Lactic, citric, hydroxyacetic, and gluconic acids were found satisfactory for stabilizing iron solutions to be used for tanning leather. The influence of pH and concentration on the combination of iron (F e20 a) with standard hide powder was investigated. The maximum fixation of 23 t o 25 percent of ferric oxide occurs in t he pH range 3.5 to 4.0. Practical tanning experiments were made with goat-and calf-skins. The shrinkage temperatures of the iron-tanned leathers are lower than those of well-tanned chrome leathers. The results of accelerated a ging test s indicate that all of the iron-tanned leathers tested had at least fair aging qualities except where gluconic acid was used. The use of iron salts for replacing those of chromium in the tanning of leather shows most promise where citric acid is used for stabilizing the solutions.

The differen ces between the wearing qualities of vegetable-tanned commercial sole leathers are small, the differ ence bet ween the best and worst of the 20 tannages studied amounting to less than 16 percent. Additional compression, similar t o that given by heavy rolling, improved the wear 5 percent. The t es ts al so indicated that there is no significant diffe rence in the wear of leather t a nned from domestic and from frig orifico hides; that water-soluble material and grease are lost from soles in service, with the greatest loss being sh own by wat er-soluble ash; that the "rubber" and "leather" abrasive machines are of little use in predicting the relative wearing qualities of tannages ; and that the wat er-soluble content, firmness, and degree of tannage are useful in estimating the wearing quality. These conclusions are based on t ests in service of about 500 pairs of soles, mostly at Camp Lee, Va.