Constant of Ice and Alcohol at very Low Temperatures. 3 



Table I. — Determinations of the Dielectric Constant (Specific 

 Inductive Capacity) (K) of Water by Various Methods. 



Observer, 



Reference. 



Value 

 found. 



Method. 



W. Nernst . . . 



C. B. Thwing 



L. GTraetz and 

 L. Fomm 



T. F. Smale .. 



F. Heerwagen 



j A. Franke. . . . 



W.KKontgen 

 E. B.Kosa .. . 



'Zeits. phys. Chem.,' 

 1894, vol. 14, pp. 

 622—633 



'Zeits. phys. Chem.,' 

 1894, vol. 14, pp. 

 286—300 



'Wied. Ann.,' 1895, 

 vol. 54, pp. 626—640 



'Wied. Ann.,' 1896, 

 vol. 57, pp. 215—222 



'Wied. Ann.,' 1893, 

 vol. 49, p. 279 



Wied. Ann.,' 1893. 

 vol 50, p. 163 



Wied. Ann.,' 1894, 

 vol. 52, pp. 593—606 

 Phil. Mag.,' 5th ser., 

 vol. 31, 1891, p. 188 



80-00 at 

 17° C. 



755 

 73-54 



80-05 



80-88 at 

 17° C. 



81-65 at 

 17°C. 



86-0 



75-7 at 

 25° C. 



By condensers balanced on a 

 Wheatstone's bridge ar- 

 rangement using a tele- 

 phone as detector. 



By resonance of two electrical 

 circuits. Capacity in each 

 adjusted to identity. 



By deflection of a dielectric 

 ellipsoid suspended in water 

 in an electric field. 



By using an electrometer 

 tilled with water. 



By using a double electro- 

 meter, one filled with water, 

 Reversals of polarity 42 — 85 

 per second. 



By using a double electro- 

 meter and reversals of pola- 

 rity made by an induction 

 coil. 



By alternate currents and 

 condenser. 



By attraction of plates of a 

 condenser, alternating po- 

 tentials used. 2000 to 4000 

 reversals per minute. 



The general results show that the square root of the specific in- 

 ductive capacity of water as determined by relatively slow-speed 

 electrostatic methods is expressed by a number which is not very 

 different from that which denotes the refractive index of water for 

 electrical waves varying in length from 8 mm. to 600 cm. Max- 

 well's law is, therefore, fulfilled in the case of water under these 

 conditions. 



The general evidence at disposal does not indicate any very 

 marked dispersive power on the part of water for electric waves 

 varying in length between the above-named limits ; though the care- 

 ful results of P. Drude in 1896, for waves from 40 to 200 cm. in 

 length, taken by themselves, indicate a slight normal dispersion, 

 the refractive index increasing with decreasing wave-length. Change 

 of temperature has a marked effect upon the electrical refractive 

 index, and conclusions cannot be drawn, therefore, from the com- 

 parison of observations not made at the same temperature. 



There is, however, no such good agreement between the results 

 of these two classes of physical measurement in the case of ice. 



b 2 



