Part IV.] Puran Singh : Preparation of Tannin Extracts. 29 
The tannin values of these barks range between 24 and 37. These 
have been carefully determined not only by the hide powder process, but 
by the nickel hydroxide process, the figures obtained by which are in 
close agreement with those given in the table. 
It is rather difficult to determine the colour measurements with abso¬ 
lute accuracy. But the observations recorded in the above table were 
made under similar conditions and the figures may, therefore, be taken 
as approximately correct. They are not of much assistance in enabling 
any nice distinctions to be drawn between the colour of the old and the 
young bark, but they clearly show that the extracts from the bark of 
Rhizophora mucronata , whether old or young, and those from Ceriops 
Candolleana would give extracts of deeper colour than those of Rhizo- 
phora conjugata and Bruguiera gymnorhiza barks, whether old or young. 
Yield of Extract per ioo parts of Bark. 
The above table shows that the mangrove barks when air-dried, 
containing 8 to 10 per cent, of moisture, yield 50 per cent, of extract, 
containing 20 per cent, of moisture. 
A lower yield than this shows that either leaching is not thoroughly 
done or the quality of the bark is below the standard. 
From fresh bark containing 40 per cent, of moisture, the yield of the 
extract with 20 per cent, water will be |rd of the total quantity of the 
bark used. 
CHAPTER V. 
The Estimates of Profit and Loss of the manufacture of Mangrove 
Tannin Extract in Burma. 
Before considering the estimates of profit and loss of this industry, 
it seems desirable to give a general idea of the conditions under which 
it should be started. 
The Raw Material .—The raw material is fairly abundant in Tavoy 
Mergui and Andaman Isles. If the Mangrove forests are worked in 
scientific manner, the supply may be said to be almost inexhaustible. 
The current market rate of the Mangrove bark which is also generally 
used by Burmese tanners, is about R22 per ton at Rangoon. Its cost 
at Mergui is R15 per ton, the freight from Mergui to Rangoon being 
R5 per not. But the price of the Mangrove bark is liable to considerable 
24 $ 
