Irangi ryibyuma ni umuryango wamabara arimo ibyuma bihujwe nigice kama.Amabara menshi ya azo, cyane cyane ayakomotse kuri naphthol, akora ibyuma bigizwe nurusobekerane rwa kimwe cya azo azote.Irangi ryuma risize irangi ryerekana irangi ryerekana isano iri hagati ya fibre proteine.Muri iryo bara, molekile imwe cyangwa ebyiri irangi ihujwe na ion yicyuma.Irangi rya molekile mubusanzwe ni imiterere ya monoazo irimo amatsinda yinyongera nka hydroxyl, carboxyl cyangwa amino, zishobora gukora ibice bikomeye byo guhuza hamwe nibyuma byinzibacyuho nka chromium, cobalt, nikel na muringa.