GENERAL EVALUATION 



Classical methods have been and continue to be 

 applied to specific groups of compounds by special- 

 ists. Rigorous chemical characterization of specific 

 compounds usually requires complex procedures for 

 isolation (ion-exchange, paper or column chroma- 

 tography, fractional distillation or crystalhzation), 

 for establishment of structure (melting point, spec- 

 tral measurement, mass spectral analysis, nuclear 

 magnetic resonance, elemental analysis, and so on), 

 and for verification (degradations, preparation of 

 derivatives, and synthesis if possible). Under normal 

 circumstances these techniques are the responsibility 

 of the chemist rather than the biologist. The biol- 

 ogist is rarely personally involved in detailed 

 chemical methodology, but certain techniques such 



327 



