30 
THE TANNINS. 
various tannin materials, ventured to repeat the conclu¬ 
sion of the older chemists that we have but one tannin, 
and that the differences are due to the other materials 
with which they are associated in the plant. It is true 
that one is often led, during the practical study of the 
subject, to ask whether we have more than one tannin 
or not, but this question is being answered as the study 
into the constitution of the various members is prose¬ 
cuted. No doubt some relationship governing them 
exists, just as there is among the sugars, but as yet it 
has not been made out, and the study will necessarily 
be a long one, since there are so many individual tan¬ 
nins to be investigated. The problem will undoubtedly 
be worked out by a study of the derivatives, and this 
by means of bromine and acetyl has been well com¬ 
menced on the gallotannic and quercitannic acids. We 
must keep in mind that a number of the individual 
tannins will be proved to be identical, as has been 
shown to be the case with sumac and a few others in 
regard to gallotannic acid, but with the great majority 
our present knowledge leads to the belief that a rela¬ 
tionship only is to be worked out. 
In general it may be said that the tannins are used 
in medicine, in the manufacture of leather and ink, and 
as a mordant in dyeing, but the special properties of 
the different members adapt them to a great number of 
minor uses. By far the largest amount of tannin is 
used in an impure state,—that is, in the form of an in¬ 
fusion or decoction, or as an extract, made by concen¬ 
trating these solutions. 
