THERMAL PROPERTIES OF CARBONIC ACID AT LOW TEMPERATURES. 87 



the bath a few degrees above 6 a , so as to make sure that the gas leaving the calori- 

 meter was slightly superheated. This was checked by the direct measurement of the 

 final gas temperature ft, by a thermo-junction in the pipe. 

 During the test the following observations were made : 

 Times when the weighing l>ell rang ; 

 K.M.F. on each heating coil, observed every minute ; 

 Pressure of gas leaving coil, ; 



Temperature fy of liquid OCX, before the throttle valve, every three minutes ; 

 of gas 6 3 leaving calorimeter, every three minutes ; 



,, bath, every three minutes ; 



,, cold junction, several times during test ; 



atmosphere, . 



During the test small adjustments of the throttle valve and of the electric power 

 were made so as to keep the pressure and bath temperature as constant as possible. 

 As an example, the complete records for one experiment are given in Tables XI. 

 and XII. The times when the weighing bell rang were plotted as a check on the 

 uniformity of the rate of flow of CO., during the experiment. The initial temperatures 

 of the liquid CO a were plotted to obtain the true mean. 



In Series II. the apparatus was connected as shown in tig. 4, p. 72, the object being to 

 measure the total heat I of the liquid, i.e., the heat represented by the area SKAM, 

 fig. 7, p. 74, for a series of ranges of temperature. The speed of the pump was settled 

 as in Series I. The electrical power entering the large calorimeter was adjusted so as 

 to keep its temperature a few degrees below 6 t , so that the liquid C0 2 might be cooled 

 to the desired temperature 6 4 . The electrical power put into the small calorimeter 

 was adjusted so as to keep it at the selected temperature 0,. The throttle valve was 

 adjusted so as to keep the evaporation temperature a little below the temperature of 

 the large calorimeter, but this temperature was of no importance in this series. 



During the test the following observations were made : 



Times when the weighing bell rang ; 



E.M.F. on each heating coil in calorimeter II., observed every minute ; 



Temperature 6 t of liquid CO a entering calorimeter II., every three minutes ; 



>, Qi leaving ; 



of bath, calorimeter II., observed every three minutes ; 



,, cold junction, several times during test ; 



atmosphere, 



No observations were entered for the large calorimeter, which was only used as a 

 cooler for the liquid, but the power was adjusted as required to keep its temperature 

 constant. 



As an example, the complete records for one experiment are given in Tables XIII. 

 and XIV. 



