568 



u. 



S. BUREAU OF FISHERIES 



200 pounds of crushed dry ice should be thrown over the top of the 

 load. (Handle quickly with a shovel or dry cotton gloves.) The 

 door should be sealed with a strip of putty or a rubber tube against 

 all facings. The bunker hatches and the brine vents in the bunkers 

 should be closed tight. Do not open the car, once it is closed, until 

 it reaches destination. 



One of the reasons for preferring a well-filled car of fish when dry 

 ice is used is, for one thing, that it reduces cost, for no more dry ice 

 is needed for a full car than one-half full, whereas with ordinary 

 ice it is usually unsafe to pack the car entirely full. Another reason, 

 however, is not so obvious. A pound of dry ice produces 8 cubic 

 feet of gas. In an empty car of, say, 2,000 cubic feet capacity, 2,000 



Fig. 23. — Frozen steclhead in refrigerated hold of a steamer from Pacific coast 

 ports to New York, via Panama Canal. For transoceanic shipments the boxes 

 must be strapped 



pounds of dry ice will fill the car eight times with gas; that is, the 

 gas will be changed eight times as the ice evaporates. If half the 

 space is occupied with fish, the gas will be completely changed 16 

 times; if the car is seven-eighths occupied by fish, the cold gas will 

 be changed 64 times, insuring a cold atmosphere in the car at all 

 times. 



Carbon dioxide ice may also have possibilities in the refrigeration 

 of individual packages of fresh or frozen fish, oysters, and other 

 perishable sea foods. Its dryness and cleanness are desirable proper- 

 ties for this purpose and make possible the use of paper or fiber con- 

 tainers for express or even parcel post. At the present writing, how- 

 ever, though numerous trial shipments have been made, one is unable 

 to speak with confidence as to its ultimate usefulness in this field. 



