20 
BULLETIN 1168. U. S. DEPARTMENT OF AGRICULTURE. 
cent for the heel seats and for the other a loss of 0.19 per cent, 
cause of these increases is unexplained. 
The 
Epsom Salts. 
The epsom salts content is calculated from the total magnesium 
present in dilute-hydrochloric-acid-soluble form in the ash of the 
leather and is not limited to the quantity that may have been present 
as magnesium sulphate. 
The epsom salts content of all lots of vegetable-tanned sole leather 
shows an average increase in the worn soles of 0.21 per cent for the 
heel seats and an average decrease of 0.34 per cent for the balls of 
worn soles. The heel seats of 11 lots and the balls of 19 lots show 
a loss of epsom salts. The change in epsom salts content corresponds 
somewhat to the epsom salts content of the original leather, as is 
shown by the results in Table 8. 
Table 8. — Change in epsom salts content after wear. 
?' 
Original epsom salts content. 
Between — 
and 2 per cent 
2 and 3 per cent 
3 and 4 per cent 
4 per cent and over . 
Number of 
lots. 
Number of lots showing 
loss in — 
Heel seats. 
Balls. 
The epsom salts content of the soles cut from the belting leathers 
is interesting in that these leathers were originally almost entirely 
free from magnesium. The increase during wear in magnesium, cal- 
culated as epsom salts, is nearly 1 per cent on the average. Consider- 
ing that the soil in the section where the experiments were conducted 
alkali soil," this increase in magnesium is readily explained. 
is 
Glucose. 
While an increase in the magnesium content of worn soles might 
be expected under certain conditions of wear, a similar increase in the 
glucose content could hardly be expected. Yet of 34 lots of vege- 
table-tanned sole leather, 23 show a gain in glucose in the heel seats 
and 20 show a gain in the balls of the worn soles. The increase in 
the heel seats ranges from 0.12 to 1.32 per cent and in the balls from 
0.03 to 1.82 per cent. The average shows for the heel seats a gain 
of 0.32 per cent and for the balls a loss of 0.05 per cent. 
To guard against unduly high glucose results, due to the influence 
of magnesium and possibly other salts, many of the glucose deter- 
minations were checked by Low's volumetric method for determining 
the copper in the reduced cuprous oxid. The difference between the 
glucose results obtained by the two methods was not sufficient to 
account for the gain in glucose through contamination of the cuprous 
oxid. 
