Effluvia from Chemical or from Voltaic Reactions. 29 



effect; the liquid is negative in both cases. The human breath, 

 although containing visible fog as well as gas resulting from 

 chemical action in the lungs, does not appear to be sensibly 

 charged. 



19. From considerations connected with the first series of 

 experiments in this paper, as described in § 3 to § 11, it was 

 thought worth while to try whether there was any similar 

 electrification of a liquid from which gas was evolved by the 

 current from a separate battery as in the voltameter, and 

 some experiments were made with this object. 



The battery and decomposing-cell were arranged on an 

 insulating stand and connected to the electrometer. Some- 

 times the mixed gases were evolved from platinized platinum 

 electrodes in dilute acid ; sometimes one or the other gas was 

 absorbed by suitable arrangements. I was, however, unable 

 to arrive at any general law governing either the sign of the 

 electrification or its rate of increase. The latter varied from 

 one division per minute to ten or even twenty times as much 

 in the same time. In a majority of cases the evolution of the 

 mixed gases electrified the cell negatively, and where either 

 oxygen or hydrogen was evolved alone by the use of a double 

 fluid arrangement the cell became positive ; but there were 

 exceptions to both rules. The question as to the cause of this 

 electrification is very interesting, and I hope it will not 

 remain long unanswered. 



20. Mr. Enright's remark near the end of his paper on the 

 improbability of the so-called "air effect" having any con- 

 nexion with the theory of the galvanic cell (referring, I 

 presume, to the supposed contact-action between metals and 

 air or free oxygen), prompts me to point out that what I 

 believe will be ultimately adopted as the true theory of Volta's 

 fundamental contact-experiment, or at least the first hint of 

 this theory, was given by De la Hive*; and considerations 

 relative to its further elucidation and support will be found in 

 papers by the present writer in vol. xli. of the Proceedings of 

 the Eoyal Society, and in vols. vi. and vii. of this Journal. 



My best thanks are due to Professors Everett and Letts, of 

 Queen's College, Belfast, for permission to use the apparatus 

 of the College in these experiments, and for suggestions and 

 advice during the investigation. 



Summary of Conclusions. 

 When gas is evolved in a chemical or voltaic reaction, the 

 effluvium (i. e. this gas or something carried up with it) is 



* Traite de V Electricity t. i. p. 776. 



