No. 3 (192 1) MANUFACTURE OF FISH OIL AND GUANO 211 



Stuffing greases are those used for giving suppleness to tanned 

 leather while at the same time rendering it water-proof and increas- 

 ing its weight; fish tallow is a regular ingredient of such greases. 



There should be considerable use for West Coast fish stearine, 

 even in India, for waggon greases and in leather working. 



MANUFACTURING PRECAUTIONS. 



105. Before discussing the modes of refining fish oil, it is neces- 

 sary, even at the cost of some repetition, to mention the evils to 

 which fish oil is subject ; then only is it possible to differentiate good 

 from inferior oils, to understand why certain things should or should 

 not be done, why certain methods should be adopted or avoided, 

 why certain precautions should be taken, how certain impurities 

 or deteriorating agencies may be minimized or removed, how such 

 methods and precautions will greatly add to the value even of crude 

 unrefined oils, and may often obviate the need for subsequent 

 refining which always adds some expense in labour, loss of oil, 

 etc., and indeed, in the case of really bad oil, may even be 

 impracticable. 



106. Characteristics offish oil. — Good fish oil should be bright and 

 clear, from pale yellow to brown in colour, of an odour which, 

 though fishy, is moderate in character, like that of good cod liver 

 oil, and of similar taste. Inferior oil is turbid, dark brown to black 

 in colour, of strong and even nauseous odour often including that 

 of taint or of scorching, and of pungent and very disagreeable 

 flavour ; if acid, it is not only sharp to the palate but is very irritant 

 to the throat owing to the action of the fatty acids on the mucous 

 membrane. While high quality fish oils are suitable for edible 

 and medicinal purposes, low class can only be used for rough 

 industrial purposes such as the tempering of steel, etc. Prices of 

 course vary with quality ; when common oil was quoted (pre-war) 

 at £14 to £16 per ton, fine yellow oil from Tanur was priced at 

 £18 to £21 in the English market. 



107. Fish oil — like other oils — is a glyceride of the fatty acids, 

 that is, it is a combination of glycerol with certain fatty acids, 

 which differ greatly according to the source of the oil. These 

 constituents of oil may be separated one from the other by 

 decomposition ; mostly by what is called hydrolysis or the action of 

 water on oil, assisted by various agencies such as bacteria, enzymes, 

 organic impurities, warmth, light, and air. Oil thus decomposed i§ 



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