154 ANNUAL REPORT SMITHSONIAN INSTITUTION, 194 5 



Several methods for preparing drinking water from sea water on 

 life rafts were in a partial state of development. However, no method 

 approached practicability for life-raft use even though available infor- 

 mation intimated as much. In fact, few investigators realized that it 

 was a long step from the successful employment of a method under the 

 ideal conditions of the laboratory by skilled laboratory technicians 

 to its use under the trying conditions on a life raft by an inexperienced 

 individual. Those responsible for the evaluation of the various sug- 

 gestions and devices pertaining to survival at sea soon realized how 

 little knowledge was available and how much had to be learned about 

 the entire problem. 



Several methods for producing potable water from sea water had 

 reached a state of development sufficient to merit consideration for 

 life-raft use. The first four methods described below are based on 

 physical devices for producing potable water. 



1. The Visscher body still. — This still consisted essentially of a 

 vacuum pump to reduce pressure in the system and of a small boiler 

 strapped about the body to utilize body heat for fuel to distill fresh 

 water from sea water. Condensation of the water vapor was achieved 

 by immersing a coil and collecting bottle in sea water. 



The still had much in its favor, though the disadvantages out- 

 weighed the advantages. It required the expenditure of a significant 

 amount of muscular energy to maintain the reduced pressure; in 

 northern latitudes, a partially fasting individual could ill afford to 

 lose the body heat required for the evaporation of the water. Sec- 

 ondly, considerable machine tooling and engineering were involved 

 in the production of a special vacuum pump which was to be subjected 

 to the corrosiveness of sea water The weight and volume ratios 

 (water produced per unit of weight or of volume occupied by the 

 apparatus) were very poor. Finally, the loss of any one part made 

 the still useless. 



2. Safety fuel still (2). — "Canned heat" was used as fuel to distill 

 the sea water and the cool sea water was used to condense the water 

 vapor. The smallest model of this still, though possibly suitable for 

 large lifeboats, was much too bulky and heavy for life-raft use. Fur- 

 thermore, the still was affected by wind, wave, and rain as well as the 

 corrosiveness of sea water. Considerable manipulation and intelli- 

 gence were required for operation and, contrary to available data, the 

 still did not produce enough water on a weight-volume ratio to recom- 

 mend its use. It had many more parts than did the Visscher still so 

 the possibility of the still becoming inoperable through loss of a part 

 was greater. 



3. Armbrust cup (3). — This method differed but little from a 

 method developed during the last war, whereby the moisture of the 



