This method is intended for determining the effect on the colour of a dye, of dyeing in the presence of hexavalent chromium salts. It is applicable to wool. An alternative method is specified in 6.3 to provide a milder test suitable for assessing the effect of chromium salts in such concentrations as might be found when shading.
The difference in colour between dyeings made with and without potassium dichromate is assessed with the grey scale.
For detail please click here;-http://www.dfmg.com.tw/member/standard/bs/BS-z01.HTM