Pickling leather for chromium tanning - with phosphoric acid, resulting in improved chromium uptake

摘要

H3PO4 opt. mixed with another inorg. acid, pref. H2SO4, is used as acid in tanning leather, e.g. of ox, horse, pig, sheep, goat or calf, by pickling a limed, unhaired hide in an aq. soln. of an acid, followed by Cr-tanning. Pref. acid concn. in pickling step is 0.1-7 (1.5-3) wt. %/wt. hide. Wt. of H3PO4 refers to aq. soln. having specific wt. 1.75. Wt. of other acids refers to 100% concn. Wt. ratio H3PO4 : other acid is 1 : 10 to 10 : 1 (1 : 4 to 5 : 1) esp. 1 : 3 to 3 : 1. Tanned prods. having smoother grain can be obtd. by adding 4-8 wt. % inorg. salt, esp. NaCl, to pickling fluid.