581 
to the adopted masses also cannot help us. If the mass of Mercury 
were multiplied by 8, which of course in itself is outside all limits 
of probability, the node of Venus would be put right, but we should 
then have a still larger discrepancy e.g. in the perihelion of Venus. 
It is not possible to find a system of masses which will reduce all 
residuals to within their mean errors. 
Chemistry. — “Investigations on the Temperature-Coefficient of the 
Free Molecular Surface-Energy of Liquids between — 80° 
and 1650° CC”: XV. “The Determination of the Specific 
Gravity of molten Salts, and of the Temperature-Coefficient of 
their Molecular Surface- Energy’. By Prof. Dr. F. M. Jarcrr 
and Dr. Jur. Kann. 
(Communicated in the meeting of June 24, 1916). 
$ 1. For the calculation of the molecular free surface-energy of 
the molten salts and other compounds, about which we have pre- 
viously communicated '), it is necessary to know the specifie gravity 
of the investigated liquids at temperatures ranging from — 80° up 
to 1650° C. 
As far as organic liquids are concerned, the usual and generally 
known methods can be applied, — at least if the temperatures of 
measurement are not too far apart from the range usually considered 
in laboratory-experiments. In those cases we used in the first place 
the pycnometer. Commonly this consisted in a double-walled vessel, 
the space between the glass-walls being carefully evacuated; it was 
closed by means of a ground thermometer. In most cases the densities 
were determined in thermostats at 25°,50° and 75°C. In the work 
with liquids of low boilingpoint such measurements had to be made 
also at the temperature of melting ice, or in refrigerant mixtures 
of salt and ice, or in those of solid carbondioxide and alcool; in 
these cases the pycnometer is evidently not a suitable instrument, 
and the pyenometrical method appears for many reasons, much less 
adapted than the volwmetrical method. 
More particularly in the determination of the specific gravities of 
the low-boiling aliphatic amnes, which moreover will absorb readily 
the carbondioxide and the water-vapour from the atmosphere, the 
volumeter appeared to be the only applicable instrument, while 
ecliptic. For the planetary precession we should have a correction amounting to 
+0,”30 per century. These residuals are not appreciably better than those given 
above in the text. (Note added in the English translation). 
1) F.M JAEGER and Collaborators, these Proceedings, 1914, 15 and 716. 
