Abstract

An investigation has been made of the use of formic acid, or lactic acid, or binary blends of these with each other, or with sulphuric acid, in place of sulphuric acid used alone for acidifying the warm circulator vegetable tan liquors. In each case the pelt had been pretreated in a standing pickle consisting of Calgon and sulphuric acid. Small differences due to the organic acids were noted, in particular increased water absorption but improved resistance to water penetration, when formic acid was used. However, there seemed to be no advantages in the use of lactic acid. Blends of acid tended to give results intermediate in effect between the use of the individual acids. In any event the effects noted were generally very small, and this may be the result of the relatively small amount of acid used for acidifying the tan liquors, since the pickle is the major source of acid in this tanning system.