22 BULLETIN 1168, U. S. DEPARTMENT OF AGRICULTURE. 
NONTANNINS. 
As would be expected from the increase in glucose and epsom salts, 
the nontannins show a tendency to be greater in the worn parts of 
the leathers, except in those cases where the original leathers contain 
high percentages of nontannins. 
Hide Substance and Combined Tannin. 
The results from the hide substance and combined tannin deter- 
minations also show a general tendency to be lower in both the heel 
seats and balls of the worn soles than in the unworn leather. This 
would follow from the absorption of soluble materials by the soles. 
Acidity. 
Without exception the acidity is lower in the balls of the worn 
soles than in the unworn leather, and in all but 8 out of 37 lots the 
results indicate that the leather was alkaline in reaction after wear. 
This is undoubtedly due to the nature of the soil in the region where 
the shoes were worn. 
SUMMARY. 
The experiments reported in this bulletin were conducted in a 
region having a very dry climate and " alkali" soil. Results obtained 
under such conditions may not and in some cases probably will not 
hold for leather worn in humid climates. Army types of leather and 
shoes, worn under Army service conditions, were used for the tests, 
so that the comparisons and conclusions here indicated may not 
apply to the ordinary kinds of leather and shoes subjected to civilian 
wear. Although the results of these experiments can not be con- 
sidered final, they are significant indications which, because of the 
large number of samples involved, may be accepted until additional 
data are obtained. Wear experiments, while offering the best 
opportunity to obtain valuable information, also present many 
difficulties, so that final conclusions from a single series of tests are 
seldom justifiable. 
Upper leathers. — From the standpoint of durability, all types of 
upper leather were satisfactory when the short life of sole leather is 
considered. None of them showed signs of being nearly worn out 
at the close of the experiments. Retanned chrome leather was the 
best in pliability and softness, that with the grain finish being slightly 
better than that with the flesh finish. Bark-tanned upper leather 
was the least satisfactory in appearance and pliability, 58 per cent 
of the uppers made from this leather being rated as too stiff and hard. 
Soling materials. — Fiber soles of the kinds used were not suitable 
for the conditions of wear, owing principally to the fact that as soon 
as the soles had worn down through the stitches they frequently 
ripped or broke off. Imperfections, such as ripping, bulging, chipping, 
and breaking, were numerous in the fiber soles. When these failures 
did not develop, however, the fiber soles wore well, being rated second 
in wear. Such imperfections were negligible in the leather soles. 
Types of shoes. — That certain features in the construction of the 
shoes played an important part in their serviceability is strongly 
indicated by the excessive toe wear frequently found during this in- 
