Constant of Ice and Alcohol at very Low Temperatures, 5 



M. E. Bouty ('Journal de Physique,' 3 S., vol. 1, 1892, p. 454) 

 found by a slow-speed method a value of 78*8 for the specific induc- 

 tive capacity of ice at —23° C. and upwards, whilst R. Blondlot 

 (' Compt. Rend.,' vol. 119, 1894, pp. 595 — 597), using electric waves 

 and measuring the wave-lengths in air and in ice, found 1*41 for the 

 electric refractive index of ice, and hence the number 2'0 as the 

 value of the dielectric constant of ice at a temperature not stated, 

 but presumably not far below 0° C. 



Also A. Perrott (' Compt. Rend.,' vol. 119, 1894, p. 601, also 

 ' Compt. Rend.,' vol. 114, June, 1892, p. 1528) found the value 143 

 for the refractive index, and hence 2'04 for the square of the elec- 

 tric and refractive index of ice. C. B. Thwing, working with electric 

 resonance, and therefore very rapid reversals, gives (' Zeits. Phys. 

 Chem.,' vol. 14, 1894, pp. 286—300) 3-36 at -2° and 2'85 at -5° C. as 

 values for the dielectric constant of ice. 



It seemed desirable to endeavour to throw light on the reasons for 

 these differences by an examination of the dielectric constant of ice 

 at very low temperatures.* We have accordingly applied the method 

 and apparatus used by us in the latest determinations of the di- 

 electric constant of liquid oxygenf for the purpose of making an 

 examination of the dielectric constant of ice and frozen ethyl alcohol. 



A condenser was constructed consisting of three very thin con- 

 centric brass tubes about 20 cm. in length. The extreme outer and 

 inner tubes, having diameters of 3*74 and 3 cm.' respectively, were 

 connected together metallically at the bottom, and formed one plate 

 of the condenser. An intermediate brass cylinder 337 cm. in dia- 

 meter was suspended between the inner and outer tubes, thus forming 

 the other plate of the condenser. This last plate was insulated and 

 suspended from the others by providing it with small wire attach- 

 ments, which were passed through the holes in six glass beads 

 wedged in between the inner and outer connected cylinders at the 

 top and bottom as shown in fig. 1. This condenser was contained in 

 another brass cylinder closed at the bottom, and then had its dielec- 

 tric formed of ice by filling the annular space between the cylinders 

 with distilled water and freezing it. The terminal wires from this 

 condenser were connected to a rapid contact maker driven by an 



* Note added February 15, 1897. Since this Paper was presented a communica- 

 tion has been made to the Royal Society by Dr. J. Hopkinson and Mr. E. Wilson, 

 in which they describe experiments on the dielectric constant of ice. These authors 

 find that the specific inductive capacity of ice, when measured with electro- 

 motive force reversals having a period of from 1/100 to 1/10 of a second, is a 

 mimber of the order of 80, but if measured with periods such as 1/10 6 of a second 

 it is a number less than 3. The difference they ascribe to residual charge. Hence 

 it is clear that these observations are in accord with those of Bouty and Blondlot. 



f Fleming and Dewar, " On the Dielectric Constant of Liquid Oxygen," ' Boy. 

 Soc. Proc.,' 1896, vol. 60, p. 358. See note added December 18, 1896, p. 368. 



