The product distribution of a fast chemical reactions introduced by Bourne in 1987 was used to study mixing on T-jets reactors under different operational parameters and for different geometries. The Bourne´s test system was the reaction between 1-naphthol and diazotized sulfanilic acid. The results obtained for the mixing characterization study on T-jets using the Bourne´s test system showed that the Reynolds number has a great influence on the mixing degree. Moreover, the geometrical parameters of T-jets also influenced the conversion of Bourne’s test reactions. With increasing of ratio between the width of inlet jet and width of mixer chamber, the quality of the mixing is increasing. Another important operational parameter is the ratio of flow rates between the jets, which was also proved in this work to have a critical influence on mixing.