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MADRAS FISHERIES BULLETIN 



VOL. XIII, 



94. The following characteristics of menhaden, of Japanese 

 sardine and herring oils, and of Malabar sardine oil, may be useful 

 for reference and comparison, and as guides in practical work: — 



Specific gravity is remarkably low in the Malabar oil. 



" Saponification value " represents the number of milligrams of 

 potassium hydroxide (caustic potash) required to saponify one 

 gram of oil : this is of importance in soap making. 



The "iodine value " is of great technical importance : to a great 

 extent it indicates the drying character of the oil and its suitability 

 or otherwise for lubricating and burning : a high iodine value is 

 unsuitable for edible oils and usually means a strong flavour, and 

 so on. Fish oils are of high iodine value, being only surpassed 

 (among ordinary oils) by linseed, the best of drying oils ; olive, 

 cotton seed, gingelly, and ground-nut oils range between 80 and 

 IIO ; palm, mowah and iluppai between 55 and 65 ; and butter fat 

 is as low as 35. The fish oils as shown above range from 156 to 

 187, but it is stated that yellow Japanese fish oil may be as low as 

 100 (Lewkowitsch). 



The " acid value ", i.e., the amount of free fatty acids as shown 

 by the number of milligrams of potassium hydroxide necessary to 

 render the oil neutral, is of much importance, since it indicates the 

 degree of decomposition of the glyceride, that is, the whole oil, 

 into glycerine and free fatty acids. "If oils and fats are left in 

 contact with putrescible or fermentible matter, the amount of free 

 fatty acids may rapidly increase and rise to 70 or even to lOO per 

 cent as in the case of old palm oil. The importance of the acid 

 value lies, therefore, in the fact that it indicates the quality of an 



