518 Prof. R. Meldola on the Theory of the 



general view of their characters, so as to gain a clear notion 

 of all the conditions whicb have to be fulfilled by any proposed 

 formula. These characters are summarized below, those com- 

 pounds containing similar radicals being spoken of as "normal" 

 compounds, and those containing dissimilar radicals as "mixed" 

 compounds : — 



(1) Normal compounds are prepared by diazotizing an 

 amine, X . NH 2 , and acting with the diazo-salt upon another 

 molecule of the same amine, X . NH 2 , or, what amounts to the 

 same thing, one molecule of nitrous acid may be made to act 

 upon two molecules of X . NH 2 . 



(2) Mixed compounds are obtained by diazotizing an amine, 

 X . NH 2 , and acting with the diazo-salt upon one molecule of 

 another amine, Y . NH 2 . The same compound results if the 

 order of combination is reversed. 



(3) The diazoamido-compounds, both mixed and normal, 

 contain one atom of hydrogen easily replaceable by metals 

 and alkyl radicals. If the aromatic radicals contain strongly 

 acid groups (such as N0 2 ), the resulting diazoamido-com- 

 pounds may be distinct monobasic acids. 



(4) Normal compounds are resolved by acids into their 

 constituents, the diazo-salt and amine. 



(5) Mixed compounds are resolved by acids into a mixture 

 of the two bases from which they are derived, and a mixture 

 of the two diazo-salts corresponding to these two bases. 



(6) Alkyl derivatives of normal compounds may be pre- 

 pared in two ways: — 



a. By the action of a diazotized amine, X . NH 2 , upon 

 the alkylamine of the same base, X . NHE. 



/3. By the direct alkylization of the normal diazoamido- 

 compound. 



(7) The alkyl-derivatives of normal compounds are decom- 

 posed by acids into their constituents, the diazo-salt and 

 alkylamine. 



(8) Alkyl- derivatives of mixed diazoamido-compounds are 

 formed by the direct alkylization of these compounds (see 

 group 2). 



(9) Another group of mixed alkyl-derivatives can be pre- 

 pared by the action of a diazotized amine, X . NH 2 , upon the 

 alkyl-derivative of a dissimilar amine, Y . NHR. These com- 

 pounds are isomeric with those of the preceding group. 



(10) Mixed alkyl-derivatives of group (8) are resolved by 

 the action of acids into a mixture of the two diazo-salts and 

 the two alkylamines. 



