Continuous diazotization of amines

Azo dyes are obtained by continuous diazotization of amines (see Division C2) and further reacting by coupling the diazo compounds obtained. Examples are given in which sulphanilic acid, metanilic acid, and p-chloroaniline are diazotized and coupled with b -naphthol or 1-phenyl-3-methyl-pyrazolone-(5).ALSO:In a process for the continuous diazotization of amines and for the recovery or further reaction of the diazo compounds formed, the reactants are continuously mixed and reacted and the heat of reaction is substantially absorbed by the reaction mixture with a rise in temperature, the diazo compound formed being recovered or subjected to further reaction either with retention or elimination of the nitrogen atoms, e.g. to form azo dyes, hydrazines, phenols or diazonium salts. Specified amines are primary monoamines and polyamines of aromatic character derived for example from benzene, condensed ring systems with 2 to 4 benzene nuclei to which heterocyclic rings may be anellated, heterocyclic compounds and derivatives thereof which contain side chains and/or inert substituents such as carboxylic, sulphonic, hydroxyl, amino and nitro groups, and halogen atoms. Diazotizing agents specified are solutions of nitriles in acids, nitrous acid esters or nitrosyl compounds. Two types of apparatus are described for carrying out the process. Examples are given for the diazotization of sulphanilic acid, metanillic acid, p-chloroaniline and aniline, and for the reduction of the diazo compounds to give hydrazines.