WEARING QUALITIES 01 SHOE LEATHE] 19 
Total \\i> [nsolublb Ash. 
The total ash content of the balls of the worn soles is decidedly 
higher than that of the original leather; that of the heel seats is 
but slightly greater. 
The soluble ash content of the heel seats of the vegetable-tanned 
leathers, with the exception of the lot containing barium chlorid, 
increased on an average 0.26 per cent and the insoluble ash content 
increased 0.07 per cent, making the gain for total ash equivalent to 
0.33 per cent. Both the soluble and insoluble ash contents are 
decidedly higher in the balls of the worn soles, being 1.11 and 1.19 
per cent, making the increase for the total ash equivalent to 2.3 per 
cent. Only four lots show a loss in total ash for the heel seats, 
and this loss is very slight, the greatest being 0.17 per cent. The 
balls of the worn soles in no case show a loss in total ash. 
Three of the seven lots of chrome-tanned leathers show a slight 
increase in the total ash of the heel seats, and four show a slight 
decrease, making the average a loss of 0.1 per cent. The balls of the 
worn soles of all chrome-tanned lots show an average gain in total 
ash of 4.19 per cent, despite the comparatively high ash content of 
the original leathers. 
Chromium Oxid. 
The chromium oxid content of the chrome-tanned leather remains 
practically constant, showing a tendency to only a slight decrease in 
the worn soles. 
Petroleum-Ether Extract. 
The petroleum-ether extract results are not as consistent as the 
ash results. The grease content of the heel seats and balls of the 
worn soles, however, shows a general tendency to increase. There 
are indications that the grease content of the worn leather reaches an 
equilibrium which may differ for each leather or kind of leather. 
The petroleum-ether extract in sole leathers containing -1 per cent 
or more shows a consistent tendency to decrease on wearing. This 
is particularly noticeable in the case of Lot 25 which was highly oiled. 
the losses for this lot being 4.02 per' cent for heel seats and 4.69 per 
cent for balls. Xine of the vegetable-tanned sole leather lots show 
loss of grease from the heels seats, and six show a loss from the balls 
of the worn soles. The average increase in the petroleum-ether 
extract of the 34 lots of sole leather is 0.39 per cent for the heel seats 
and 0.53 per cent for the balls. Omitting lot 25, these results become 
0.53 and 0.(59 per cent. 
As compared with the sole leathers, the belting leathers are high in 
petroleum-ether extract, and all three lots show a loss in both heel 
seats and halls, the average being LSI and 3.22 per cent, respectively. 
In two lots the loss is slight, and it would seem that it is not entirely 
in proportion to the original oil content. 
All the waxed chrome-tanned sole leathers show losses in petroleum- 
ether extract, the average being 2.16 per cent for the heel seats and 
11.10 per cent for the balls. The losses For the heel seats vary from 
0.58 to L46 per cent and those i'ov the balls from 2.77 to 22.52 per 
cent. 
The unwaxed chrome-tanned sole leathers show an increase in the 
balls of 3.40 and 1.45 per cent, and for one lot an increase o( 0.41 per 
