( 244 ) 
that for this system the points G and H nearly coincide^ or in other 
words that in fig. 6 the line AB passes about through the double point. 
Butane and methyl alcohol then at once begin with a rise of tem¬ 
perature with increasing pressure, though it is very small (-j-0.007) 
at first, and the successive homologues begin then with always higher 
positive value of —: Isopentane with -f 0.02, hexane with 0,03, 
d P 
decane with 0.04. 
In connection with this the question rises if really the first system 
of this series, methyl alcohol with ethane investigated by Kuenen, 
is simply a case of 3; or if it should be considered as an example 
of type 5, which is analogous to 2, a question which we shall not 
try to decide for want of data. 
We have not been able to reach the point E in any of our binary 
systems 1 ), here too, probably on account of the rapid increase of 
the pressure. Some of the systems of water with bases of the 
pyridine-series are examples of this type, which present a perfectly 
closed plait, for which therefore in any case such a point must 
occur, and these plaits being of small extension, we may expect to 
succeed in reaching the point E. We hope shortly to be able to 
take this investigation in hand. 
We may remark in conclusion that in all the cases, in which the 
vapour-pressure line of the system has been determined, the rule 
derived by van der Waals, appears to hold: Splitting up of a plait 
takes place only when there is a maximum in the vapqur-pressure 
line (min. critical temperature of the unsplit mixture). 
Amsterdam. Physical Laboratory of the University. 
Chemistry. — “On the system water-natrium mlphate”. By Prof. 
A. Smits and Dr. J. P. Wuite. (Communicated by Prof. A. F. 
Holleman). 
Already before 2 ) one of us succeeded in showing that the system 
water-natrium sulphate belongs to the type ether-anthraquinone, in 
which the probability was also pointed out that this would also be 
the case for the other systems water-salt which show a retrogressive 
solubility curve. 
As the above behaviour was found in a preliminary investigation, 
b We have reached it, however, in the ternary system : Pyridine + water + 
natrium carbonate. 
-) Smits. Inaugural address. Amsterdam, Dec, 9, 1907, p. 19, 
