268 
2. It appeared, however, more and more that the critical tem- 
perature of mercury lies much higher than 900° or 1000° C. 
Traupe and Tricaner found no critical phenomena at 1000° ©.. 
and Happen ') calculated 7’, = 1370° abs. (= 1097° C.), p. = 456 atm, 
from different observations. This would, therefore, be only 100° 
higher than my first estimation. W. C. Menzies *) came to 1275° C. 
(675 atm.), while it became clear from KÖNIGsBERGER’s experiments *) 
that the long sought critical temperature must lie above 1400° C. 
(1000 atm.). At + 1200° U. the meniscus becomes flat; only the 
liquid is luminous. Below 1400° C. there are seen small glowing 
drops, which rise from the liquid and fall back into it, or dissolve 
in the not-luminous vapour. At 1400° C. the emission of light of 
the liquid rapidly ‘diminishes, and the critical temperature seems to 
be near. 
Then followed Miss J. Bunper’s experiments“) giving determinations 
of density of liquid and vapour up to 1400° C. At 1400° C. the 
vapour was still quite transparent; “the distance of the mercury 
atoms, therefore, is still so great that the electron cannot yet detach 
itself from the atom, and can, therefore, not yet take charge of the 
conduction of the electricity.” At 1500° C. (one observation) ° 
there was still liquid mercury present. 
When the observed densities are represented in a 7'v-diagram, 
we arrive through graphical interpolation at 7, = 1400° C. about, 
or slightly higher, hence about 1700° abs. (1427° C.), whilst p, must 
be at the least 1100 atm. For the critical density about 4,15 is found. 
(GuLDBERG calculated 3,8). 
3. It is the question if this high critical temperature of + 1700° 
abs. can be theoretically justified. For this purpose it is required, 
as we shall see, to modify the values of 6, and Wa, for 1 Gr. atom 
of mercury somewhat. Instead of 10°6,=150 the lower value of 
about 120 must be assumed for it, while instead of 107” a.— 11 
it is necessary to assume 10 (hence 10*a,= 100 instead of 121). 
That at such a high temperature as 1700° abs. the values of a 
1) Ann. der Ph. (4) 13 (1904), p. 340 and 620. 
2) Am. Chem. Soc. 35 (1913), p. 1065. 
3) Chem. Zg. 36 (1912), p. 1321. Cf. also RorinJANz and SucHopskI, Ann. Inst. 
Pol. P. le Grand 23 (1915), p. 668. 
4) Physik. Zeitschr. 16 (1915), p. 246; 19 (1918), p. 410. 
6) Neither KÖNIGSBERGER, nor Miss BENDER state clearly in what way their 
observations of the temperature have been made. This remains in my opinion the 
weak point. 
