( 478 ) 
at the same temperature and pressure, we obtain points which 
all lie in one curve, this curve therefore represents the variation of 
the density in the tube; from the shape of this curve, which very 
much resembles that of an isothermal in the neighbourhood of the 
critical point, it is evident that the substance in the tube cannot but 
show considerable differences of density. 
I assume that between the two ends of the tube there is a ceftain 
difference in composition; then the greatest difference in density 
depends not only on the @ and the 6 of the substances considered, 
and on the difference in composition, but also on the temperature, on 
the mean density and on the mean composition. For those mixtures 
of which the « and the @ are known, I now shall give the difference 
in density which corresponds to za, = 0.001, if the temperature 
is about the critical temperature of the pure substance and the mean 
density is also the critical density : 
CO, with 0.001 mol. CHsCl ,#= 0.878 , B= 0.088 , n=34"/, of the 
CHC,» » CO ,2=—0221,@=- 0281 AS 
CO. vene He Stam Bh 1669 ae 
6 a ER 6 ag y_ \density. 
GO NRO a= 066~ B 1.09) = BONA 
The following differences in density would be observed in carbon 
dioxide with small quantities of oxygen, with different temperatures 
and differences of concentration, the mean density being still the 
eritical one : 
i a 2, = 01008 c.— 2, ON aa (OO 
d 2 2 
31°.0 A =36°/, A = 30°/, A =17/, 
31°.5 24 17 6 
32° 17 10 2.5 
33° 12 5 + 1/, 
34° 6 3 =e 
How the difference in density depends on the mean density of 
the substance may be seen from the following table, which relate to 
carbon dioxide with oxygen at a temperature of about 31° C. and 
for #,—v, — 0.001. 
Mean density 1.39, [AS 
1.2 8 
: Areal 24 
1.0 36 
0.9 24 
0.8 6 
0.707 1.5°/, 
salts in liquid sulphur dioxide. These experiments, therefore, where an admixture 
had intentionally been added, have been erroneously adduced as arguments against 
the theory of Axprews and van per Waars; for the rest Hagensacu himself has 
understood the cause of the deviation he had found. 
