1887.] 



On Antimony Pentachloride. 



379 



force of terrestrial magnetism, have electric currents circulating in 

 them. 



The difficulty against this supposition always seemed to me to lie 

 in the fact that the electromotive forces required to start a current 

 were larger than those which could possibly exist in the atmosphere. 

 But as there are very likely continuous electric disturbances going on, 

 such as we observe in aurora? and thunderstorms, the regions within 

 which these discharges take place would act as conductors for any 

 additional electromotive force however small, so that any regular 

 motion, such as tidal motions, could very well produce periodic effects 

 affectingf our magnetic needles. 



If these original discharges increase in importance, then, according 

 to the results obtained in this paper, the currents due to the smaller 

 periodic causes would increase also, and they may increase in a very 

 rapid ratio. We know that the electric discharges in the upper 

 regions of the atmosphere are considerably stronger at times of many 

 sunspots, and this may account for the fact that at those times the 

 amplitude of the daily oscillation of the magnetic needle is consider- 

 ably increased. 



I have had considerable assistance in these experiments from my 

 assistant, Mr. Stanton, to whom my best thanks are due. 



XL "Contributions to our Knowledge of Antimony Penta- 

 chloride." By Richard Anschutz and P. Norman Evans. 

 Communicated by Prof. A. W. Williamson, For. Sec, R.S. 

 Received May 5, 1887. 



Some months ago* we showed that antimony pentachloride can 

 be distilled, undecomposed, under much diminished pressure ; our 

 next step was the attempt to determine the vapour-density under 

 similar conditions. The fact that the boiling point of antimony penta- 

 chloride lies much lower than that of the trichloride would seem to 

 show that the vapour-density of the pentachloride, as in the case of 

 the trichloride, corresponds to the simpler formula. Nevertheless, 

 on account of the fundamental importance which the establishment of 

 the simple formula SbCl 5 would have for the valence of antimony, 

 it seemed indispensably necessary to make a determination of the 

 vapour-density.' We will preface our further observations with the 

 remark that we have not yet succeeded in determining the vapour- 

 density of antimony pentachloride under diminished pressure ; how- 

 ever, in the course of many unsuccessful attempts which we have 

 made to this end, we had one point thrust on our notice, which on 



* ' Chem. Soc. Journ.,' vol. 49, 1886, p. 708. 



