No. 3 (1921) MANUFACTURE OF FISH OIL AND GUANO 22/ 



with plenty of boiling water, thoroughly mixed up with it and then 

 allowed to settle, the impurities will be dissolved in or mechani- 

 cally carried down by the water, this precipitation being hastened 

 if fine salt is sprinkled at intervals on the surface of the oil, the 

 salt acting mechanically in carrying down solid impurities and 

 also, by uniting with the water and thus increasing its specific 

 gravity, it promotes rapidity of separation. As noted also in para- 

 graphs 71,116, etc., supra, the oil may be very effectively washed and 

 sterilized by admitting live steam into the oil through a perforated 

 coil ; grain salt may be added after the steam is turned off. 

 Steam heating tends to volatilise the substances which give fish 

 oils their peculiar odours. 



The result of such washing is a turbid layer of water below a 

 layer of washed oil which is then drawn off by taps, syphons, etc., 

 the Florentine receiver system (paragraph 67 supra) might be con- 

 veniently adapted for this separation. The oil thus washed and 

 separated may then be boiled by steam, either by a closed coil, or 

 in a jacketed pan, or as suggested in paragraph 72 supra. 



It is stated (Lewkowitsch) that in Japan the crude sardine oil is 

 " refined " by heating it to 50" to 6o° C. (l22° to 140° F.) for an hour 

 and then running it off into wooden vessels where it separates into 

 three layers. The upper layer is liquid and clear, the middle layer 

 consists of solid fat, and the lowest layer of water intermixed with 

 albuminous substances and "scrap." Possibly the heating is by 

 open steam which would account for the layer of water, unless 

 indeed the crude oil is that which comes direct from the separating 

 tanks, containing a good deal of water and minute fragments 

 of fish. The ''stearine" is said to be about 30 per cent of the crude 

 oil. This purification is very simple but imperfect. 



Oil properly treated should, after settling, be bright and clear 

 since the causes of turbidity, viz., suspended water in very fine 

 particles and suspended organic matters, will have been largely 

 removed. The actual colour however will not be improved, except 

 that it will appear brighter because of the clarity of the oil. 



127. Clarification. — A further process may be added, viz., that 

 of rapid and complete removal of all foreign substances by clarifica- 

 tion ; this method is profitable not merely by improving the oil 

 but by greatly increasing the rapidity of purification, thus enab- 

 ling a manufacturer to use much smaller storage plant and to sell 

 II 



