7- 



,. I;|1| . ,. 



.'FN-KTN AND MR. 1>. R. 



ON THE 



Serie* I. mea8urement8 were also made with the apparatus working in the normal 

 way described above, two thermo-junctions and a pressure gauge being connected as 

 sh^n in fig 3. In this series the principal quantities measured were the rate of 

 hW ,,f CO, and the electrical power supplied to the calorimeter to balance the 

 refrigeration. From these data the refrigeration, i.e., the heat absorbed per lb., 

 represented by the area NBECQ (fig. 2) was calculated. This is the heat required 

 to evaporate the liquid part of the CO, and to superheat it all from 6, to 8 , the heat 

 used in superheating being represented by the area PECQ. A series of experiments 

 was made with different values of 6 r A summary of the observations is given in 

 Table II. ; the results are also given in column a, Table VI. 



Experiments were not made at temperatures above 20 C. owing to the increasing 

 difficulties of manipulation. At the higher temperatures the weighing flask had to 

 he heated to keep the pressure above the evaporation pressure. At the same time its 

 capacity fell off rapidly owing to the great expansion of the liquid. The condenser 

 and pump had to be run at correspondingly higher temperatures and great care 

 exercised lest the condenser and flasks got over-full of the expanded liquid. 



CALORIHf TEH 1 CALOaiHf TEK 



Fig. 4. 



Series II. For this series the normal arrangement of the apparatus was slightly 

 modified, as shown in fig. 4. The liquid C0 2 , before reaching the throttle valve, was 

 led first through the second coil in calorimeter I., so that its temperature was reduced 

 to any required temperature & and then through calorimeter II., in which it was 

 warmed again at constant pressure to any desired temperature Q y . The quantities 

 measured were the rate of flow, the rise of temperature of the liquid, 6 y 6 z , and the 

 electric power supplied to calorimeter II. From these data the change of total 

 heat I of the liquid at constant pressure for the range 9 X to 6 y was calculated. Two 

 sets of experiments were made, one at 700 Ibs. per sq. in. pressure and one at 900 Ibs. 

 per sq. in. pressure. A summary of the observations is given in Table III. The 

 observations were plotted and smooth curves drawn through them. Figures taken 

 from the smooth curves are given in Table VII. This series of experiments does 

 not determine the absolute values of I, but only differences ; the zero of the I scale 

 was determined later, see p. 80. The slope of the I curve is the specific heat of the 

 liquid at constant pressure. Values of the specific heat deduced from the slope of 

 the curves are given in Table VII. 



