Specific Inductive Capacity and Latent Heat. 113 



resistances. Thus a single platinum thermometer will do the 

 work of a whole series of mercury thermometers, and that 

 with far greater accuracy and without the necessity of 

 applying any troublesome and uncertain corrections. 



It may be objected that the use of a platinum thermometer 

 requires electrical apparatus and some knowledge of electrical 

 measurement. I quite admit that it requires some special 

 skill and experience to make a good thermometer, but the 

 rest of the apparatus required is obtainable in almost any 

 laboratory, and it is easy to take the readings quickly and 

 accurately after a little practice. The great superiority of 

 the platinum thermometer in range, accuracy, and durability, 

 will be found in the end to save so much time and expense as 

 will more than compensate for the small trouble of learning 

 to use it. 



XVIII. On a probable Relationship between Specific Inductive 

 Capacity and Latent Heat of Vaporization. By Eugene 

 Obach, Ph.D.,F.C.S* 



THE discovery of a near relationship between physical 

 constants hitherto considered independent of each other 

 seems of sufficient interest to merit a place in the Philosophical 

 Magazine, notwithstanding that the experimental data which 

 can be brought forward in support of such relationship are 

 somewhat meagre and not particularly accurate. 



I have recently been led to investigate whether specific 

 inductive capacity and latent heat of vaporization of a 

 liquid are in any way related to each other, and I find this 

 actually to be the case, at least as far as certain series of 

 chemically related organic compounds are concerned, viz. the 

 esters of formic, acetic, and benzoic acid, and the monatomic 

 alcohols. For these bodies, as will be shown hereafter, 

 inductive capacity and latent heat are directly proportional. 



The numerical values of these two physical constants ob- 

 tained by different observers are in many cases very discordant ; 

 and it was therefore considered desirable to adhere as far as 

 possible to the figures given by one and the same authority, 

 and to introduce those of others only where absolutely 

 necessary. 



The specific inductive capacities here adopted are those 

 published by S. Tereschin f in 1889, and the latent heats of 



* Communicated by the Author. 



t Wied. Annul, vol. xxxvi. pp. 792-804 (1889). 



Phil. Mag. S. 5. Vol. 32. No. 194. July 1891. ' I 



