil is
dissolved in alcohol to form an exactly 2 per cent, solution. Five c.c
(4*2 grams) of this solution are allowed to remain with 25 c.c. of deci-
normal solution of silver nitrate and 5 c.c. of ammonia for twenty-four
hours in a well-stoppered 50 c.c. flask. It is then made up to 50 c.c. with,
water and filtered from the precipitated silver sulphide; 25 c.c. of the
filtrate are mixed with 4 c.c. of nitric acid and a few drops of ferric sulph-
ate solution, and titrated with deci-normal ammonium thiocyanate solu-
tion, until the characteristic red colour of the ferric thiocyanate appears.
From 4*1 to 4*5 c.c. of the solution (corresponding to 1*85 to 2*0 per
cent, of allyl thiocyanate in the alcoholic solution) should be required.
Griitzner
2
converts the thiocyanate into thiosinamine, which he oxi-
dises with peroxide of sodium, and weighs the resultant sulphuric acid as
barium-sulphate. From the figures obtained in his analysis, Griitzner
concludes that a mustard oil containing 28*60 per cent, of sulphur
(equivalent to 88*48 per cent, of iso-thiocyanate) may be regarded as pure.
P. Eoeser
3
proposes to modify Gadamer's method for the determination
of the sulphur content of oil of mustard so as to determine the excess of
silver nitrate, in an ammoniacal solution, instead of an acid solution
according to Volhard's method, as is usually done. According to this,
the process should be as follows: When the conversion of the thiosin-
amine with silver nitrate, after twenty-four hours' standing, has taken
place, an excess of one-tenth normal solution of potassium cyanide is
added to 50 c.c. of the clear filtrate, and the excess of potassium cyanide
titrated back with one-tenth normal solution of silver nitrate, in the
presence of a few drops of a weak ammoniacal solution (5 per cent.) of
potassium iodide.
Schimmel & Co. recommend the following method : About 5 grams
of a solution of 1 gram mustard oil in 49 grams alcohol are mixed in a
measuring flask of 100 c.c. capacity with 50 c.c. deci-normal solution of
silver nitrate and 10 c.c. of solution of ammonia (dl5o 0
*
960); the flask is
then closed, and with frequent agitation left standing for twenty-four
hours with the light excluded. The flask is then placed for half an hour
in water at 80°, during which time it is again repeatedly shaken, then
1
Arch. Pharm. (1899), HO, 237.
2
3 Ibid., 195.
Jour. Pharm. Chim., vi. 15 (1902), 361.
VOL. i. 32