Sequential oxidative and reductive bleaching

Regarding the first approach vast amount of information is available on thiourea [39-43] and the reaction mechanism can be represented as  

Despite the advantages of using thiourea to induce in situ reductive bleaching, some potential users of single bath processes hesitate to use it due to the toxic nature of thiourea. Furthermore, thiourea though easily handled and thoroughly consumed, is classified as carcinogen unlike its oxidised counterpart, thiourea dioxide (formamidinesulphinic acid). 

Trithiocyanuric acid (TTCA s-triazine-2,4,6-trithiol) is a cyclic analog of thio- 

Thiourea Sodium salt trithiocyanuric acid (Na TTCA) 

6 Bleaching of wool with emulsion of hydrogen peroxide 

---