No. 3 (1921) MANUFACTURE OF FISH OIL AND GUANO 181 



coil of copper tinned externally, through which pressure steam 

 passes; the oil from a slightly elevated tank slowly enters the 

 vessel at the bottom and as it passes upwards is strongly heated 

 by the steam coil, the vaporized moisture from the oil escaping 

 through holes in the cover, while the oil passes out by a cock and 

 pipe direct to the storage barrels or other receptacles : the process 

 is thus conducted almost automatically and without contact with 

 the air, and the oil cannot be contaminated between the feeding 

 tank and the final receptacle. But with oil prepared in a cleanly 

 manner and thoroughly washed, this process is not found actually 

 necessary at Tanur ; probably it would be useful if the oil were 

 made from tainted fish. 



73. For factories which have no steam it is easy to sterilize and 

 drive off moisture without open fire ; e.g., by placing the oil in a 

 metal vessel (e.g., in kerosine oil tins) and heating these in a bath 

 of strong brine, either an ordinary salt brine or one of calcium 

 chloride which is a cheap and readily procurable material 

 habitually used in ice factories for making their necessary brine. 

 These brines only boil at a temperature considerably above 

 212° F. according to the density of the brine ; hence the vessels 

 of oil placed in such a bath also attain a temperature which 

 drives off any suspended water; this was successfully tried 

 at Tanur before present methods were adopted. Yellow oil so 

 treated deepens very slightly in colour, and of course cannot 

 possibly scorch. The external brine bath is, of course, heated by 

 open fire: the ordinary fish boiling pan of the factory would do 

 very well in which case calcium chloride is preferable to sodium 

 chloride (common salt) in the bath since iron is practically unaffect- 

 ed by a calcium chloride brine which can be raised to a very high 

 temperature by an increase in its density, that is, by adding more of 

 the material. Of course the water lost from the brine by boiling 

 must be continually replaced. 



It is suggested that if the oil were passed slowly through a 

 spiral coil made of thin copper and of narrow diameter, which 

 traversed a trough of strong boiling brine it could be very effec- 

 tively sterilized and dried. 



PRODUCTS. 

 GUANO; 



74. Generally speaking, the solid product is that primarily sought, 

 especially in western countries where it is greatly in demand as 



