Tanning animal hides - using powdery mixt. contg. trivalent chromium cpd. and magnesite acid binder contg. magnesia and lime

摘要

Powdery mixt. for tanning animal hides contains =1 trivalent Cr cpd., in a quantity corresponding to 3-35% Cr2O3 in combination with 0.5-25% magnesite, contg. 60-90 (70-86)% MgO and 0.6-15 (2-5)% CaO. Magnesite acid-binder is opt. combined with other acid-binders. In an example, 100 pts. wt. powdery extract, prepd. by drying basic Cr sulphate and reaction prods. of hexavalent Cr cpds., and which contained 25% Cr2O3 having basicity 33%, was mixed with 6 pts. wt. powdery magnesite contg. 3.5% CaO and 85% MgO. Mixt. is a self-basifying Cr extract. No basifying or neutralising reactions take place between Cr cpds. and magnesite in absence of water. Basicity of Cr cpds., in transport or storage is unchanged. In use, basifying rate is even, alkali capacity of magnesite is used up and tanning is accelerated.