82 PROF. C. FREWEN JENKIN AND MR. P. R- PYE ON THE 



fig. 6, p. 73. They agree closely with MOLLIEE'S curves, as may be seen in fig. 13 (p. 81), 

 where a few of each (at different pressures) are drawn for comparison. 



Tim four dryness curves on the diagram were drawn by dividing the distances 

 between the limit curves into quarters. This completes the construction of the 

 diagram. 



PART II. DETAILED DESCRIPTION OF THE APPARATUS AND METHOD OF CARRYING 

 our THE EXPERIMENTS SERIES I., II., AND III. 



The compressor is a single acting pump made by Messrs. J. and E. Hall, of 

 Dartford. It is driven by a variable speed electric motor. The piston-rod gland is 

 formed of a pair of cup-leathers, between which oil is forced by an auxiliary piston, 

 thus no leakage of CO., takes place, but a little oil enters the cylinder, and is pumped 

 over with the CO 3 ; it is mostly caught in an oil separator, but a trace of oil is carried 

 round the whole circuit with the CO-j. Under ordinary conditions the pump runs 

 cold, but when working under the abnormal conditions of some of the tests it ran hot 

 and gave trouble till a water-jacket was fitted round the cylinder. 



The condenser is a coil of pipe in a tank through which cooling water flows. 

 The drying flask is a steel flask containing a little phosphorus pentoxide. The gas 

 is led in by a pipe leading nearly to the bottom of the flask and leaves by a pipe from 

 the top. A few ounces of P a O 5 were put in the bottom of the flask and renewed from 

 time to time. When the apparatus was first tried great trouble was experienced 

 with moisture which collected and plugged the throttle valve with ice. The whole 

 apparatus had to be thoroughly dried out and all the gas dried by passing it through 

 calcium chloride in the drying flask before the difficulty was got over. After this all 

 fresh charges of gas were passed through a small flask filled with calcium chloride 

 before they entered the apparatus, and the above described drying flask was kept in 

 circuit to eliminate any traces there might be left. Some of the oil carried round by 

 the CO;, collected in this flask. 



The u-etghing apparatus (see fig. 1, p. 70) consists of two steel flasks, each capable of 

 holding -in 11 is. of liquid CO.,; both were originally hung on spring balances. Each 

 flask has valves at the top and bottom so that they may be alternately filled and 

 emptied. The connections to the flasks are made of coils of copper pipe, flexible 

 enough to allow of a small vertical motion. The spring balances were calibrated to 

 allow for the stiffness of these coils. This arrangement had certain defects and was 

 subsequently modified. In order to be sure that no CO 2 passed unweighed, it was 

 necessary to stop the supply of C0 a from one flask before starting it from the other ; 

 this inevitably caused a momentary variation in the rate of flow. There was also 

 some doubt as to the effect of the weight of C0 8 in the coils of pipe connected to the 

 flasks, which might be full or empty at the moment of weighing. The spring- 

 balances were divided in pounds, and tenths of a pound could be roughly estimated. 



