94 |.,J,,F. f. FKKtt'EN JENKIN AND MR. D. R. PYE ON THE 



\Vl.rn making an .-xprriment, the bath was first cooled to the desired temperature. 

 Thru rra.lings were taken with the cathetometer as the pressure was varied step by 

 >t, ). IP.III tlir iiiaxinniin available to a pressure just above the saturation pressure 

 corresponding to the temperature of the bath. These readings give a constaut- 

 temperature curve on the p.v. diagram. A series of experiments was made with 

 different temperatures, so that a number of constant-temperature curves were 

 obtained, as shown in fig. 11, p. 78. 



The apparatus appeared to work satisfactorily, but the results obtained are not in 

 perfect agreement amongst themselves ; the cause of this has not yet been ascertained. 

 The curves shown in fig. 1 1 have been arbitrarily constructed to represent the mean 

 results of several sets of observations and to agree amongst themselves ; they must be 

 taken as only approximate, but they are sufficiently accurate to determine the small 

 correction 3, Table VI., for which they are required. AMAGAT'S (5) curves have been 

 added to fig. 1 1 for comparison. 



By extrapolation the curves may be extended to the left to the saturation pressure, 

 which is only just below the lowest pressure observed. This has been done in fig. 11. 

 By joining up the ends of all the curves, the new curve (named "limit curve" in the 

 figure) is obtained which shows the change of volume along the limit curve. A curve 

 giving BEHN's(6) observations is also drawn for comparison. The agreement is fairly 

 good. 



It is not necessary to describe the lengthy and rather complex calculations required 

 to reduce the data obtained in these experiments. Allowance was made for the 

 changes of volume of the glass and of the mercury indicator at different temperatures, 

 and corrections applied to allow for the variation in the bore of the tube. All these 

 corrections are small compared with the changes of volume of the C0 2 due to 

 temperature. Since the actual weight of the column of liquid CO 3 was not measured, 

 the density at some one temperature had to be assumed ; BEHN'S value, viz., 0'925 

 at C., was used. 



The elasticity and dilatation may be derived from the curves directly. The 

 elasticity (dv/dp) t is the slope of the constant temperature lines. The dilatation 

 (dv/dt), is the distance apart of the constant temperature lines divided by the 

 difference of temperature. 



These quantities have not been worked out because of the known inaccuracy of the 

 observations. The authors intend to repeat the experiments and hope to obtain 

 accurate results. 



PART IV. DISCUSSION OF RESULTS. 

 Pressure-Temperature Cuwe. (Fig. 18. Tables I. and X.) 



Tl, n-lation between the pressure and temperature of saturated CO 2 vapour has 

 by RKUNAULT (7), CAILLSTET ( 8 ), AMAGAT (5), KUENEN and KOBSON (9), 



