be in a position shortly to furnish further information on this point, and also, if possible, to say whether the fall in dielectric constant is accompanied by a reduction in the refractive index; that is to say, whether Maxwell’s law is obeyed at low temperatures.
We may add that we have already devised a method by which it will be possible to construct a condenser without the above-described distance pieces, and hence to free the resulting measurement from the small uncertainty—amounting, perhaps, to about 1 per cent, which may affect the above-given numerical results, and which comes in in consequence of the doubt existing as to the exact area of the separators, and also the exact dielectric constant of the glass at the low
It is interesting to observe that the numbers which we have found above for the dielectric constant of liquid oxygen and liquid air are not very different in order, though somewhat smaller than the dielectric constant as already determined for some other liquid gases,* such as nitrous oxide and carbon dioxide.
In conclusion, we may add that we have been again much indebted to Mr. J. E. Petavel for his kind assistance in making the abovedescribed observations and measurements.
Note added December 15.
In connection with the above investigation, it is interesting to note one remarkable difference between the magnetic susceptibility of oxygen in the liquid and in the gaseous state. The mass of 1 c.c. of gaseous oxygen, taken at 15° C. and 760 mm., is 0*00134 gramme. The mass of 1 c.c. of liquid oxygen, taken at —182° C. and 760 mm., as determined by one of ns (J. Dewar), is 1*1375 gramme. Hence the ratio of the density of liquid oxygen to that of gaseous oxygen is 849 to 1. ^
The magnetic susceptibility of gaseous oxygen at 15°C. and /60 mm., as obtained from the figures given by Faraday and E. Becquerel, is 0143 X 10~6 per unit of volume, whilst the magnetic susceptibility in the liquid state is, as we have shown,t 228 X 10~6. Hence the ratio of the magnetic susceptibility of liquid oxygen to that of gaseous oxygen for equal volumes is 1594 to 1.
In other words, the magnetic susceptibility of liquid oxygen is nearly twice as great as that of gaseous oxygen for equal masses, dhe inference is that magnetic susceptibility is not merely a property of the molecule perse, but is a function of the state of aggregation.
- See F. Linde, ‘ Journal de Physique,’ vol. 5, Sept., 1896, p. 413, “ On the
Dielectric Constant of Liquid Gases.”
t See Fleming and Dewar, 4 Roy. Soc. Proc.,* yoI. 60, p. 283, December, 1896.
