gio Mr. Hatchett’s additional 'Experiments 
The second variety of the tanning substance is obtained from 
a great number of vegetable bodies, such as indigo, dragon’s 
blood, common resin, & c. & c. by digesting and distilling them 
with nitric acid. It is not, therefore, quite so readily prepared 
as that which was first described, and its relative quantity, when 
compared with that of the substance employed to produce it, is 
less. 
As resin and some of the other bodies do not afford it until 
they have been repeatedly treated with nitric acid, and as dur- 
ing each operation nitrous gas is produced, whilst the strength 
of the acid which comes over is diminished, it seems almost 
tation ; but the second and third appear to be important ; for they prove that tannin 
is principally formed, or at least deposited, in the interior white bark, which is next to 
the alburnum or new wood ; so that in the very same part where the successive portions 
of new wood are to be elaborated and deposited, we find the principal portion of 
tannin. 
It should seem, therefore, that there is an intimate connexion between the forma- 
tion of new wood and the formation of tannin in such vegetables as afford the 
latter; and this idea is corroborated when the chemical nature of these substances is 
considered. 
From experiments made on the ligneous substance of vegetables, or the woody fibre, 
it appears to be composed of carbon, oxygen, hydrogen, and nitrogen, but of these its 
principal and essential ingredient is carbon. 
In like manner carbon is unquestionably the basis and principal ingredient of tannin. 
Considering, therefore, that both of these substances consist principally of carbon, 
that tannin is secreted in that part of barks where the formation and deposition of new 
wood take place, and that the quantity of tannin is the most considerable in young 
trees, and seems therefore to keep pace with their more vigorous growth and consequent 
rapid formation of wood, it appears very probable that those vegetables which contain 
tannin, have the faculty of absorbing more carbon and of the other principles than 
are immediately required in the formation of the different proximate vegetable sub- 
stances, especially the woody fibre : that this excess, by chemical combination, 
becomes tannin, which is secreted in the white interior bark : that in this state it is 
a principle peculiarly fitted to concur by assimilation to form new wood : that it is 
therefore subsequently decomposed at the proper period, and is employed in the 
