+----------------+-----------+------------+ | Substance. | K | K | | | at 15° C. | at -185°C. | +----------------+-----------+------------+ | Water | 80 | 2.4 to 2.9 | | Formic acid | 62 | 2.41 | | Glycerine | 56 | 3.2 | | Methyl alcohol | 34 | 3.13 | | Nitrobenzene | 32 | 2.6 | | Ethyl alcohol | 25 | 3.1 | | Acetone | 21.85 | 2.62 | | Ethyl nitrate | 17.7 | 2.73 | | Amyl alcohol | 16 | 2.14 | | Aniline | 7.5 | 2.92 | | Castor oil | 4.78 | 2.19 | | Ethyl ether | 4.25 | 2.31 | +----------------+-----------+------------+ The above determinations at low temperature were made with either a steady or a slowly alternating electric force applied a hundred times a second. They show that the dielectric constant of a liquid generally undergoes great reduction in value when the liquid is frozen and reduced to a low temperature.[13] The dielectric constants of gases have been determined by L. Boltzmann and I. Klemencic as follows:-- TABLE IV.--_Dielectric Constants (K) of Gases at 15° C. and 760 mm. Vacuum = 1._ +---------------------+------------+------------+------------+ | | Dielectric | | Optical | | Gas. | Constant | [root]K. | Refractive | | | K. | | Index. | | | | | [mu]. | +---------------------+------------+------------+------------+ | Air | 1.000590 | 1.000295 | 1.000293 | | Hydrogen | 1.000264 | 1.000132 | 1.000139 | | Carbon dioxide | 1.000946 | 1.000475 | 1.000454 | | Carbon monoxide | 1.000690 | 1.000345 | 1.000335 | | Nitrous oxide | 1.000994 | 1.000497 | 1.000516 | | Ethylene | 1.001312 | 1.000656 | 1.000720 | | Marsh gas (methane) | 1.000944 | 1.000478 | 1.000442 | | Carbon bisulphide | 1.002900 | 1.001450 | 1.001478 | | Sulphur dioxide | 1.00954 | 1.004770 | 1.000703 | | Ether | 1.00744 | 1.003720 | 1.00154 | | Ethyl chloride | 1.01552 | 1.007760 | 1.001174 | | Ethyl bromide | 1.01546 | 1.007730 | 1.00122 | +---------------------+------------+------------+------------+