I62 MADRAS FISHERIES BULLETIN VOL. XIII, 



separation. The first tank is usually large and deep, so that the oil, 

 water, and impurities may have a considerable time to separate ; by 

 the time this is full the upper stratum will be mostly oil, and this 

 stratum then flows over the upper edge of the tank into a smaller 

 tank, which consequently contains mostly oil with some admixture 

 of water; the process is repeated till, after passing several tanks, 

 the fluid is almost free from water and impurities except a certain 

 amount of both still suspended in a very minute form. 



32. While it is necessary to separate the oil from the original 

 water and impurities as quickly as possible — especially in hot 

 weather — to prevent fermentation and hydrolysis, it is nevertheless 

 equally necessary, for this very purpose, to wash the oil thoroughly 

 with fresh water. In the American factories the various separating 

 tanks are provided with perforated steam coils and water, and the 

 oil which flows into them is thus submitted to the action of steam 

 jets which, by their agitation, thoroughly wash the oil with pure 

 condensed water. The washed oil is then allowed to settle and is 

 separated in the usual way. 



33. The water is removed from the various tanks by a simple 

 arrangement on the principle of a Florentine receiver or vase, and 

 is commonly called the " coffee-pot " which such vase resembles. 



Another means of separation is that of a swivel pipe by which 

 a short pipe jointed to a main pipe by means of a swivel, can be so 

 set as to remove the stratum of oil, either by a pump, or by gravity 

 if the tank levels permit, at any distance below the surface without 

 disturbing the water stratum below the oil. Or a pipe with funnel 

 mouth is fixed in the bottom of the tank and communicates with a 

 lower tank ; the funnel piececan be set at any height and when the 

 pipe is open allows the fluid to be drawn off from any level to the 

 lower tank where the oil which may still be suspended in it, 

 separates in the usual way. 



If the several tanks can be placed on different levels, the receiv- 

 ing tank being at the highest level and others in steps below it, 

 the oil and water can conveniently be run off by gravity without 

 the aid of pumps. 



34. The tanks are mostly provided at the bottom with steam 

 coils so that the fluid may be kept at a temperature of about 

 125° F. : this keeps fluid the whole oil and the stearine, a some- 

 what solid fat which accompanies the oil, and also tends to more 

 rapid separation of the oil and water, 



