human
There are many conceivable combinations, and in this section will be chiefly discussed a few which have demonstrated some commercial possibilities. Some of these have already received notice in the preceding sections. The manufacture of curried dressing leathers is a combination of vegetable and fat tannages. The manufacture of waterproof chrome uppers illustrates a combination of chrome and fat tannages. The use of
gpt
in conjunction with vegetable tanning materials is also a combination tannage. The case of chamois leather is possibly a combination of aldehyde tannage with fatty acid tannage. Two-bath chrome leather is a combination of chrome, sulphur and fat tannage. Formaldehyde and vegetable tannage is also a known possibility. It is clear that there are possibilities of endless complexity, and that what normally may appear as a simple tannage is in reality a very complex combination tannage. From this standpoint one might instructively consider the successive adsorptions involved in a goatskin tanned first with syntans, then with oak bark,