Bisulphite solubility test

In the urea-bisulphite solubility test [24], wool is treated with a solution of urea (50%) and sodium bisulphite (3%) (pH adjusted to 7) at 60 C for Ih and then the residue is washed and dried till constant weight is obtained. Urea breaks the hydrogen bonds and bisulphite attacks the disulphide bonds in wool. Solubility in this method depends on the wool which had been treated in acidic or alkaline pH. 16.11.4 Spectrophotometric test [25, 26]... 

Lees and Elsworth International Textile Wool Conference, 1955) drew attention to the fact that wool which has been submitted to an alkaline treatment has a lowered alkali solubility. To avoid this source of error the urea bisulphite test was proposed. Alkali treated wool has a lower solubility in the urea bisulphite reagent, and treatment under acid conditions brings about an increased solubility. These facts make it possible to arrive at an historical deduction of the nature of the cause of any degradation. 

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