Ionic activity products surface precipitation

The rate of fixation of the monochlorotriazinyl dyes is very much slower. The result is that there is abundant opportunity for the normal acid dyeing mechanism to give uniform distribution of the dye molecules before they become permanently anchored by covalent bond formation. It has been found that, for some unknown reason, cationic surface active compounds tend to reduce skitteriness, if a non-ionic compound is also present to prevent the precipitation of the cation-dye complex. In order to prevent foaming which can become troublesome the addition of a silicone antifoaming product has been recommended. 

The rate-determining step is therefore thought to be reaction between SaO and its conjugate acid HS2O3 the eventual product is colloidal sulphur. At an ionic strength of 0.035 mol 1 , the activation energy is 15.93 0.1e kcal mol and the frequency factor 1.64( 0.13) x 10. The rate of subsequent formation of elemental sulphur is a function of the surface area of that sulphur which has already precipitated. In acid solution dithionates decompose thus ... 

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