Practice of Kinetics (Comprehensive Chemical Kinetics, Volume 1)

5 THE LIQUID-GAS INTERFACE 263supported by the sample, was detected by light reflected onto a photoresistorbridge. The bridge was attached mechanically to a recorder pen and moved inresponse to the light, drawing a trace of the expansion.4.8 OTHER METHODSA number of other methods have been employed in specific systems, but theexperimental details are limited and the references will only be mentioned brieflyto indicate the possibilities.Stone and Tille~~~~have shown that the spectral changes which occur on spinelformation can be related to the extent of reaction of the component oxides, althoughthe kinetics were also followed by chemical analysis. Keyser el aL3'j7 havestudied the reaction of zirconium silicate with calcium oxide by a radio tracermethod. Wagenblast and Damask368 have used internal friction measurementsto study the rate of precipitation of carbon in iron. The rate of decrease of theSnoek peak can be related to the growth kinetics of the iron carbon precipitate36%3705. The liquid-gas interface5.1 INTRODUCTIONReaction at liquid surfaces covers a wide field. However, special experimentalmethods have been developed mainly for the study of insoluble or partly solublemonolayers at the liquid-air interface. Adsorption and reaction of monolayersat the liquid-air interface and liquid-liquid interfaces can be studied by similartechniques. It is therefore convenient to treat these together. Comprehensiveinformation about liquid interfaces is contained in publications by Adamson',Da~ies~~l, Alexander372, Davies and Ridea1373 and Gaine~~~~.Kinetics of reaction at the interface are generally studied by the same methodsas are used for the study of the monolayer itself. These are mainly the determinationof surface area (A), film pressure (n), surface potential (AV, and surfaceviscosity. A number of relationships developed by Adamson' illustrate the typeof kinetic expressions obtained for simple reactions.(1) The rate of dissolution of a monolayer into an infinite medium may bedetermined by the rate of diffusion of material away from the surface region. ThenIn (r/ro) = ~K(D~/z)+where r is the surface concentration per unit area and K is the proportionalityconstant.References pp. 270-278