Wursters red

The typical transformation of all p-phenylenediamine derivatives by oxidising agents in acid solution consists in a change into a salt of the quinonediimine series. The dye just observed, so called Wurster s red , was long regarded as a simple quinonimonium salt  

however, already appeared improbable when the (colourless) chloride of the simple quinonediimine became known (Willstatter). 

At this point the oxidation stage of quinonediimine has been fully reached its (very unstable) salts have scarcely any colour. The production of colour only takes place when quinonoid and benzenoid systems are present together. The molecular union of the two substances at different stages of oxidation produces the intense absorption which is a prerequisite for the formation of a dye (Willstatter and Piccard). This union need not take place in the proportion 1 1, which obtains in the present case. The relations between quinhydrone and quinone-quinol are quite similar (p. 314). 

In both cases the linkage between the molecules is labile and does not involve normal valencies. In general, molecular compounds are considered to be systems which are held together by the excess residual affinities of the components, by the mutual attraction of the molecular fields of force. 

Willstatter s theory covers not only the class of intermolecular partially quinonoid (meriquinonoid) salts it also provides a satisfactory conception of the true quinonoid dyes. The same principle, ex- 

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By electrolysing carbonate and bicarbonate solutions in the ppm range, (Borutzky et al. 2006) no (using MIO anodes) and negligible (using BDD anode) disinfection activity was measured after adding the electrolysed solution to suspensions of microorganisms. Electrolysis samples analysed by DPD test showed low radical formation ( Wursters Red ) so that a small amount of radical formation is likely. 

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