( 635 ) 
Chemistry. — “Determinations of the diminution of vapourpres- 
sure and of the elevation of the boiling point of dilute 
solutions”, by Dr. A. Smrrs (Communicated by Prof. H. W. 
Bakuuis RoozeBoom). 
Introduction. 
In a former article ') the apparatus has been described, which has 
enabled me to ascertain the decrease of the vapourpressure and 
the elevation of the boiling point of dilute solutions. 
The method of experimenting when determining the diminution of 
vapourpressure is already described there, so that it is only neces- 
sary to say here that in determining the elevation of the boiling 
point, the manostat is always set at the same pressure; the thermo- 
meter, which remains continuously in the boiling water, controls 
the action of the manostat, since a small change of pressure in the 
apparatus is immediately betrayed by a change of temperature. 
Regarding the accuracy of the two methods, the preference must 
be given to the determination of the increase in the boiling point. 
If, in the method for determining the diminution of vapourpressure, 
the decrease in the vapourpressure of the solution is to be caleu- 
lated from the observed fall in the boiling point of pure water, it 
is necessary to use the table constructed by Ruanautr?) for the 
maximum pressure of watervapour, which gives the differences for 
each 0.1°. It is plain that errors are committed here; in the first 
place because the table is not quite correct and secondly because 
interpolation must be resorted to. The value of # obtained from the 
value of the decrease in the vapourpressure thus calculated can, 
therefore, not be very accurate. In the determination of 7 from the 
elevation of the boiling point, it is only necessary to divide by a 
constant factor; in this method the values of # can only be affected 
by a constant error. 
J have, therefore, applied the two methods to the same solutions 
of NaCl, but in the case of the other salts, the elevation of the 
boiling points only has been determined. The results, which I have 
obtained with solutions of NaCl, KCl and K NOs are included in 
the following tables. Between each of the different series of obser- 
vations of the NaCl-solutions, the manostat was set at a different 
pressure. 
') Proceeding Royal Acad. Jan, 27, 1900, p. 471. 
2) Mémoires de Acad. T. XXI, p. 632. 
