The results of this investigation may be briefly summarized as follows:

(1) Ortho toluidine may be easily converted into its sulphonic acid in which the sulphonic acid group is in the position meta to the methyl group.

(2) Para toluidine is converted into a mixture of two isomeric sulphonic acids of which the one with the sulphonic acid group in the position meta to the methyl group is obtained in a ten per cent yield.

(3) Ortho toluidine sulphonic acid may be easily diazotized using sodium nitrite and concentrated hydrochloric acid.

(4) The diazo compound is very stable.

(5) The diazo compound is easily decomposed with n-butyl alcohol, the hydrogen reaction taking place.