After the furs have been treated with the solution of some alkali for the purpose of killing the hair, they are always passed through a slightly acidulated bath to remove any alkali which may still be adhering. This operation must always be gone through before the skins can be mordanted or dyed, for if it were neglected, very uneven and uncertain results would be obtained. This process, however, entails the expenditure of no small amount of time, labor and chemicals when large lots of skins are being handled. In order to eliminate this extra step of “souring” between killing and mordanting or dyeing, it has been proposed to use alkaline mordants which combine the killing and mordanting functions, and accomplish these two processes at the same time. The advantages of employing such mordants are easily apparent. Cumbersome manipulation and handling of the skins, with the attendant consumption of much time and labor are reduced to a minimum, and besides there is no needless waste of chemicals as is the case in the ordinary methods of killing the furs. The principle of alkaline mordants is not a strictly new one. If it be remembered that the old killing formulas used by the fur dyers of an earlier age, contained metallic salts with mordanting properties in addition to the alkaline substances, which alone were effective as killing agents, it would seem that the suggested alkaline mordants were merely a revival in modified form of the old processes. This is undoubtedly true in a large measure, for the killing mixtures which the old masters used certainly embodied the fundamental principle of simultaneous killing and mordanting, although it was not recognized at that time. Modern alkaline mordants have therefore been devised which can be employed for killing and mordanting furs at the same time. They are prepared as follows: ALKALINE ALUMINUM MORDANT 250 grams of potassium alum are dissolved in 1 liter of boiling water. To this solution is added 300 grams of soda ash, previously dissolved in 750 c.c. of water, and the resulting precipitate is filtered off, washed and pressed, and then dissolved in a solution of 65 grams of caustic soda in 1 liter of water. ALKALINE CHROMIUM MORDANT 250 c.c. of chrome acetate mordant of 20 degrees Beaumé 320 c.c. of caustic soda solution of 38 degrees Beaumé (32.5%) 10 c.c. of glycerine 30 degrees Beaumé (95%) The solution of these substances is brought up to a volume of 1 liter by the addition of 420 c.c. of water. ALKALINE IRON MORDANT 138 grams ferrous sulphate are dissolved in 362 c.c. of warm water. Cool and add 25 c.c. of glycerine. Then slowly and carefully add 25.5 c.c. of concentrated ammonia, taking care that no precipitate forms.