14 
Indian Forest Records. 
[Vol. III. 
CHAPTER II. 
Factors that determine the Quality of Tannin Extracts with special 
reference to Mangrove Bark Extract. 
The quality of the tannin is chiefly determined by the following 
factors :— 
(1) The quality of the larlc.— The fresher and sounder the bark or 
the tan wood, the better is the quality of the resulting extract. If the 
hark is exposed for any length of time to atmospheric oxidation, the 
tannin contained in it is oxidized, resulting in a darker colour. Much of 
it becomes insoluble owing to the formation of insoluble products. Bark 
dried in the sun undergoes similar changes and its original percentage of 
tannin is considerably reduced. Mangrove bark when sun-dried becomes 
dark and hardened by the deposit of oxidation products in the fibre with 
the result that it yields its tannin with difficulty in the process of 
diffusion. 
It is therefore necessary to always secure fresh barh for extraction. 
This can only be possible if the central factory is situated close to the sources 
of supply; if this is not feasible, the bark before despatch should always be 
air-dried in the shade and exposed in separate layers , in well-ventilated 
sheds. This can he effected in commodious, airy store sheds erected 
specially for this purpose near the forests and equipped with wooden 
platforms in which to store bark until dry. 1 The hark when thus dried 
retains about 8 to 10 per cent, of moisture and is very much less liable to 
deterioration during transit to and storage in the central factory, than 
when freshly collected. 
As regards the tan woods, the opinion of Messrs. Dumsney and Noyer 
(.Dumsney and Noyer loc. cit ., page 128) may he cited. They urge upon 
the extract manufacturers to require of the suppliers of tan wood 
(chestnut wood), the delivery of sound wood and ask them to reject rotten 
and ferruginous wood as incapable of a normal yield of tannin. The effect 
1 See also Schlich’s Manual of Forestry, Volume V (Forest Utilisation), pages 49^ 
and 499. 
