90 American Fisheries Society 



given in Tables I and II, that of the spiny dogfish shows 

 considerable variation, especially in the iodine number. 

 Thus Thomson and Dunlop 1 obtained an iodine value of 

 126.4, and 8.4 per cent, unsaponifiable matter. I found 

 the iodine value to be 116.1 in one case and 142.7 in an- 

 other, and 2.65 per cent, unsaponifiable matter. The oil 

 should be studied further to characterize it fully, par- 

 ticularly with regard to the volatile and soluble acids. 



Lewkowitsch 2 states that the dogfish "is caught on the 

 coast of Oregon, Washington and British Columbia in 

 large quantities. One hundred livers are stated to yield 

 6 to 8 gallons of oil. The oil is not generally kept sep- 

 arate from cod liver oil, and is sold in admixture with 

 the latter for currying purposes." Dogfish liver oil care- 

 fully prepared may well be used for other than the above 

 purpose. 





SPINY DOGFISH BODY OIL. 



The oil in the body of the dogfish is retained exceed- 

 ingly tenaciously, and steaming under pressure does not 

 seem to be wholly satisfactory. Pressing in the contin- 

 uous screw presses yields a soft mushy product from 

 which it is difficult to obtain a good yield of oil. Extrac- 

 tion by solvents is being tried at some plants now in 

 operation for the manufacture of fertilizer and oil. 



By extraction of the dry flesh with ether I obtained a 

 brown oil with the following constants :— iodine number, 

 128.3; saponification number, 182.4; acid number, 1.66; 

 density at 30° C, 0.9176 ; viscosity at 50° C, 0.1766. The 

 oil is of lower quality than the liver oil, although its dry- 

 ing power is fully as great as indicated by the iodine 

 absorption value. 



SPINY DOGFISH EGG OIL. 



The utilization of dogfish eggs for the tanning of lea- 

 ther is dependent on the quality of the contained oil. 



'Chemical Technology of Oils, etc. Vol. II, p. 370. 

 'Ibid. p. 368. 



