26 



INFLUENCE OF FOOD PRESERVATIVES ON HEALTH. 



that the quality of tin was so poor that a single can could only be used 

 from three to five times. It proved more advantageous to have cans 

 made to order of heavy tinned copper. The usual stock tin flange and 

 caps, however, were still employed. 



Before being used the cans were weighed, and after the collection 

 of the feces a second weight was taken. The can was then placed in 

 the water bath shown in the accompanying cut, attached to a vacuum; 

 the water was heated to approximately the boiling point, and a brisk 

 current of air was drawn through the can. It was at first feared that 

 a loss of ammonia would result from heating at this temperature, and 



FIG.- 1. Apparatus for drying feces: a, Section of can; b, water reservoir; c and d, tubes for preserving 

 constant level of water in bath; e, e, valves regulating water supply for reservoir; /, overflow pipe 

 for water bath. 



wash bottles containing sulphuric acid were placed in the circuit imme- 

 diately under the can. The amount of ammonia so collected, however, 

 was so small as to appear negligible. 



The cans were placed in the bath each morning about 9 o'clock, and 

 heated for twent}^-four hours, when they were usually dry. In some 

 cases a longer period of drying was found necessary. The dried sample 

 was then ground to a fine powder and left in an unstoppered bottle for 

 a period of four days to attract the normal amount of moisture from 

 the air. Samples for the separate determinations were weighed within 

 as short a space of time as possible. The determinations described 

 under food were then made, and by the same analysts. 



