35 6 



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



DESCRIPTION OF THE EXPERIMENTS. 



Measurement of the Total Heat of CO 2 Gas. 



The method employed in these experiments was the same as that used in the former 

 series (Series III., p. 73), but the apparatus was modified in several details. The gas 

 used was, as before, supplied by Messrs. Barrett and Elers, Limited ; the same instru- 

 ments were used for weighing the gas, measuring its pressure and temperature, and 

 the electric heat given to it. The instruments were re-calibrated from time to time as 

 a check, in the same manner as before. 



The weighing flasks, condenser and drying flasks were the same as before, but 

 calcium chloride was used in the drying flask instead of phosphorus pentoxide, which 

 occasionally gave trouble. The single-stage pump was replaced by a larger two-stage 

 pump lent for the purpose by Messrs. J. and E. Hall, of Dartford. With this pump 

 the rate of working could be more easily controlled, and the attainment of low 

 pressures was facilitated. The large calorimeter (No. I.) was discarded, and the 

 evaporation and warming of the gas was done in calorimeter No. II. with the addition 

 of a simple heating vessel made of a length of 2^-inch steel pipe enclosing an electric 

 heating resistance. 



SCALE 



INCHES 



Fig. 1. 



All measurements of heat were made in a new 1-inch tubular calorimeter, fig. 1. 

 This calorimeter consists of a central body with a thermojuriction fitting at each end. 

 The central body is made up of three concentric pipes held between two vulcanite 

 ends ; the outer pipe is made of steel, the intermediate pipe of vulcanite, and the inner 

 pipe of fused silica. Inside the inner pipe is a coil of nickel-chrome wire forming the 

 heating resistance. Folded round the outside of the silica tube is a thin strip of 

 copper which serves as the return lead for the current flowing through the heating 

 coil. The whole is held together by two external bolts. The gas enters at one end, 

 passes through the silica tube, and then returns outside the silica tube and inside the 

 vulcanite one, and finally returns again outside the vulcanite and inside the steel tube. 

 At each end are the two thermojunction fittings ; they are the same fittings as were 

 used with the throttle valve. 



