MISCEL ALNY. 
351 
alents of oxygen, and is converted into benzoic acid ; but half the oxygen 
absorbed combines with the hydrogen of the oil and forms water, which 
remains in union with the anhydrous benzoic acid."* 
Neither this oil nor the hydrocyanic acid pre-exist in the almond, but 
are developed by the action of the water, during distillation. 
Mr. Bell then made the following allusion to hydrocyanic acid in the 
state in which it is usually employed in medicine. 
The powerful effects of hydrocyanic acid, and the danger which is like- 
ly to result from inaccuracy in the dose, render uniformity in its strength 
of the highest importance, whilst its volatility and liability to decomposi- 
tion occasion considerable difficulty in attaining this object. 
Every time the stopper is removed from a bottle containing it, a portion 
of the real acid escapes, and althoughj,he quantity which is liberated at 
each time may be unappreciable, it is clear that when a bottle, containing 
an ounce or two, is nearly emptied in the usual routine of dispensing, the 
remaining portion must be considerably reduced in strength. This may 
serve to explain a circumstance which has occasionally excited the sur- 
prise of medical men, that after having daily increased the dose, with 
careful attention to the effects up to a certain point, a very slight acces- 
sion, or even a repetition of the last dose, has been known to produce 
violent and alarming symptoms. It has, in several instances, been dis- 
covered on investigation, that the last mixture was prepared from a fresh 
bottle of acid, which had not lost strength by exposure, while the former 
acid, by becoming gradually weaker, had misled the practitioner in esti- 
mating its effects. The extreme difficulty of guarding against this incon- 
venience, especially where the demand is not sufficient to ensure a rapid 
consumption, is a subject of much importance. Dr. A. T. Thomson has 
proposed that hydrocyanic acid should be kept in four or six ounce bottles 
diluted with water in the proportion of a drop or two to the ounce, by 
which means a fresh bottle would be opened for almost every prescription. 
This plan might answer the purpose when water is the vehicle ordered, 
but when this is not the case we have no alternative but to keep the acid 
of the medical strength, and to dispense it from a very small bottle. 
The hydrocyanic acid of Scheele contains five per cent., by weight, of 
real acid ; that of the pharmacopoeia is about two-fifths of the above 
strength. This fact unfortunately is not generally known in the profes- 
sion, and Scheele's acid having been a long time taken as the standard, is 
habitually prescribed by many practitioners. When the word "Scheele" 
is not inserted in the prescription, and the acid of the Pharmacopeia is 
employed, the patient receives only two-fifths of the dose intended, and 
the reputation of the dispenser is injured by the inefficacy of the medicine. 
♦"Organic Chemistry, in its application to Agriculture and Physiology," by Jus- 
tus Liebig, M. D. &c. 
