CHEMICAL MICROSCOPY 



The traditional tests on the well-known 

 alkaloids are made on aqueous solutions. 

 About 80 substances, mostly natural alka- 

 loids, or of natural origin although syntheti- 

 cally modified, have been studied repeatedly 

 by different investigators for their reactions 

 in such tests. Table 1 summarizes the data 

 for 16 of these with the 11 reagents which 



give most of their major aqueous micro- 

 crystal tests. 



These reagents are equally applicable to 

 numerous other alkaloids. It is luifortunate 

 that publication of the isolation of a new 

 plant alkaloid is almost never accompanied 

 by some individual or highly characteristic 

 analytical test by which subsequent investi- 



a, amorphous precipitate, not crystallizing 



c, crystals form, either directly or from an amorphous precipitate 



a(c), amorphous precipitate, crystallization poor or uncertain 



c(a), normally crj^stals but precipitate may remain amorphous 



ac, discrepant reports, usually because of variations in reagents or because crystallization, while 

 fairly certain, is quite slow 



(a), (c), or (ac), amorphous precipitate or crystals may not form in most tests because of lack of 

 sensitivity 



— , no result 



C, major crystal tests 



1-6, Figures. 



14 



