The effective interfacial area of glass Raschig rings (8.0 x 8.0 x 1.0 mm), for gas absorption with Chemical reaction, was measured in the range 0.1-0.6 cm /s of superficial liquid velocity and for kinematic viscosities of 1.18- 1.87 cm2/s by using the well-known Co+2 catalysed sulphite oxidation method. The aim was to study experimentally the effect of liquid viscosity on the effective interfacial area by adding different amounts of sugar to sodium sulphite Solutions. The increase in the effective interfacial area (a) was maximum 7 % only at high liquid flow rates. At Iow liquid flow rates, the gas-liquid interfacial area (a) was not affected noticeably by the viscosity of solution. It was found that the regression analysis of measured (a) values, as function of liquid flow rate and kinematic viscosity, followed the following equation: