220 MADRAS FISHERIES BULLETIN VOL. XIII, 



with steam heating ; this would be useful. The Tanur method, 

 after preliminary separation of the bulk of the dirty water, as 

 detailed, is to pour the oil-cum-water into tall metal separators and 

 then to wash the oil thoroughly with boiling water poured through 

 perforated sieves at the top of the separators. Grain salt is also 

 sifted in for several reasons ; first, the salt grains carry down 

 impurities entangled in the oil; secondly, proteid matters are more 

 soluble in weak saline solutions than in fresh water, so that they 

 are more readily dissolved by the salt water; thirdly, the specific 

 gravity of the water is materially increased by adding salt, so that 

 the salt solution separates more rapidly from the oil; to some 

 extent also the salt absorbs suspended moisture from the oil as it 

 passes through it. The separators are made tall in comparison 

 with surface area to increase the depth and narrow the superficial 

 area of the two fluids and thus facilitate the drawing off, by cocks 

 at various heights, of the respective quantities. The washed oil 

 can subsequently be heated in a special heater by a closed steam 

 coil if so desired, in order to drive off any remaining suspended 

 moisture, but this is not usually found necessary; the process will 

 be mentioned under " refinement. " 



It has not been usual to filter the oil at Tanur, but a small filter 

 press was obtained for the purpose, and a filter vessel for ordinary 

 upward filtering was made but was only used for brine filtering : 

 see below s.v. " filtration. " 



1X8. The ordinary coastal factories do not properly attend to 

 separation, which is conducted with insufficient speed or thorough- 

 ness; there is no washing of the oil which, as elsewhere shown, is 

 simply heated in a pan over an open fire in order to sterilize and 

 drive off any remaining water, the process being imperfect and 

 causing loss by the carbonization of the oil and of impurities which 

 are not subsequently washed out. 



Hence it is advisable to have a series of settling pits of small 

 size and of considerable depth in proportion to area and provided 

 with means — 



(1) for rapidly separating the oil and water which should 

 preferably be made saline ; 



(2) for rapidly passing on the partly separated oil from pit to 

 pit, automatically if possible on the principle of the Florentine 

 receiver (see paragraphs 67 — 69) ; 



