844 BOTANY AND PHARMACOGNOSY. 



Physostigmine Salicylate (CisH^iNgOo.QHeOs). 



Occurrence : See p. 439. 



Physostigmine (or eserine) forms from solutions in benzene 

 rather large crystals having a M. P. of 105-106 C. The salts 

 of physostigmine are quite easily decomposed and not easily 

 crystallizable. The benzoate, salicylate and the double salt 

 formed with potassium-mercuric-iodide yield, however, good 

 crystals. The salicylate of physostigmine usually occurs in 

 needle-like crystals or large prisms, one part at 25 C. being solu- 

 ble in 72.5 parts of water; 12.7 parts of alcohol; 8.6 parts of 

 chloroform; and 175 parts of ether. From solutions in chloro- 

 form single crystals may be obtained which vary in length from 

 0.4 to 1.5 mm. (Fig. 189) ; large characteristic aggregates are 

 also formed. The crystals are easily decomposed and best kept 

 in a desiccator. 



Physostigmine Salicylate. Crystals from solutions in 

 chloroform. 



Orthorhombic : a: b: c = 0.869 : i : f . 



Forms observed: Base (001); macropinacoid (100); 

 brachypinacoid (010); unit prism (no). 



Angles: Angle iioAiTo = 82. 



Habit: Tabular on the base, elongated along the a axis. The 

 crystal is terminated by the macropinacoid or the unit prism. 

 The latter form may possibly be actually a pyramid, but this 

 cannot be definitely decided upon owing to the thinness of the 

 crystals on which it occurred. In the majority of cases the 

 crystal is terminated simply by the pinacoid with the corners 

 and faces more or less rounded as if by re-solution. The in- 

 dividuals are usually grouped in radiating aggregates. 



Optical properties: a=6; i}=a; t=c. The axial plane is the 

 macropinacoid. Bxa=c. Optical sign +. The apparent 

 angle 2E, between the optic axes, is not large, so that both axes 

 may be observed in the interference figure seen on the base. 

 Certain individuals are in such a position on the slide that the 

 interference figure shows the emergence of one optic axis, and 



f 



i 

 I 



i 



