WEARING QUALITIES OF SHOE LEATHERS. 
Table 9. — Change in glucose content after wear. 
21 
Original glucose content. 
Number of 
lots. 
Number of lots showing 
loss in— 
Heel seats. 
Balls. 
17 
17 
11 
15 
Here again the results obtained for the belting leathers are very 
interesting, since the leathers mentioned in Table 9 originally con- 
tained only traces of glucose. The average gain in glucose for the 
heel seats is 0.83 per cent and for the balls 1.24 per cent. 
These results suggest a change in the leather or in some of its 
component parts with age. The most plausible explanation would 
seem to be a slow hydrolysis of the tannin and related nontannin 
materials, promoted possibly by the alkaline condition of the soils 
in the sections of the country where the shoes were worn. 
Water Solubles. 
As is to be expected from the review of the epsom salts and glucose 
results, the water-soluble materials show a general tendency to 
increase in the heel seats and balls of the worn soles (Table 10). 
Table 10. — Change in water solubles content after wear. 
Original water solubles content. 
Num- 
ber of 
lots. 
Number of lots 
showing gain 
Heel 
Balls. 
Less than 20 per cent 
Between 20 and 25 per cent 
Between 25 and 30 per cent 
More than 30 per cent 
The three lots of belting leathers which originally contained less 
than 20 per cent of water-soluble material show an increase, aver- 
aging 1.89 per cent for the heel seats and 4.78 per cent for the balls 
of the worn soles. It seems reasonable to conclude that the increase 
in water-soluble materials was due to the absorption by the soles of 
salts from the dry alkali soil where the shoes were worn. 
Uncombined Tannin. 
The uncombined tannin varies but little between the original and 
worn leathers, the differences being almost always within the limits 
of analytical error. There is, however, a consistent tendency for 
the uncombined tannin content of both the heel seats and balls to be 
slightly lower than that in the original leathers. 
