ABSORPTION SPECTRA OF THE ALKALOIDS. 
521 
This is explained by the absorption bands being caused by the compactness of 
structure of the nucleus of the molecule, and that equal weights are not molecular 
weights, so that by substituting the hydrogens of the nucleus by radicals which 
exert no selective absorption, the result is a reduction in the absorptive power of a 
given weight of the substance. Examples are afforded by morphine and codeine 
(methyl-morphine), diacetyl-codeine and tetra-acetyl morphine. 
3. Bases which contain oxyclised radicals, as hydroxyl, methoxyl, and carboxyl, 
increase in absorptive power in proportion to the amount of oxygen they contain. 
This is exemplified by papaverine, narceine, narcotine, and oxynarcotine. The apo- 
derivatives are less diactinic than the parent bases. Examples are apo-morphine 
and pseudaconitine. 
