PHYSOSTIGMINE. 
§ 499-] 
4i7 
mine (first separated in 1864 by Jobst and Hesse), and possibly a second, 
according to Harnack and Witkowsky, who have discovered in association 
with physostigmine a new alkaloid, which they call Calabarine, and which 
differs from physostigmine in being insoluble in ether and soluble in 
water. It is also soluble in alcohol; and further, the precipitate pro¬ 
duced by potassium iodo-hydrargyrate in calabarine solutions is insoluble 
in alcohol. 
§ 499. Physostigmine, or eserine, is not easily obtained in a crystal¬ 
line state, being most frequently extracted as a colourless varnish, drying 
into brittle masses. It is, however, quite possible to obtain it in the 
form of partially crystalline crusts, or even rhombic plates, by care being 
taken to perform the evaporation, and all the operations, at as low a 
temperature as possible, and preferably in a dimly lit room ; for, if the 
temperature rises to 40°, much of the alkaloid will be decomposed. 
Hesse recommends that the beans be extracted by alcohol, the alcoholic 
solution alkalised by sodic carbonate, and the liquid shaken up with 
ether, which will retain the alkaloid. The ether solution is now separated, 
and acidified slightly with very dilute sulphuric acid ; the fluid, of course, 
separates into two layers, the lower of which contains the alkaloid as a 
sulphate ; the upper is the ether, which is withdrawn, and the acid fluid 
passed through a moist filter. The whole process is then repeated as a 
purification. 
Again, Yee, who has repeatedly obtained the alkaloid in a crystalline 
condition, directs the extraction of the beans by alcohol, the alcoholic 
solution to be treated as before with sodic carbonate, and then with ether ; 
the ethereal solution to be evaporated to dryness, dissolved in dilute acid, 
precipitated by sugar of lead, and the filtrate from this precipitate 
alkalised by potassic bicarbonate, and then shaken up with ether. The 
ethereal solution is permitted to evaporate spontaneously, the crystalline 
crusts are dissolved in a little dilute acid, and the solution is lastly 
alkalised by potassic bicarbonate, when, after a few minutes, crystalline 
plates are formed. 
The formula ascribed to physostigmine is C 15 H 21 N 3 0 2 . It is strongly 
alkaline, fully neutralising acids, and forming tasteless salts. It crystal¬ 
lises from benzene in large flat prisms which melt at a temperature of 
105°—106°. It dissolves easily in alcohol, ether, chloroform, and bisul¬ 
phide of carbon, but is not easily soluble in water. The specific 
rotatory power in chloroform is [u]jj = —82°. The benzoate 1 crystallises 
in hard white prisms melting at 115°-118° ; the majority of the other 
salts are very hygroscopic. 
If C0 2 is passed into water containing the alkaloid in suspension, a 
clear solution is obtained ; but the slightest warmth decomposes the 
soluble salt and reprecipitates the alkaloid. The hydrarg-Fiydriodide 
1 Petit and Polonovsky, J. Pharm., xxix. 55. 
27 
