( 477 ) 
as to the question whether generally speaking the temperature of 
the vapour of any boiling liquid or of a solution is the same as that 
of the liquid. 
I may mention here that H. B. Hire!) and H. C. Jonus?*) have 
succeeded in constructing an apparatus, which gives very satisfactory 
results with certain solvents. Both have remembered, that in the 
first place care must be taken that the condensing liquid shall not 
come in direct contact with the thermometer. The method of Jones 
is much preferable to Hrre's method on account of its simplicity 
and also because it gives better results when using solvents of a 
high boiling point. When however I tried the process, using water 
as solvent, I found that the results were then not very accurate. 
Although in Jongs’ method, a displacement of the thermometer 
exercises little influence on the boiling point as the mercury reser- 
voir is entirely surrounded by metal, the boiling point is sensibly 
influenced by the method of heating. I further found that the method 
of S. L. BicELow ®) (heating by electricity) may give very good 
results in the case of non-electrolytes, if the platinum wire is not 
twisted into a spiral but left straight. If the wire is then passed 
through a small Utube the vapour bubbles do not come into contact 
with the mercury reservoir of the thermometer, but they ascend at 
both sides of the thermometer. Operating in this manner the boiling 
peint is constant when using the same number of ampères. This 
method is not at all applicable in the case of electrolytes on account 
of electrolysis setting in. An attempt which I made, to get a constant 
boiling point by heating with a boiling liquid instead of a flame, 
ended in failure. I used liquids of different boiling points. varying 
from 105° to 183° but did not obtain a constant boiling point in 
this manner. 
The result of my investigation is, therefore, as follows : 
The apparatus used till now for the determination of the increase 
in boiling point of aqueous solutions give very satisfactory results 
in the determination of molecularweights but they are not suffi- 
ciently delicate to study the decrease of vapour tensions. For this 
purpose metallic boiling vessels seem to be desirable, also an arran- 
gement which enables us to regulate with great accuracy the pressure 
above the boiling solutions and to keep the same constant. 
Amsterdam, Jan. 1900. Univ. Chem. Labor. 
1) Amer. Chem. J. 17, 502. 
*) Zeit. Phys. Chem. 21 114, 
3) Amer. Chem. J. 22 280. 
