The chemical absorption rate (RA) of CO2 was measured into the aqueous nanometer sized colloidal silica solution of 0-31 wt% and diethanoleamine of 0-2 kmol/m(3) in the flat-stirred vessel with the impeller size of 0.034 m and its agitation speed of 50 rev/min at 25 degrees C and 0.101 MPa, and compared with the values estimated from the model based on the film theory accompanied by chemical reaction. The value of the volumetric liquid-side mass transfer coefficient (k(L)a) of CO2, which was used to estimate the value of R-A, was obtained by the empirical correlation formula presenting the relationship between k(L)a and the rheological behavior of the aqueous colloidal silica solution. The value of R-A in the aqueous colloidal silica solution was decreased by the reduction of k(L)a due to the elasticity of the solution.