358 



PROF. C. FEEWEN JENKIN AND MR. D. R. PYE ON THE 



The general arrangement of the apparatus is shown in fig. 3. The liquid CO 2 from 

 the weighing flask expands through the throttle valve V, and is evaporated in the 

 2^-inch heater. From there it passes in the condition of nearly dry vapour into 

 No. II. calorimeter where the evaporation is completed and the gas is warmed to the 

 desired temperature. It then passes into the 1-inch calorimeter where its temperature 

 is raised through an accurately measured range by the application of an accurately 

 measured electric power. From this calorimeter it passes on through, regulating 

 valves and a drying flask to the pump, which compresses it into the condenser and so 

 back to the weighing flasks. 



The object of the 2^-inch heater was to facilitate the regulation of the temperature 

 of the gas. By adding most of the heat necessary for evaporation in the 2^-- inch 



STXI/WVWO 

 GAG (7) 



V 6 Y* 



DRYING 



FLASK 



OIFF- 



GUAGE CMJORIMETEfl 



Fig. 3. 



(-24 



heater, the temperature of calorimeter No. II. could be kept only a few degrees above 

 the required gas temperature, so it acted as a steadying reservoir of heat. Without 

 the 2^-inch heater the arrangement was unstable, for then the calorimeter No. II. had 

 to be kept much warmer in order to transfer sufficient heat to the vapour. The 

 point where the vapour became dry was then near the top of the coil, and the least 

 variation in the rate of flow made this point move up or down and so left a varying 

 amount of surface for superheating the gas, the temperature of which, therefore, 

 varied widely. For experiments at low pressures, viz., 150, 200, 300 and 400 Ibs. 

 per square inch, the speed of flow was controlled by the valve Vj while V 2 and V 3 

 were open. For the experiment at 500 Ib. V 3 was also partially closed. For the 

 experiments at 600 and 700 Ib. V 3 was open and V 2 was partially closed. For the 

 700-lb. experiment the weighing flask had to be slightly warmed by a gas ring. 

 During an experiment the valve V 5 was kept open and V 6 closed, so that the standard 



