320 
ON TIIE PURITT OF THE OTTO OF ROSES. 
the same color; whilst the oil of geranium becomes of an 
apple-green color, and retains it for some time. 
This test will serve to distinguish the two oils when in a 
state of purity, and may even serve to recognise oil of gera- 
nium containing the otto, because of the yellow color which 
it imparts to the latter ; but it is evident that it cannot serve 
to determine the presence of the oil of geranium in the otto 
of roses. 
Sulphuric Acid Test. — One or two drops of the oil to be 
tested is put into a watch-glass ; the same number of drops 
of very concentrated sulphuric acid are added, and the two 
fluids mixed with a glass rod. All the oils are rendered 
more or less brown by this proceeding; but — - 
The otto of roses retains the purity of its odor. 
The oil of geranium acquires a strong and disagreeable 
odor, which is perfectly characteristic. 
The odor of the oil of rose-wood is increased, and be- 
comes somewhat unctuous. It is not, however, charac- 
teristic. 
The commercial oil of rose-wood acquires an odor dis- 
tinctly like that of cubebs. 
Of these three methods, that with sulphuric acid is by far 
the best for distinguishing the otto of roses from the oil of 
geranium, and for the recognition of the second in the 
former, The iodine-test is also very certain, but. it requires 
considerably more time. The nitrous acid test will serve to 
recognise the two oils when not mixed, or even to detect 
the otto of roses in the oil of geranium ; but not the latter 
when mixed with the former. — lb., from Jour, de P/iarm. 
