Distribution of Cr (III) and Cr (VI) in chrome tanned leather

Basic chromium sulphate is the most versatile and common tanning agent in the leather industry. Under certain circumstances, the oxidation of the trivalent chromium salts into the hexavalent compounds, which are used in leather manufacture, is a crucial issue. In this study, different proportions of basic chromium sulphate were used in tanning and re-tanning processes according to a commonly used recipe, and levels of chromium oxide and hexavalent chromium were studied stratigraphically in the cross-section of the leather. It was observed that the levels of chromium oxide and hexavalent chromium in the skins increased in relation to the proportions of basic chromium sulphate used in the process, and that the amounts added in the tanning process had a greater effect on the levels of hexavalent chromium formed in the layers of the skins than did the amounts added in re-tanning.