PURPOSE: To enable tanning of leather with a chromium liquid almost completely extracted in a specific configuration by using the chromium tanning liquid that is basified through a prebasifying process in the presence of aldehyde or keto-acid.
CONSTITUTION: When leather that was acid washed with formic acid and/or sulfuric acid is tanned by use of a chromium (III) salt that is 0.5-12 wt.% of the leather weight, a tanning liquid is prebasified by a basifying agent in the presence of aldehyde and/or keto-acid to set its pH at 3.6-4.3, and is then basified using an alkali aluminum silicate to set the pH at 4.2-5.5. The prebasification of the tanning liquid is carried out using a basifying agent that is 0.3-0.7 wt.% of the leather weight, in the presence of 0.3-4.0 wt.%, preferably 0.5-2.0 wt.% aldehyde and/or keto-acid of the leather weight.
EMIIRU RUSHIYAINSUKII
RUDORUFU TSUAUNSU
