182 ANIMAL PROTEINS 



6 hours. An hour or more in a hydraulic press removes 

 superfluous liquor and some more grease. The fleshes are 

 separated, cooled and then stocked for 30 minutes to equalize 

 the moisture in them. After removing from the stocks 

 they are sprinkled on both sides with cod oil and thrown 

 back into the stocks for a few hours. They are then dried 

 cold for a day or two. The stocks used are similar to those 

 once popular for softening dried hides during soaking, and 

 consist of two heavy hammers which fall alternately upon 

 the goods which are contained in a curved box below. The 

 result is a mechanical kneading action. The fleshes are 

 again sprinkled with cod oil, restocked for a few hours and 

 dried again, this time at 100 F. They are then repeatedly 

 sprinkled, stocked and dried, the last operation being 

 conducted always at an increasing temperature until finally 

 the final " heater " is even up to 160 F. As the operation 

 proceeds it is advantageous to hang the splits also nearer 

 one another, and in the final " heater " they are quite close. 

 The next stage is to pack the goods quickly into suitable 

 boxes and allow them to " heat," i.e. to oxidize further. This 

 is a rather critical stage in the process, and to prevent over- 

 heating (" burns ") it is often necessary to open out and 

 repack into another box, with possibly some little intermediate 

 cooling. They are turned over thus repeatedly until the 

 oxidation is complete, and then spread out to cool. 



The fleshes are now a dark brown colour, and are next 

 treated to remove excess of oxidized oil products. The 

 goods are dipped through water at 110 F. and then subjected 

 to hydraulic pressure. The grease and water which exude 

 are ah 1 owed to separate by settling, and the thick yellow oil 

 so obtained, known as " degras," forms a valuable material 

 for leather dressing, as it more readily emulsifies with water 

 than many oils, and impart this quality to other greases 

 mixed with it. A further quantity of a similar oil is obtained 

 by paddling the goods with a weak soda solution. The liquor 

 obtained is treated with sulphuric acid to neutralize the 

 alkali, and the grease recovered is known as " sod oil." The 

 fleshes are now well washed with hot water (140 F.), fat 



