REFRIGERATION OF FISH 



575 



who also precooled the fish either in a cool room or in cool brine con- 

 taining about 6 per cent salt held at 27° to 30°, after which pre- 

 cooling they were frozen in a tank of saturated brine at a low tem- 

 perature — about 5° F. above zero. The brine was refrigerated by 

 a cooler outside the freezing tank. Henderson also used a charcoal 

 filter for purifying the brine after it had been in use. 



All these inventions, appearing to be essentially the same thing, 

 failed to come to practical application, and all the patents have ex- 

 pired except that of Henderson. It is not difficult to understand 

 w r hy these inventions failed. It is easy to demonstrate the freez- 

 ing of a few fish quickly in a tank of very cold brine, the quantity 

 of which is large in proportion to the amount of fish to be frozen, 

 and the quality of the goods frozen in such a demonstration is easily 



Fig. 26. — Brine freezer similar in principle to Rouart's, used for freezing smelt 



at Seattle, Wash. 



apparent. It is by no means so easy, however, to freeze 25,000 to 

 100.000 pounds of fish a day, w<ash them, glaze, pack, and store when 

 open tanks of brine are used, the fish being frozen singly, wet with 

 brine, curled, and misshapen. 



DAHLS METHOD 



The first brine-freezing method to be put into practice was that 

 of Nekolai Dahl, 40 a fish merchant of Trondhjem, Norway. 



The fish are packed in the containers in which they are to be 

 shipped. A cover, with holes, is fitted on the box, and the boxes 

 are stacked on a mass of cracked ice and salt in a chamber or hold 

 of a vessel. A suction pipe is provided in the bottom of the cham- 



40 U. S. Patent 1123701, Jan. 5, 1915; Danish Patent 18S44, 1914; British ^Patent 

 13760, Mar. 6, 1912. 



