A study of fast reactions in three nozzle reactors of the same geometry has been investigated. The nozzle reactors are 0.55 x 10 ̄3 m3 1.52 x 10 ̄3 m3 and 5.13 x 10 ̄3 m3 respectively, and flow visualizations have been studied by injecting a tracer into the inlet and at the walls of the reactors. A mathematical model which has been developed, suggests that the flow characteristics in the systems consisted mainly of a series of continuous stirred tanks (CSTR1' s) with a plug flow between them, and a parallel stream of a plug flow. Fast reactions studies involving aqueous solut­ions of sodium carbonate (Na2Co2) and sulphuric acid (H2SO4) were carried out at varying molar ratios and flow rates in 0.55 x 10 ̄3 m3 and 5.13 x 10 ̄3 m3 nozzle reactors respectively. The product samples were determined volumetrically; the yield of the product and the amount of the excess acid reacted in each reactor were determined from stiochiometry. A modified residence time distribu­tion model was developed with the designed equations for a CSTR and plug flow to determine the conversion of the limiting reactant concentration. Neutralization reaction was carried out involv­ing Linear alkyl sulphonic acid (Dodecylbenzene sulphonic acid) with aqueous solution of sodium carbonate and at varying viscosity of the surfactant in 0.55 x 10 ̄3 m3 nozzle reactor. Studies were conducted at varying flow rates of Dobanic acid and sodium carbonate, and the percentage of the active detergent was analyzed volumetrically.