22 



CALORIMETERS FOR STUDYING RESPIRATORY EXCHANGE, ETC. 



By means of a hand microphone and receiver, the subject can communi- 

 cate with the observers outside at will. A push-button and an electric bell 

 make it possible for him to call the observers whenever desired. 



HEAT-ABSORBING CIRCUIT. 



To bring away the heat produced by the subject, it is highly desirable 

 that a constant flow of water of even temperature be secured. Direct con- 

 nection with the city supply is not practicable, owing to the variations in 

 pressure, and hence in constructing the laboratory building provision was 

 made to install a large tank on the top floor, fed with a supply controlled 

 by a ball-and-cock valve. By this arrangement the level in the tank is 



maintained constant and 

 the pressure is therefore 

 regular. As the level of 

 the water in the tank is 

 approximately 9 meters 

 above the opening in the 

 calorimeter, there is am- 

 ple pressure for all pur- 

 poses. 



The water descends 

 from this tank in a large 

 2-inch pipe to the ceiling 

 of the calorimeter labora- 

 tory, where it is subdi- 

 vided into three 1-inch 

 pipes, so as to provide 

 for a water-supply for 

 three calorimeters used 

 simultaneously, if neces- 

 sary, and eliminate the 

 influence of a variation 

 in the rate of flow in one 

 calorimeter upon the rate of flow in another. These pipes are brought 

 down the inner wall of the room adjacent to the refrigeration room and part 

 of the water circuit is passed through a brass coil immersed in a cooling- 

 tank in the refrigeration room. By means of a by-pass, water of any degree 

 of temperature from 2° C. to 20° C. may be obtained. The water is then 

 conducted through a pipe beneath the floor to the calorimeter chamber, 

 passed through the absorbers, and is finally measured in the water-meter. 

 A diagrammatic sketch showing the course of the water-current is given 

 (fig. 14), in which A is the tank on the top floor controlled by the ball 

 cock and valve, and a is the main valve which controls this supply to the 



Fig. 14. — Schematic diagram of water circuit for heat-absorbers of 

 calorimeter. A, constant-level tank from which water de- 

 scends to main pipe supplying heat-absorbers; o, valve for 

 controlling supply from tank A; B, section of piping passing 

 into cold brine; 6, valve controlling water direct from large 

 tank A; c, valve controlling amount of water from cooling 

 section B; C, thermometer at mixer; D, electric heater for 

 ingoing water; E, thermometer for ingoing water; d d d, 

 heat-absorbers inside calorimeter; F, thermometer indicating 

 temperature of outcoming water; G, can for collecting water 

 from calorimeter; f, valve for emptying G. 



