8 LEATHEK INVESTIGATIONS I SOLE LEATHERS. 



Well-tanned, honestly-made leather should approach the upper 

 rather than the lower limits for leather substance and oils and fats. 

 The water-soluble constituents should consist only of the materials 

 contained in the adhering tanning solution which have not been 

 removed in scouring. 



Properly air-dried sole leather should not contain, even in very 

 damp weather, more than 20 per cent of moisture, and the average 

 percentages for the year should fall below 15 per cent. Neither the 

 ultimate buyer nor the shoe manufacturer should be called upon to 

 pay for a greater average amount than this. It will be observed that 

 the leathers reported herewith contain much less moisture, due largely 

 to the fact that they dried out very much after reaching thelaboratory. 



Normal vegetable-tanned sole and harness leather when burned 

 should not leave more than 1 per cent of ash and as a rule not more 

 than 0.5 per cent. This ash is derived from the hide, from the 

 lime used in unhairing, and from the salts usually dissolved in all 

 waters. The magnesia of the ash when calculated to Epsom salts 

 (MgSO 4 + 7H 2 O) , the form present in air-dried leather, should not 

 exceed 1 per cent. 



It is customary abroad to consider less than 2 per cent of glucose 

 permissible, the assumption being that this amount may be present 

 from the tanning materials. It is very doubtful if this amount of 

 glucose is ever present in normal leathers from which the excess of 

 tanning materials has been properly washed. Leathers on which the 

 final liquors were sweet and exceptionally concentrated, and which 

 are subsequently washed but little, may contain between 1 and 2 per 

 cent of sugars, determined as dextrose. 



The ether extract or fat may be as high as 5 per cent, probably 

 never much less, to give pliability, water resistance, and durability to 

 the leather. 



WEIGHTING OF LEATHER. 



During an extended examination of sole leathers now in progress, 

 it has been found that a surprisingly large percentage contains great 

 quantities of foreign materials. Although it has long been known 

 that some tanners make a practice of weighting or loading their 

 leather, the extent of the practice is not appreciated outside the 

 tanning and closely related industries. Tanners state that leather is 

 loaded with foreign materials because the boot and shoe makers will 

 buy only the lower-priced leather, which, to use a trade expression, 

 "cuts to advantage," that is, from which the greatest number of soles 

 can be cut at the lowest cost a pair. Many boot and shoe manufac- 

 turers claim that they use loaded leather because it cuts to better 

 advantage than the same leather not loaded. 



The character, value, and wearing quality of leather varies with 

 the part of the skin from which it is made. The skin from the upper 



