Energy Relations of Certain Detectors. 533 



association on the validity of the relation is examined and 

 it is shown that with associated liquids the calculated value 

 of the latent heat may be either greater or smaller than the 

 actual observed value. 



The relation combined with Trouton's equation gives the 

 simple relation 



T = K v^V, 



where T is the boiling-point, V the molecular volume at the 

 boiling-point, and K is a constant. This relation gives a 

 fairly constant value of K for the members of an homologous 

 series, but its value varies rather considerably from one 

 homologous series to another. The relation is also greatly 

 affected by molecular association, the value of K always 

 being much greater for associated liquids than the average. 



The Chemical Department, 

 The University, Manchester. 



LI 1 1. The Energy Relations of Certain Detectors used in 

 Wireless Telegraphy. By W. H. Eccles, D.Sc, A.R.C.S* 



[Plate X.] 



THE results of an experimental examination into the 

 physical properties of four very different types of detector 

 used in radio-telegraphy are set forth briefly in the following 

 pages. The conditions of the experiments have been made 

 generally identical with those arising in the ordinary employ- 

 ment of the detectors, and, in particular, the quantities of 

 energy given to the instruments, in the form of electrical 

 oscillations, have been of the same order in these experiments 

 as in actual practice. The detectors investigated are the 

 electrolytic, the carborundum rectifier, the zincite detector, 

 and a thermoelectric detector. All these have before this 

 been subjected to close scrutiny by various observers, who, 

 however, used methods different from that of this paper ; a 

 summary of their work will be given alongside the results of 

 the present experiments. These results, it will be seen, are 

 expressed in the form of curves rather than as tables of 

 figures ; each curve may be regarded as typical of the 

 detector concerned, and has been selected from a number 

 of curves drawn from measurements accumulated during 

 last year. 



The method and apparatus used are the same as were 

 described in a paper " On Coherers,' 3 read before the Physical 



* Communicated by the Physical Society : read July 8, 1910. 



