No. 3 (1921) MANUFACTURE OF FISH OIL AND CUANO I65 



subjected to powerful hydraulic pressure rising to 2,000 lb. per 

 square inch ; the oil so obtained is called " winter oil " because it 

 does not deposit stearine even in winter. 



The amount of stearine thus separated is not stated, but in 

 case of sperm and probably whale oil, the percentage of clear 

 winter oil obtained by this process seems to be from 67 per cent if 

 pressed at 32^ F., to 75 per cent if pressed at 38° F. Hence the 

 proportion of solid stearine (plus " foots " or stearine-cum-impurities) 

 seems to be from 25 to 33 per cent, or from one-fourth to one-third. 



40. The clarification and bleaching of the oil are variously 

 effected, but the usual plan is by admixture with caustic soda, or 

 even with soda ash if the oil is acid (contains free fatty acids) at 

 212'' F., or somewhat lower. This causes the formation of a soap 

 which usually entangles most of the suspended impurities, while 

 the heavier impurities are precipitated ; on removal of the soap 

 scum and decantation from the "foots," a clear, bright oil is 

 obtained ; the process not only clarifies but to some extent bleaches. 

 A cheap and effectual method of bleaching is by exposure of 

 shallow layers of the oil in wide shallow tanks to the influence of 

 the sun ; the layers of oil may be from 3 to 12 inches deep, and 

 the effect seems to be increased, and dust kept out, by covering the 

 tanks with a glass covering ; this process is said to result in a 

 clear light straw colour. But it should be noted that very little, if 

 any, bleaching is needed if the oil has been niade rapidly by the 

 use of steam from fresh fish: "extra light crude" (A grade) 

 requires little but clarification : on the other hand, intrinsically 

 bad oil, made by inferior processes from tainted fish, and possibly 

 scorched by open-fire methods, cannot be effectively treated though 

 it may be somewhat improved, by any process commercially 

 practicable. 



The soap and foots resulting from the refining processes is sold 

 at from I to 2 annas or thereabouts per pound, so that the process 

 is not wasteful. 



41. The oils thus trccited are sold as "extra bleached winter 

 fish-oil," " bleached winter fish oil," " light winter fish oil," and 

 "brown winter fish oil." The higher class oils are used for 

 illuminating, lubricating, and painting, and, down to light brown 

 for leather currying ; the dark oils are only used for tempering 

 steel and other metal "working. The finer oils are said to 

 be better than even linseed oil in the way of standing weather, 



