MISBRANDING OF LEATHER. 13 



erly prepared, tanned, and finished, and that oak bark makes a 

 bright-colored leather, demands light, uniformly colored sole leather. 

 The wearer of shoes also prefers leather with a good, clear, even 

 color. 



To secure the higher price which this much-desired unifomnity, 

 brightness of color, and the appearance of oak-tanned leather brings 

 the leather is bleached. Solutions of soda and sulphuric acid applied 

 successively, oxalic acid, or oxalic acid and tin chlorid are the chemicals 

 with which this is usually done. The treatment removes some of the 

 excess tanning material from the surface and gives the leather a 

 much lighter color. Bleaching is especially detrimental, as the 

 sulphuric acid is rarely completely neutralized and consequently 

 greatly hastens the rotting of the leather. The cost of the leather is 

 increased by this procedure; the serviceability of the leather is 

 decreased; and the superior appearance secured in this way permits 

 the fraudulent sale of the leather at a higher price. The bleaching of 

 heavy leather is the most useless and harmful of all leather-making 

 practices, and the most vigorous efforts should be made to eliminate it. 



MISBBANDING OF LEATHER. 



Formerly all sole leather made in this country was tanned with 

 oak or hemlock bark or a mixture of the two, and the leather so tanned 

 was known as oak, hemlock, and union (oak and hemlock), respec- 

 tively. More leather is tanned now with quebracho than with oak, 

 and more with quebracho, mangrove, myrobalan, gambier, and 

 chestnut, collectively, than with hemlock. Nearly half of the 

 vegetable-tanned leather made in this country is tanned with 

 materials other than oak and hemlock bark. Nevertheless, practi- 

 cally all vegetable-tanned leathers are still termed oak, hemlock, or 

 union. 



The figures in the table (pp. 16 to 20) show that many of the leathers 

 are misbranded as to tannage. The tannin-free watr extract from a 

 leather tanned with chestnut oak is fluorescent when made faintly 

 alkaline. It will be seen that the water solubles from some of the 

 so-called oak leathers are not fluorescent; these leathers were not 

 tanned with chestnut oak. The figures for water-soluble materials also 

 show that many of these leathers were tanned with tanning materials 

 other than oak or hemlock bark. Tanning liquors made from nearly 

 all materials now used in this country, such as oak, hemlock, and 

 mangrove barks, chestnut and gambier extracts, and myrobalan, 

 contain approximately 2 parts of tannin to 1 part of nontannin, 

 not including in the nontannin the sugars which the materials contain, 

 which are fermented to acids and do not, therefore, add directly to 

 the weight of the leather. Quebracho extract, on the other hand, 

 contains approximately 7 parts of tannin to 1 part of nontannin. 



