PRODUCTION OF DYES 

 CH, 1+30- 



319 



. Aniline. Paratoluidine. 



3H 2 0+C 19 H 17 N 3 



Pararosaniline. 



The prefixes ortho and para and the numerals 1 : 2 and 1 : 4 

 introduced into the formulae refer to the relative positions in the 

 molecule of the constituents methyl, CH 3 , and amidogen, NH 2 . 

 The constitutional formulae of ortho- and para-toluidines would 

 be represented by the following diagrams, the meaning of which 

 has been already explained : 



HN 2 



Orthotoluidine. 



Paratoluidine. 



The colouring matters are each built up of three groups of 

 this kind held together by an atom of carbon. They are repre- 

 sented by the following expressions in which every group of C 6 

 must be regarded as forming a ring or closed chain of carbon 

 atoms. 



C 6 H 4 -NH 2 

 C 6 H 4 -NH 2 



C 6 H 3 (CH 3 )-NH : 



Pararosaniline hydrochloride. 



Rosaniline hydrochloride. 



There are a number of other colouring matters constructed on 

 the same type ; they are all derivable from one parent hydro- 

 carbon called triphenylmethane, the composition of which is 

 represented by the formula : 



HC-C 6 H 5 

 \C 6 H 6 



