408 
PHARMACEUTICAL MEETING. 
follows :—The essential oil is mixed in a flask with about three times its bulk of 
ordinary hydrochloric acid diluted with a small quantity of water, a condenser 
attached, and distillation started. As soon as the oil begins to come over pretty 
freely, a quantity of water is added and distillation proceeded with. The oil is 
afterwards separated from the aqueous portion of the distillate ; it is slightly 
acid, and to remove this a little piece of quicklime is put into it, which at the 
same time helps to dry the oil. If hydrate of lime be used for this purpose, 
the essence becomes slightly discoloured. 
Supposing the change represented in the equation above to take place strictly 
as there shown, a proportion of hydrocyanic acid in the oil amounting to 8 per 
cent would cause a loss of no less than 31'4 per cent, of the hydride, in the 
form of the acid described ; 5 per cent, of hydrocyanic acid would remove 19'6 
per cent, of hydride. Such a deficiency would be, of course, out of the question ; 
but I have made in the manner described two rough quantitative experiments, 
and believe that the loss on the large scale would not amount to more than 
from 15 to 17 per cent., which would include hydrocyanic acid, benzoic acid, 
benzoine, and all the other impurities of the essence. 
I now wish to describe another method, which was suggested at a meeting of 
the Chemical Discussion Association by my friend Mr. Broughton, and which 
had also occurred to myself, but at that time I had no opportunity of making 
the experiment. 
Chemists have found that all the aldehycls with which we are acquainted form 
definite crystalline compounds with the alkaline bisulphites; hydride of benzoyl, 
possessing as it does the characters of an aldehyd, being, in fact, the aldehyd 
of the benzoyl series, is no exception to this rule. 
If therefore the crude essence of almonds be shaken up with three or four 
times its volume of a tolerably strong solution of bisulphite of soda and then 
allowed to rest, the mixture becomes warm and the hydride of benzoyl is all con¬ 
verted into a crystalline mass, having the composition represented by the fol ¬ 
lowing formula,—C 14 II 5 Na0 2 , S 2 0 4 ,o Aq. These crystals removed from the 
mother-liquor, which should be preserved, drained, and^dried at a very gentle 
heat and then dissolved in water, carbonate of soda in excess added, and the 
mixture distilled, yield hydride of benzoyl in a condition of absolute purity. 
By this plan, theoretically speaking, there is no loss beyond the actual impuri¬ 
ties of the crude substance. This is certainly a recommendation, but a little 
trouble is involved in the double operation of preparing the crystals and their 
subsequent decomposition. 
Having obtained the purified essence of almonds by any process that is most 
efficient, another desideratum is felt in the difficulty of preserving it from under¬ 
going that oxidation and change with which every one is familiar. By exposure 
to the air, as every one knows, absorption of oxygen occurs and the liquid hy¬ 
dride is converted into crystalline benzoic acid,— 
Ci 4 II 6 0 2 + 0 2 ^ C 14 H 6 0 4 , 
and this change proceeds much more rapidly with the purified than with the 
unpurified oil. 
For this defect there is a simple remedy, which I think is as efficient as any¬ 
thing of the kind can ever be expected to be. It is well known that in the pre¬ 
sence of moisture oxidation is effected with infinitely greater facility than other¬ 
wise. Numerous examples of this may be easily adduced, but I can remember 
none more striking than the formation of rust upon the surface of iron. If, 
then, the purified essence of almonds be perfectly dried by a lump of chloride of 
calcium introduced into it, the oxidation is retarded in a very marked degree. 
I cannot say that the^essence attains the degree of permanence enjoyed by the 
crude substance, but certainly the improvement is of the most decided character. 
