Techniques based on the Lewis cell

The simplest device providing rudimentary control of hydrodynamics is the Lewis cell [ 19 ], of which a variation by the present author is easier to construct. It consists of a reactor containing two contra-rotated agitators positioned on either side of a liquid-liquid interface, Fig. 5.16. 

The present author has used the method to obtain an approximate rate constant for the oxidation of an arylhydrazine with oxygen, and to show that the reaction occurred in film . A saturated solution of the hydrazine in an aqueous sodium chloride solution was reacted 

This technique is not applicable in cases where the concentration of the reacting component in the receiving phase can be expected to be depleted in the diffusion film, since the range over which the mass transfer coefficient can be varied is too small to permit meaningful extrapolation. The necessary conditions for the acquisition of second-order rate constants in the case of a fast in-film reaction have been discussed [15]. 

Interfacial processes can only be studied in the flat interface stirred cell in cases when there is no depletion within the diffusion film, and when there are no complicating surface adsorption effects. 

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