THE CALORIMETER- 23 



cooler B, and by adjusting the valve 6 and valve c any desired mixture of 

 water can be obtained. A thermometer C gives a rough idea of the tem- 

 perature of the water, so as to aid in securing the proper mixture. The 

 water then passes under the floor of the calorimeter laboratory and ascends 

 to the apparatus D, which is used for heating it to the desired temperature 

 before entering the calorimeter. The temperature of the water as it enters 

 the calorimeter is measured on an accurately calibrated thermometer E, 

 and it then passes through the absorber system d d d and leaves the calo- 

 rimeter, passing the thermometer F, upon which the final temperature is 

 read. It then passes through a pipe and falls into a large can G, placed 

 upon scales. When this can is filled the water is deflected for a few minutes 

 to another can and by opening valve / the water is conducted to the drain 

 after having been weighed. 



Brine-tank. — The cooling system for the water-supply consists of a tank 

 in which there is immersed an iron coil connected by two valves to the 

 supply and return of the brine mains from the central power-house. These 

 valves are situated just ahead of the valves controlling the cooling device in 

 the refrigeration room and permit the passage of brine through the coil 

 without filling the large coils for the cooling of the air in the calorimeter 

 laboratory. As the brine passes through this coil, which is not shown in 

 the figure, it cools the water in which it is immersed and the water in turn 

 cools the coil through which the water-supply to the calorimeter passes. 

 The brass coil only is shown in the figure. The system is very efficient and 

 we have no difficulty in cooling the water as low as 2° C. As a matter of fact 

 our chief difficulty is in regulating the supply of brine so as not to freeze 

 the water-supply. 



Water-mixer. — If the valve 6 is opened, water flows through this short 

 length of pipe much more rapidly than through the long coil, owing to the 

 greater resistance of the cooling coil. In conducting these experiments the 

 valve c is opened wide and by varying the amount to which the valve & is 

 opened, the water is evenly and readily mixed. The thermometer C is in 

 practice immersed in the water-mixer constructed somewhat after the prin- 

 ciple of the mixer inside the chamber described on page 21. All the piping, 

 including that under the floor, and the reheater D, are covered with hair-felt 

 and well insulated. 



Rate-valves. — It has been found extremely difficult to secure any form of 

 valve which, even with a constant pressure of water, will give a constant 

 rate of flow. In this type of calorimeter it is highly desirable that the rate 

 of flow be as nearly constant as possible hour after hour, as this constant 

 rate of flow aids materially in maintaining the calorimeter at an even 

 temperature. Obviously, fluctuations in the rate of flow will produce fluc- 

 tuations in the temperature of the ingoing water and in the amount of 



