^14 NOTES ON THE IDENTIFICATION 



Atropine is best crystallised from alcohol, when it forms a confused 

 mass of prisms, each of an independent tint. Where the film 

 is thin, it forms fan-shaped crystals. Without the selenite, 

 the crystals merely appear a bluish white (Fig. 19). 



Strychnine crystallises from alcohol in long prisms ; from benzine 

 in polygonal plates, or six-sided prisms, not constant ; from 

 ether in dendritic forms, and sometimes prisms. Deposited 

 from chloroform, the appearance is highly characteristic, 

 forming rosettes, and various forms of great beauty. I have 

 made no attempt to delineate the rosette with any approach 

 to accuracy, as it is scarcely possible to copy it in pen and 

 ink. It is probably too familiar to my readers to need des- 

 cription. I have succeeded in obtaining a film of strychnine, 

 quite invisible with ordinary illumination. On introducing 

 the polariser, dark circular forms and ridges are made visible. 

 When the selenite plate is added, the most gorgeous colours 

 are obtained. 

 I regard the appearance of strychnine as so characteristic as to 

 obviate the necessity of using chemical tests. I have frequently 

 extracted the alkaloid from organic mixtures, and identified it in 

 this way without the trouble of purification from dirt. Of course 

 I presuppose the absence of other substances that can enter into 

 combination. There is only one other alkaloid that can, by any 

 cJiance^ be mistaken for strychnine, and that is santonine ; but, in 

 following Dragendorff's scheme, they would be extracted by 

 different solvents. Besides, there is a considerable difference in 

 the appearance when carefully examined (Fig. 20). 



Cantharidine crystallises from chloroform and from alcohol in 

 right-angled four-sided prisms. Those crystals which de- 

 polarise without colour give clear tints with the selenite, 

 showing the evenness of their surfaces. There is a tendency 

 to form stars ; the larger crystals are coloured without the aid 

 of the selenite. The appearance is quite characteristic and 

 can be confounded with no other alkaloid I have as yet 

 examined (Fig. 21). 



Brucine Sulphate is best crystallised from water. The crystals 

 depolarise chromatically without the selenite. The free base 



