230 
ON THE ESSENTIAL OIL OF MUSTARD. 
suffice to prove that the conversion takes place as I have 
just described it. 
But I desired to have chemical proofs. I therefore col- 
lected the oil which had been produced in the reaction; it 
was colourless, possessing in a high degree the character- 
istic odour of garlic, and presented the reactions described 
by M. Wertheim; shaken with a solution of nitrate of silver 
it afforded a black precipitate of sulphuret ; with the bi- 
chloride of mercury (when the aqueous solution was slightly 
heated to dissolve more oil) it yielded a white, and, with 
the bichloride of platinum, a yellow precipitate. 
Burnt with oxide of copper, it yielded the same relative 
quantities of carbon and hydrogen as were obtained by M. 
Wertheim in the analysis of the oil extracted directly from 
garlic, and rectified without potassium, viz. — 
Rectified oil of garlic. Oil of 
My produce. Wertheim. Mustard. 
Carbon 58.8 59.1 48.5 
Hydrogen 8.4 8.2 5.1 
I have not been able to make more analyses, from want 
of material. 
The salt which separates in this reaction is sulphocyanide 
of potassium; in fact it dissolves easily in water, and gives 
with the persalts of iron the characteristic dark red colour ; 
it also yields a white precipitate (protosulpho-cyanide ot 
copper,) with a mixture of deuto-sulphate of copper and of 
protosulphate of iron, &c. I was unable to discover sul- 
phuret or cyanide. 
However, in rectifying the artificial oil of garlic a second 
time over potassium, I found much sulphuret in the resdue, 
This reaction appears secondary. Besides, to understand 
the reaction well, it will be necessary again to examine the 
gas which is evolved, which want of material prevented 
me from doing. 
The above results seem to be sufficiently conclusive to 
