Part IY.J Pttran Singh : Preparation of Tannin Extracts. 3 
The writer desires to take this opportunity of expressing his best 
thanks to Professor W. R. Dunstan of the Imperial Institute, London, 
Dr. Gordon Parker of the Leather Trades Laboratories, London, Profes¬ 
sor W. R. Procter of Leeds University, and Messrs. C. Rogers, Conser¬ 
vator of Forests, Pegu Circle, and H. B. Anthony, Divisional Forest 
Officer, Depot and Agency Division, Rangoon, for the help received from 
them in this investigation. 
CHAPTER I. 
A Resume of the Process of Tannin Extract Manufacture. 
The principle of the manufacture of Tannin Extract is very simple. 
The tan wood or bark is reduced to a form suited for extraction by means 
of special machinery adapted to the requirements of the material 
treated, and the extract is then evaporated in vacuum pans to a solid 
form. 
Extraction. —The extraction is carried out in the open, using either a 
system of wooden vats, or under pressure in a battery of closed copper 
autoclaves. The latter seem to possess little advantage over the former 
except that they offer facilities for extraction on a very large scale. 
According to the experience of tannin extract manufacturers, the 
“ leaoh-ing ” of the material in open wooden or copper vats gives better 
results than close autoclaves under pressure. The following advantages 
have been indicated by Messrs. Dumsney and Noyer 1 in favour of 
open wooden vats :— 
(1) The quantity of steam required is not more, if not less, than 
what is required for a battery of autoclaves. 
(2) The battery of wooden vats is absolutely safe. 
(3) The initial cost of putting in a battery of wooden vats is lower 
and such requires less repair than a battery of autoclaves, 
where the pressure of the liquid demands special and costlj 
piping which is soon liable to leak. 
(4) The management of a battery of wooden vats is simpler and 
more systematical. 
i 
See Wood Products. Distillates and Extracts by P. Dumgney and J. Noyer, p. 185. 
220 
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