NOTE ON PURIFIED ESSENTIAL OIL OF ALMONDS. 
325 
liquid; the point on the stem of the hydrometer, cut by the under surface of 
the liquid, will be the specific gravity. A copy of these directions will be found 
in the case, as sold by Mr. Casella. 
This particular hydrometer might be termed a Petroleometer; that name 
w'ould, however, perhaps best designate the whole box or set of articles. The 
most accurate method of taking specific gravities is of course the specific-gravity 
bottle ; but a hydrometer, if well made, gives, I find, numbers varying not more 
than one degree from those of the bottle, while its use involves far less trouble 
and expense. 
As an indication of the extent to which confidence can be placed in an i£cniting- 
point of petroleum, taken in the manner recommended, I may state that two 
different observers, experimenting at different times on three different specimens 
of petroleum placed before them without distinguishing marks, gave igniting- 
points in which the greatest limit of variation was one degree. It would doubt¬ 
less be easy for an analyst, by processes of fractional distillation, to obtain even 
from safe petroleum, vapour that would be inflammable at 60° Fahr,, or even 
at freezing temperatures; but it w'ould be absurd to regard such petroleum as 
dangerous, or to use such a fact as evidence of the weakness of any method of 
determining the igniting-point of refined petroleum. What I claim for the 
method above described is, that it accurately shows the temperature at which 
petroleum, as used by the public, is dangerous. It surely is not too much to 
expect that the method will be adopted by the trade, and that no mineral oil 
will be supplied to the public unless guaranteed to give off no inflammable va¬ 
pour below 100 degrees of Fahrenheit’s thermometer. Only by some such 
means will explosions in lamps, etc., be avoided, explosions which are always 
alarming, frequently the cause of loss of property by fire, and occasionally re¬ 
sulting even in loss of life. 
17, Bloomsbury Square, London. 
NOTE ON PURIFIED ESSENTIAL OIL OF ALMONDS. 
BY WILLIAM A. TILDEN, F.C.S., 
DEMONSTRATOR IN THE LABORATORY OF THE PHARMACEUTICAL SOCIETY OF GREAT 
BRITAIN. 
A few days ago, I came upon two specimens of essential oil of almonds which 
I had prepared in 1864 in illustration of a short communication I had the honour 
of reading at one of the evening meetings of this Society. I suggested, at that 
time, that it was probable this essential oil might be rendered more permanent 
than in the purified state it is generally found to be by introducing into it some 
fused chloride of calcium, so as to remove from it the last traces of moisture. 
These specimens I produce in support of that suggestion ; they have been 
prepared upw'ards of two years, and have been preserved side by side under 
precisely the same conditions. The one, as you see, is filled with crystals of 
benzoic acid ; the other, in which is placed a fragment of chloride of calcium, 
is perfectly free from crystalline deposit, and remains quite fluid. These bottles 
seem to me to exhibit clearly the very decided influence of perfect drying.* 
Shortly after the publication of my paper, a wholesale drug firm in this city 
wrote "to the ‘Pharmaceutical Journal,’ announcing that the purified essence 
I am informed by Mr. C. Umney, who is in the habit of purifying essential oil of 
almonds on a large scale, that he has found the above plan of desiccation by means of 
chloride of calcium to succeed perfectly in preventing change in the purified oil. 
