Vapour-pressure and the Volumes of Vapour and Liquid. 139 



and for E the previously determined value, we get 



7=0-0017352. 



JSTow, when with the help of the value of TV C and w c repre- 

 sented by 2y the quantities "W and w have been obtained from 

 the above-mentioned fractions ~W/W C and w/w c and we wish 

 from those quantities to arrive at the volumes s and a of the 

 ether vapour and liquid, we must for that purpose know the 

 constant a. also, since s = Vf + a, and <r=iv + a. For the de- 

 termination of « it is best to employ any observed volume of 

 the liquid, from which the calculated value of w for the same 

 temperature is to be subtracted. At 0°, according to Kopp, 

 liquid ether has the specific gravity - 73658, from which, con- 

 sidering that the volume <t refers not to the pressure of 1 atin., 

 but to that of 0-2426 aim., we get o- = 0-0013578. In like 

 manner we get for 20°, according to Kopp, <r=0'0014001. 

 If with the help of these quantities we determine a. and take 

 the mean of two closely accordant values, we find 



« = 0'0010876. 



It may here at once be added, further, that after the deter- 

 mination of 7 and a. the value of /3 also immediately results, 

 since /3 = 7— a. There comes, namely, 



£ = 0-0006476. 



Employing the found values of the constants, we can now 

 calculate from the fractions W/W c and w/w e the quantities s 

 and <x, and obtain for the above-considered series of tempera- 

 tures the following values: — 



t 



-20° 



0° 



20° 



40° 



60° 



80° 



s ... 

 (7 ... 



3182 

 0001318 



1-238 

 0-001356 



0-5562 

 0-001402 



0-2793 

 0001455 



0-1524 

 0001520 



008883 

 0-001600 



t 



100° 



120° 



140° 



160° 



180° 



190° 



S ... 

 ff ... 



005417 

 0-001702 



003408 

 0001837 



002175 

 0-002030 



001373 

 0-002335 



0003016 

 002982 



0004558 

 0004553 



In conclusion, the form which the general equation (3) 

 assumes after the determination of may now be added. 

 According to (7) and (4) we must put 



e, 



(«t- 



•*)=^(«T-*. 



■b). 



