ON THE VOLATILITY AND SOLUBILITY OF CANTHARIDIN. 299 
It must also be admitted that the heat ordinarily employed in 
making the blistering cerate of the United States Pharmacopoeia, 
does not injure the preparation by volatilizing the cantharidin, 
and that the recommendation to digest the flies in the melted 
vehicle on a water bath is not only not injurious, but decidedly 
advantageous, as it increases, many fold, the solvent power of 
the fatty matter. 
2d. Having ascertained the solvent powers of olive oil, oil of 
turpentine and acetic acid, on pure cantharidin, the following 
experiments were made with those menstrua, and with water, on 
the flies in substance : 
a. One hundred grains of powdered cantharides were mixed with 
two hundred grains of olive oil in a large test tube, which was 
corked, and the mixture heated in a boiling water bath during four 
hours, with occasional agitation. The contents of the tube were 
then poured into a small glass displacement apparatus, surrounded 
with water kept hot by a lamp, and the saturated oil gradually 
displaced, without cooling, by the addition of fresh portions of oil. 
The oily liquid thus obtained had a deep green color, smelled 
strongly of the flies, and when applied to the skin produced full 
vesication in about twelve hours contact. After standing twenty- 
four hours shining needles of cantharidin gradually separated, but 
not in quantity. 
b. One hundred grains of powdered flies were mixed with two 
hundred grains of pure oil of turpentine in a closed tube, heated 
in a boiling water bath four hours, and displaced while hot as in 
the preceding experiment. The terebinthinate solution had a dull 
yellow color, and was perfectly transparent as it passed, but in a 
short time numerous minute stellated crystals commenced forming, 
which increased in quantity by standing. The saturated cold solu- 
tion, separated from the crystals after standing twenty-four hours, 
did not blister when applied to the skin. 
c. One hundred grains of powdered flies were digested in a close 
vessel, at the temperature of boiling water, in three hundred grains 
of acetic acid sp. gr. 1.041, for six hours, and then subjected to dis- 
placement in the hot filter above noticed. A dark reddish-brown 
transparent liquid passed, which had very little odor of flies, even 
when a portion was exposed until the acetic acid had nearly all 
evaporated. A portion of this liquid applied to the skin produced 
complete vesication in about ten hours. After standing a few 
