Two in-situ compound from ferron sulphate and tetra hydroxymethyl phosphonium sulphate (THPS) was synthesized according to different mole ratio between the two materials. By testing the UV absorption and FT-IR spectrum of Fe-THPS compounds, the most possible mole ratio of n(Fe(Ⅱ))∶n(THPS) was 1∶3. Then the stable constant of Fe-THPS was determined by potentiometer titration. It was found that the compound is unstable, and the stability at 30 ℃ is better than that of 40 ℃. At last, sheep skin was tanned with solo FeSO4, solo THPS, FeSO4 and THPS, Fe-THPS compound. The results showed that the hydrothermal stability of leather treated with combination tannage is higher than that of leather treated with solo tanning agents, and its shrinkage temperature can reach to 90 ℃. Fe-THPS has the best cross linking property and the leather treated with the compound has a good dry thermal stability. The tensile strength and tearing strength of leather tanned with Fe-THPS compound is enhanced obviously, which can meet the request of garment light leather.
