No. 3 (1921) MANUFACTURE OF FISH OIL AND GUANO 1/9 



after the fluid has risen above the level of the interstitial space at 

 the bottom of the partition ; the water is then removed as before to 

 another tanii. Of course in all cases the water passing off from 

 the receiving tank or pit contains a good deal of oil since the 

 separation is imperfect, much of the oil remaining still in suspen- 

 sion in the water; hence further separation is necessary. 



There are other methods, though not practised at Tanur at 

 present and not on the Florentine separator system ; see for 

 instance, the methods mentioned in paragraph 33 supra. 



70. The general American system, however, as mentioned above, 

 seems to differ from these, viz., in building tanks (or pits) in series, 

 and probably of some depth so as to contain the largest quantity 

 of fluid with the smallest surface ; these tanks gradually fill and 

 during this filling most of the oil separates from and lies above 

 the water; when the tank is full the top stratum, mainly of oil, 

 overflows the lip of the receptacle and passes into a similar tank 

 or series of tanks where the process is repeated. Since oil is 

 lighter than water the top stratum in the first tank is mainly oil with 

 some water; in the second tank it is oil with very little water, till, 

 at the end of the series, very little water remains. 



71. But though oil and water separate rapidly as regards bulk 

 quantities, there is always a certain amount of water in very minute 

 form, suspended in the oil, and this separates very slowly and with 

 difficulty by mere gravity ; the cloudy, turbid appearance of the 

 freshly separated oil shows the presence of water, and when such 

 oil is stored in tall tanks for some weeks a considerable quantity of 

 dirty water will be found at the bottom. It is this dirty water 

 which causes hydrolysis and acidity, etc., of oil not thoroughly 

 cleared of all water, and thus brings loss to manufacturer and 

 consumer, the latter objecting to purchase not only acid (or even 

 rancid) oil which is unfit for many industrial purposes, but to buy 

 dirty water instead of oil. Moreover this water contains organic 

 matter which also assists the hydrolysis. Hence further action is 

 necessary and it is here (as in other matters) that Tanur practice 

 should be followed. The separated oil is thoroughly washed with 

 clean hot water, and if the water is salt (e.g., sea water) so much the 

 better, since the salt is antiseptic, and since such water is of 

 greater specific gravity than fresh water, it separates more rapidly 

 from the oil. Grain salt or similar substances sprinkled slowly and, 

 gradually on the surface of the oil, are also used as clarifiers ; these 



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