On the Salts of Tetrethylphosphonium. 183 



rent to concentrate itself towards the exterior*. In general 

 both causes must cooperate to produce an apparent increase 

 of resistance to variable currents. 



When the magnetic circuits are open, as with bars of iron 

 of moderate length, the reaction of the iron manifests itself 

 mainly as increased self-induction. This happens also in the 

 case of closed magnetic circuits, when the magnetic changes 

 are very small. 



In general, since the curve of fig. 2 differs widely from an 

 ellipse, the reaction of the iron cannot be fully represented as 

 equivalent to a change in the resistance and self-induction of 

 the magnetizing circuit. In any case of strict periodicity the 

 reaction may, however, be analyzed, in accordance with 

 Fourier's theorem, into harmonic components with periods 

 which are submultiples of the original period. The neigh- 

 bourhood of iron may thus introduce overtones into what 

 would otherwise be a simple sound. 



Terling Place, Witham, Essex, 

 July 4. 



XXII. On the Salts of Tetrethylphosphonium and their De- 

 composition by Heat. By Prof. B. A. Letts, Ph.D., Sfc y 

 Queen's College, Belfast, and ISTokman Collie, Ph.D., 

 Science Lecturer, The Ladies' College, Cheltenham^. 



ONE of us (in conjunction with another chemist) has already 

 pointed out the very striking analogies which exist 

 between the elements phosphorus and sulphur and their com- 

 pounds Xj an( i we were anxious to continue our experiments 

 in connection with this question. 



The action of heat on methyl-sulphine compounds has been 

 studied by Crum Brown and Blaikie § , who have shown that 

 they decompose in a perfectly simple and definite manner. 

 We were accordingly desirous of ascertaining whether 

 the analogous phosphorus derivatives, namely the salts of 

 tetrethylphosphonium, would behave similarly. 



We had already investigated the action of heat on some of 

 the salts of tetrabenzylphosphonium ||, but the results were 



* "On the Self-induction and Resistance of Straight Conductors," 

 Phil. Mag. vol. xxi. (1886) p. 388. 



t Communicated by the Authors. 



X Crum Brown and Letts, Trans. Roy. Soc. Edin. vol. xxviii. p. 571 j 

 and Letts, Trans. Roy. Soc. Edin. vol. xxviii. p. 583. 



§ Crum Brown and Blaikie, Journal/, prakt. Chemie [2] xxiii. p. 395. 



|| Letts and Collie, Trans. Roy. Soc. Edin. vol. xxx. part i. p. 181. 



