(1947) 
influence of superheating by several methods viz. those proposed by 
BECKMANN, SMITS and von ZAWIDZKI, but none of them seemed to 
warrant greater accuracy. We refer to the fuller discussion which 
is to follow for the arguments to support this opinion. 
The choice of the substances was determined by theoretical consid- 
erations. The following rules follow immediately from the formulae 
given by VAN DER WAALS?) for the pressure-curves of mixtures 
for normal substances if the relation of GALITZINE-BERTHELOT 
ao = Ya, ag holds good, viz. that a minimum pressure cannot 
occur and that near the border a curve ascending from the border 
must be coneave seen from below. Now it is known of all 
substances which present a minimum of pressure, that they 
act chemically upon each other or are anormal in some other 
respect. Only the mixture ether-chloroform seems to be an exception. 
But as it is known that these substances may combine by the pre- 
sence of KOH and that they therefore may exercise some chemical 
attraction on each other, this contradiction is only apparent. Nor does 
the literature afford more than one exveption to the second rule, 
viz. the mixture of ether and chloroform examined by GUTHRIE, 
and for these substances we have most likely not to think of chemical 
action or anormality. from other causes. But the experiments of 
Gururie do not seem to be very accurate and his curve shows 
clearly that it was his aim to find so called molecular combinations. 
On account of the great importance of the matter, for the question 
is here whether the conduct of a mixture of two substances may 
be represented only from quantities, characteristic for each of these 
substances separately, or whether another quantity will appear 
indicating a mutual influence, it seemed advisable to us, to subject 
the mixture to a new investigation. We give our results in the 
table, where w is the molecular proportion of ether, and p the pres= 
sure. The temperature is 33°25. (See table p. 158). 
These values show clearly that the combination of the two liquids 
chloroform and ether is not only contrary to the second of the 
rules given above, as might be expected from the course according 
to GUTHRIE, but also to the first. For it is evident that this curve 
shows a minimum, though it is quite on the border. So this curve 
is remarkable also in this respect, that it adds a second case where 
dp Bea 
El = 0 to the one found already by CUNAEUS; a possibility 
day} 0 
which was doubted from different sides. 
1) Proceedings Vol. ILL p. 163. 
