2 
Indian Forest Records. 
[Vol. III. 
theory of preparing tannin extracts, The processes are described under 
the heads of (1) Extraction, (2) Cooling, (3) Filtration or Mechanical 
clarification, (4) Evaporation, (5) Decolonisation and (8) Mixed Extracts. 
Under the latter head “ Mixed Extracts/' arguments have been advanced 
to show, that in tropical countries at least, where forests abound in 
tanning materials of all kinds, the manufacture of mixed extracts is 
preferable to that of decolourised extracts. 
Chapter II deals with the factors that determine the quality of tannin 
extracts specially with reference to that from Mangrove bark. It has 
been shown that use of fresh bark or air-dried fresh bark, and of dis¬ 
tilled water for leaching the bark, is essential, and that, after extrac¬ 
tion, the cooling of the tan liquors and their mechanical clarification are 
necessary processes that cannot be dispensed with if a good quality of 
extract is desired. 
Chapter III gives a summary of the defects in the extracts that 
have been from time to time manufactured experimentally in Burma. 
The commercial valuation of the tannin extract prepared bv the writer 
on a large scale is also given to indicate the possibility of making a 
marketable extract from the Burma barks. 
Chapter IY deals with the percentage yields of the tannin extract 
from Mangrove barks of different species, with a conclusion that the 
air-dried barks of good quality should yield 50 per cent, of extract 
containing 20 per cent, moisture. 
The estimates of the capital outlay required for a model tannin 
extract factory together with an analysis of profit and loss of the 
manufacture of Mangrove tannin extract are given in Chapter Y. With 
an outlay of iR2,86,500 on a factory dealing with 60 tons of the raw 
material per day, there is likelihood of a net profit of 27 per cent, being 
obtained on the total capital outlay, where good tannin extracts made 
from myrabolams and Mangrove barks mixed in proportion of 1 : 6 are 
produced. The possibility of making a small concern with an output 
of li tons of extract per day, remunerative, has also been noted, the 
figures being based on those actually obtained by the writer in experi¬ 
mental manufacture on this scale. 
This note is published in the hope of creating an interest in an 
industry of a comparatively recent growth even in Europe. A statement 
of the development of trade in the tannin extracts together with a list; 
of firms dealing in tannin extracts machinery is appended. 
219 
