Intelligence and Miscellaneous Articles. 519 



zero, so as to annul the electromotive force, I left the bismuth 

 cylinder in the same position as before between the poles of the 

 electromagnet, and then weakened the compensating-pile so as to 

 have in the circuit a current of about the same intensity as in the 

 first experiment. Experimenting then as in the first case, I found 

 that the magnetism exerted no influence on the intensity of the 

 thermoelectric current. 



In these preliminary experiments I made no measurements which 

 would enable me to give definite values of the variation found. In 

 order to furnish an approximate idea, I may mention that in the 

 conditions in which 1 experimented the diminution of the thermo- 

 electric electromotive force was about -J^. The variations in ques- 

 tion are perhaps of the same order of magnitude as those found by 

 Eighi for the electrical resistance. 



In a more complete investigation of the phenomenon, which I 

 hope presently to carry out, I shall examine the relation between 

 the intensity of the magnetic field and the thermoelectric power of 

 pure and commercial bismuth in various states of aggregation, and 

 of the alloys of bismuth. 



I propose to make an analogous investigation on antimony. — 

 Rendiconti delta R. Accademia dei Lincei, February 1887. 



ON THE ACTION OF LIGHT ON A MIXTURE OF HYDROGEN 

 AND CHLORINE. BY E. PRINGSHEIM. 

 The author sums up as follows the results of his investigation: — 



(1) The proof attempted by Bunsen and Eoscoe that in the 

 photochemical combination of chlorine and hydrogen, an amount of 

 work is done by light for which an equivalent quantity of light 

 disappears does not hold. The proof for that assertion lies in the 

 fact that the quantity of the hydrochloric acid formed is propor- 

 tional to the intensity of the light. 



(2) The first apparent action of light on chlorine and hydrogen 

 consists in a sudden increase of volume of the gaseous mixture, 

 which as suddenly disappears ; the magnitude of this increase is 

 proportional to the intensity of the acting light, but is independent 

 of the condition of the induction and of the quantity of hydro- 

 chloric acid formed. 



(3) This sudden increase of volume is produced by a sudden 

 dissociation of the molecules, which goes on at the moment of 

 chemical change. 



(4) In this, no hydrochloric acid is formed in the first case, but 

 an intermediate substance. 



(5) The slow formation of hydrochloric acid by light takes place 

 solely with moist chlorine and hydrogen ; dry gas is not affected by 

 light which is not very intense. 



(6) Under the influence of strong sources of light or great heat, 

 dry hydrogen and chlorine gases explode as well as moist. 



(7) The intermediate product which the photochemical indica- 

 tion produces, and the assumption of which completely explains 

 this phenomenon, arises very probably from decomposition of 

 aqueous vapour. — "Wiedemann's Annalen, November 1887. 



