420 
of these ionic conductivities is 326. This ruimber may be derived 
in another way. H. E. Jones gives 380 as the limiting value for 
HF at 25°. The value as calculated above for 18° is 364. The 
difference per degree is 2.3 units, hence the value at 0° is 324. 
The approximate correctness of the number 325 is shown by the 
fact that if we assume the amount of dissociation to be little affected 
by temperature, at any rate in the more concentrated Solutions, we 
0 ° 18 ° 
get a = = -ü-f- . Substituting 0.0576 for a and 18.30 for 
^00 h GO 
p y wich is the value for the acid of 29.83 %, we get p^ =318 
(at 0°). 
“The temperature coëfficiënt for H at 18° is about 0.0153. If this 
is used to calculate the limiting value for the hydrogen ion at 0°, 
the number for p°° becomes very tnuch lower than any of these 
3 numbers given above, and as a coëfficiënt is only correct in the 
neighbourhood of 18° we discard this method of calculating.” 
It is evident that Hiel and Sircar have calculated p^ at 0° for 
H F assuming a very high value for H°. Their value for H° at 0° 
is about 100 units higher than the value obtained in this investi- 
gation in the direct way. Consequently all their calculations for 
the degree of dissociation of H F with this value for H° are not 
reliable. 
Chemical Laboratory, 
Presidency College, Calcutta. 
Chemistry. — " Proporties of dements and the periodic systein”. By 
Nilratan Dhar. 
(Aangeboden door de Heeren Ernst Cohen en F. M. Jaeger). 
In a former paper (Dhar Zeit. Elektro-Chem. (1913) it has been 
shown that the heats of ionisation of elements and the temperature 
coëfficiënt of mobility of ions are periodic functions of their atomic 
weights. In this paper it will be shown that some other properties 
are also periodic functions of their atomic weights. 
Surface tension, capillary rise etc. 
The surface tension of liquids being an important property has 
been investigated by various workers. There are several methods 
of determining the value of the surface tension of liquids, the most 
important ones are (1) the rise in a capillary tube, (2) measurements 
