( 668 3 
With this value for x I have calculated according to formula (7) 
the corrections to be applied to p, in order to arrive at the saturated 
vapour pressure of the pure substance. The values of p found thus 
are given in column p of the table. They agree well with the pres- 
sures given by KUENEN !) for almost pure ethane. Further according 
to formulae (2a) and (2b) of communication n° 75: 
Belt re) 
oes 2, é 
dr (5-42) 
where I have put ee = 6.86 and for C4 ad Te 
found there for carbon dioxide, I have calculated the corrections to 
be applied to the plaitpoint temperature and pressure observed in 
order to obtain the critical temperature and pressure of pure ethane. 
So I found: 
) the value —32.2 
ty 32:0° C. ‘and pp — 48:2 atin, 
which values according to those given by KUENEN for almost pure 
ethane, cannot differ much from the real values. 
One would now be induced to calculate from the increases of 
vapour pressure for almost pure ethane given by KUurNeN Le. the 
composition and then the corrected values for the pure substance. 
As beforehand nothing is known with certainty about the character 
of admixture, one might wish to calculate « and /? from the obser- 
vations on the increase of pressure at different temperatures, but it 
then appears that the temperature range of the observations is too 
small to allow us to calculate « and /? separately. If however the 
observations do not allow us to make this calculation, it appears 
sufficiently from the preceding that the formulae communicated are 
confirmed by KuENeEN’s observations, and that they may have a 
practical value in the reduction of similar series of observations with 
a not altogether pure substance. | 
1) Comp. Kuxnen, Zeitschrift für comprimirte und flüssige Gase, I, p. 159, table 5, 
