Gelatine. Tannin. Azote.
Hemlock 60.4 39.6 10.88
Sumac 60.4 39.6 11
Pine bark 52.5 47.5 9.56
Quebracho 57.1 42.9 10.4
Chestnut 53.97 46.03 9.79
Oak 55.87 44.13 10.24
Laurel 60.4 39.6 10.94
Oak, 3 years in vat 58.75 41.25 10.65

It is not pretended that these figures are absolutely correct, as they
often vary in certain limits even for similar products. They form,
however, a fair basis of calculation.

As to whether leather is a veritable combination, it seems to us that
this question should be answered affirmatively. In fact, the resistance
of leather properly so-called to neutral dissolvents, argues in favor of
this opinion.

Furthermore, the perceptible proportion of tannin remaining absorbed by
a like amount of hide is another powerful argument. It remains for us to
say here that the differences observable in the quantity of fixed tannin
ought to arise chiefly from the different natures of these tannins,
which have properties differing as do those of one plant from another,
and which really have but one property in common, that of assimilating
themselves with animal tissues and rendering them imputrescible.

In conclusion, these researches determine the functions of resinous
matters which frequently accompany tannin; they show a very simple
method for estimating the results of one's work, as well as the degree