December, 1912.] 



427 



THE MANUFACTURE OF TANNIN FROM 

 MANGROVE. 



The Indian Forest Records of July has an interesting article on the 

 above subject by Mr. Pcran Singh, F.C.S. 



He states that 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 mangrove bark which is also generally used by Burmese tan- 

 ners, is about Rs. 22 per ton at Rangoon. Its cost at Mergui is Rs. 15 

 per ton, the freight from Mergui to Rangoon being Rs. 5 per ton. But 

 the price of mangrove bark is liable to considerable reduction if regular 

 and large supplies are contracted for, or if the collection is methodically 

 undertaken by the manufacturer direct. The wholesale cost at Mergui 

 is Rs. 15 per ton, and it stands to reason that at this rate the dealer 

 must be making some profit after allowing for transport of the bark from 

 the forest to the market. Though exact figures at which the bark can 

 be extracted are not known, the total cost of the collection of bark per 

 ton by direct agency may be safely placed at not more than Rs. 10 

 per ton, which would work out to about Rs. 15 per ton delivered at 

 a factory near Rangoon. Besides, it has been noticed that the bark 

 merchant sells his dry and fresh bark at the same rates. Hence a further 

 reduction seems possible were the manufacturer to have his own drying 

 sheds in the forests and were the material to be air-dried before shipping. 

 Taking the moisture of fresh bark to be 50 per cent., the cost of the 

 freight per ton is reduced at once by half and the total cost is thus 

 reduced from Rs. 15 to Rs. 12'50 per ton delivered in the vicinity of 

 Rangoon. 



If the bark is to be purchased in the open market it must be done on its 

 percentage contents of tannin and moisture. Mangrove barks vary much 

 in quality, and it would be unbusiness-like to pay for good as well 

 as for bad barks at the same rate. The price of air-dried bark contain- 

 ing about 30 per cent, of tanin with a moisture content of 10 per cent, say, 

 might be fixed at the maximum of Rs. 20 per ton delivered at the 

 factory. 



Yield of Extract per 1 00 Parts of Bark. 



It has already been shown that mangrove barks of good quality should 

 at least yield 50 per cent, of solid extract containing 20 per cent, of mois- 

 ture. For purposes of estimate, however, the ratio of bark to extract 

 is taken at 2*0 : 1 instead of 2 : 1, thus allowing for the variation in the 

 quality of the bark. 



Mangrove barks when air-dried, containing 8 to 10 per cent, of mois- 

 ture, 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 ' of the total quantity of the bark 

 used. 



The total outlay of a tannin factory capable of dealing with 20 tons of 

 baik or tan woods in 24 hours is estimated at Rs. 286,500. 



