ON THE ESSENTIAL OIL OP MUSTARD. 229 
according to this chemist contains C 6 H 5 S. It is therefore 
a sulphuretted body like the essential oil of black mustard, 
but free from nitrogen. 
From the analyses of M. Loewig,and from the researches 
recently made by Dr. Will, we know that the essential oil 
of black mustard does not contain oxgen, andt hat its true 
formula is C 8 H 5 NS 2 . The result of M. Simon's observa- 
tions also appears to be, that the essential oil of the Scurvy 
grass {Cochlearia) is identical with that of mustard; more- 
over, M. Hubatka has proved that the horseradish yields 
the same essential oil; and M. Wertheim has also met with 
it in the oil obtained by distilling the root of another cruci- 
form plant, miliaria officinalis, with water. 
Considering these facts, and comparing the composition 
of the essential oil of garlic with that of mustard, I have 
been induced to try to convert one into the other by the 
means which science affords. 
The oil of garlic only differs from that of mustard by the 
elements of cyanogen and of sulphur ; we have, in fact, 
C 8 H* NS 2 = O H 5 S -f C 2 N + S. 
In acting with potassium on the oil of mustard, I had to 
take away the cyanogen as well as a part of the sulphur, 
and to set free the oil of garlic. 
My suspicions were entirely realized; when some pieces 
of potassium, previously dried over some chloride of calcium 
and rectified afresh, are thrown into the oil of mustard, it is 
attacked immediately. It may be slightly heated in a retort 
to favour the reaction; care must be taken, however, not to 
raise the temperature too much, for the substance might 
take fire, as has frequently happened to me. 
If the operation is performed with care, the substance 
does not become much coloured, some gas is disengaged, a 
white salt is deposited in the oil, and oil of garlic distils 
ovei. It is an interesting experiment, the difference of 
smell between the two oils being so striking: the smell of 
the garlic is immediately so evident, that this alone might 
