Constants of Metallic Oxides at Lota Temperatures. 377 



Dielectric Constant of Ice, having in suspension a small quantity of finely 



divided Sidphur. 



Corrected galvanometer deflection when the condenser has air as 

 dielectric = 413 cm. for 100 volts. 



Mean 



Temperature galvanometer 



in platinum deflection Dielectric 



degrees. in centimetres, constant. Observations. 



— 198-2 11 1 2'64 Condenser charged to 98-2 volts. 

 -1825 11-3 2-69 



— 160-0 4*2 5*44 Condenser charged to 1'43 volts. 



The resnlts show that practically no influence is produced upon the 

 ■dielectric quality of the ice at very low temperatures when it is 

 impregnated either with conducting particles of gold or non-conduct- 

 ing particles of sulphur. The amount of gold in the ice as used by 

 us is no doubt small. In each case the dielectric constant of the 

 material is very close to that of the ice obtained from pure distilled 

 water. 



The electrical resistance of the ice slightly impregnated with finely 

 divided gold did not appear to be less than that of ordinary ice. 

 To the tests we applied the one appeared to be as good an insulator 

 as the other. 



The foregoing observations are graphically delineated in the 

 diagrams in figs. 1, 2, and 3, according to the magnitude of the 

 dielectric constants found. The following facts may then be noted : — 



(i) The presence of caesium hydrate, lithium hydrate, bismuth 



oxide, aluminic oxide, finely divided sulphur or finely divided 

 gold, in the percentages used by us, in ice makes little or no 

 difference in its dielectric power when cooled to the tempera- 

 ture of liquid air. 



(ii) The presence to about the same extent of the hydrates of 



potassium, sodium, rubidium, or the oxides of copper, iron, 

 or lead, causes a very great increase in the dielectric power 

 of the ice at that low temperature. 



(iii) The dielectric curves are, however, all seen to be tending 



downwards in such a way as to show that at still lower tem- 

 peratures it is probable the effect of the oxides or hydrates 

 would be annulled and the dielectric constants of all be 

 reduced to a value not far from that of pure ice. 



(iv) The exception to this tendency, so far as yet observed, appears 



to be in the case of the oxide of copper, which, when sus- 

 pended in ice, causes it to possess the remarkably high 

 dielectric value of 150 even at the temperature of liquid air. 



