0.\ CHEMICAL COMlilNATlUN AND ELECTRIC DISCHARGE. 493 



wave were passing tlirougli a medium with a small number of free ions, the 

 effect of these ions would ho rather to affect the velocity of propagation than 

 to produce any great absorption. In the case of hydi'ogen at atmospheric 

 pressures we have seen that G.,t) is of the order 10'" ; in tliis ca.se j) would 

 have to be larger than 10'" to make the effects depending on du^ jdt lar<^e 

 compared with those depending on G.,pMi. We could not by discharfinf 

 Leyden jars get electrical vibrations of this rapidity, but at the pressure of 

 TTrioo of an atmosphere G.jp would only be of the order 10'', and we could 

 easily get electrical vibrations sufficiently rapid to make ]) large compared 

 with this quantity, and thus to make the effects depend chiefly upon the 

 term dujdf, that is, upon the inertia of the ions. 



The preceding experiments are, I think, sufficient to show the close 

 analogies existing between the phenomena of chemical combination and 

 of the electric discharge, and give hopes that the study of the passao-e of 

 electricity through gases may be the means of throwing light on the 

 mechanism of chemical combination. The work of chemists and physicists 

 may be compared to that of two sets of engineers boring a tunnel from 

 opposite ends- they have not met yet, but they have got so near together 

 that they can hear the sounds of each other's works and appreciate the 

 importance of each othei-'s advances. 



On the Electrification, of Molecules and Chemical Change. 

 Ihj H. Brereton Baker. 



[Ordered by the General Committee to be printed in extenso.'] 



More than twenty years ago a striking fact was discovered by Dr. 

 Wanklyn, that dried sodium could be melted in dried chlorine without the 

 production of the bright Hame usual under the circumstances. The action of 

 chlorine oil other metals in absence of moisture was investigated by Dr. 

 Cowper in 1876. He showed that in many cases the same result was 

 obtained as that of Dr. Wanklyn in the case of sodium. About this time 

 Professor Dixon, who was working on the rate of chemical change in a 

 mixture of carbon monoxide, hydrogen, and oxygen, was led to suspect the 

 great influence of the presence of moisture on the combustion of the 

 former gas, and he succeeded, by drying a mixture of carbon monoxide and 

 oxygen as completely as possible, in passing a stream of electric sparks in 

 the mixture without any explosion taking place. It was this experiment 

 which first led to the great interest taken by chemists in the influence of 

 moisture on chemical action. Many chemists have investigated different 

 chemical actions, and a large number of changes have been shown to be 

 dependent on the presence of moisture. A list of them will be found in a 

 paper on this subject in the ' Chemical Society's Journal ' of July last. It 

 seemed at one time to a chemist who was studying these actions, that no 

 chemical action could take place without the presence of moisture. As 

 action after action was investigated, and as new methods of purification 

 were introduced, further additions could be made to the list. I have 

 recently been engaged in studying several decompositions, however, and I 

 believe that although, in some cases, no breaking up of the molecules takes 

 place, as in the very interesting case of the action of heat on dried 

 ammonium chloride, in which no dissociation occurs, yet in some cases 

 action does take place. Potassium chlorate and silver oxide do decom- 

 pose, and give not atomic but molecular oxygen. Carbon bisulphide burns 



