296 Scientific Intelligence. 



This means that the critical temperature lies within the range just 

 given. The investigator observed liquid mercury at a tempera- 

 ture of 1500° C, so that the critical value 1270° C. published by 

 Koenigsberger is undoubtedly too low. 



The second plan involved the determination of the densities of 

 the liquid and vapor states. The experimental procedure con- 

 sisted in starting with small fillings (0*06 to 0*13) and noting the 

 temperature at the precise instant when the liquid phase vanished. 

 The value of the vapor density could be obtained at once from 

 the relative volumes of the filling and capillary. The density of 

 the liquid mercury at a chosen temperature could be calculated 

 by applying corrections for the amount of mercury vaporized to 

 the data found by the first method employed. When the points 

 are plotted in rectangular coordinates with densities and tempera- 

 tures as abscissas and ordinates, respectively, a smooth locus is 

 generated which has the general appearance of a parabola whose 

 axis makes an angle of about 100° with the positive direction of 

 the axis of density. The vapor density segment apparently 

 leaves the axis of ordinates at about 700° C. and curves away from 

 this line until, at the experimental limit 1400° C, the density is 

 approximately 1*6. The liquid density segment, on the other 

 hand, begins with the intercept 13*6 at 0° C. and bends toward 

 the temperature axis, the numerical value of the density being 

 about 7*8 at 1400° C. By dotting in the region of the vertex of 

 the curve the critical temperatiu - e is found to be roughly 

 1650° C. which confirms the result obtained from the first family 

 of curves. By assuming the validity of Boyle's law the author 

 of the original paper deduces the value 1 1 80 atmospheres for the 

 vapor pressure of mercury at 1400° C. 



In conclusion Bender calls attention to the following interesting 

 phenomenon which was observed between 1200° and 1300° C. At 

 1200° C. the vapor, which had appeared to be perfectly transpar- 

 ent and colorless at lower temperatures, began to show a faint 

 blue luminosity whose intensity increased as the temperature was 

 raised. For fillings less than 0*30 this could not be observed, 

 whereas it became sensible at 0*30 and above 0'40 at tempera- 

 tures of about 1300° C. and 1270° C. respectively. — Physik. Zeit- 

 schr. No 13/14, July, 1915, p. 246. h. s. u. 



6. The Thermal Conductivity of Neon. — According to the 

 kinetic theory of gases the specific thermal conductivity (k) is 

 connected with the coefficient of vicosity (77) and the specific heat 

 at constant volume (c v ) by the equation k = fyc v . For mona- 

 tomic gases/" should have the value 5/2, which agrees very well 

 with the experimental data 2*501 and 2-507 as obtained by 

 Schwarze for argon and helium respectively. For polyatomic 

 gases various theoretical expressions for /'have been deduced but 

 none agrees with the observed facts. To subject the matter to 

 further test Eeich Bannawitz has determined very carefully the 

 value of k for neon. Since Rankine found, for neon at 10*1° C, 

 7) = 3*036 X 10~ 4 and since c„ can be calculated from the theoret- 



