Source—Reactant as Microphase

Two important situations can be identified in this category (1) reactant is a sparingly soluble solid and (2) reactant A is present both as large and fine (micro) bubbles of gas. The latter involves dissolution of gaseous A in phase 2 in the form of macrobubbles accompanied by enhancement of the rate by microbubbles of A and is not considered here. Case 1 is developed below. 

Because the solubility of B is very low in the situation considered, the reaction plane tends to coincide with the macrointerface (x = 0). This implies that now the rate is controlled only by the diffusion and dissolution of B. For this to happen, the condition 

When solid dissolution is unimportant, we have a situation where absorption of A may be deemed to occur in a solution saturated with B. This is identical to regime 14.4 described in Chapter 14, and Equation 14.24 is recovered. 

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