78 
MK. P. V. JBEVAN ON THE COMBINATION OF HYDROGEN 
Pringsheim’s explanation, however, of the hydrogen and chlorine reaction is not 
tenable, as when we have free atoms it is hardly conceivable that the complicated 
action, requiring the meeting of five molecular systems, should occur, and not the 
direct combination of hydrogen and chlorine atoms. 
Another explanation'^ of the action of water vajjour is that hydrogen peroxide is 
formed by direct oxidation of the water molecule, and that this gives up some oxygen 
to the other substance taking part in the action. This view is only apj^licable to 
oxidation and not to such actions as the combination of sodium and chlorine, which 
does not occur in the absence of moisture. 
This view may, however, be extended, and we may suppose that intermediate 
compounds, which are purely additive, are formed, and which break down into more 
stable forms, giving the final result of the action. This hypothesis will be further 
developed after we have discussed the experimental investigation of the combination 
of hydrogen and chlorine. 
II. Experimental In v^estigation. 
For the experimental part of this investigation the method of Bunsen and Koscoe 
was in main followed for the study of the initial exj^ansion, or Drajjer eftect, and the 
period of induction. The mixture of gases was prepared by electrolysis of ordinary 
pure hydrochloric acid saturated with hydrochloric acid gas. It has already been 
remarked that oxygen has been supposed to occur in the gases prepared in this v-ay, 
but this quantity of oxygen is, at any rate, extremely small and seems to be without 
effect; otherwise it seems inqiossible to explain the constancy of the results obtained 
by this method, when we remember the large effect produced by the addition of a 
very small quantity of oxygen. At any rate, the difficulty of preparing a pure 
mixture of separately formed gases in the right proportions is so great, that the 
electrolytic method is far superior to any other. 
Several forms of cell for electrolysis were tried. Platinum electrodes are dissolved 
after some time, so that carbon rods were used, as it was found that they lasted for a 
long period. The form of vessel adopted consisted of an ordinary lamp chimney sealed 
to a three-way tap leading to a thistle tube and to the insolation apparatus. The 
carbon electrodes were fitted through an indiarubber stopper, through which also 
passed a tube connected with a tap through which the spent acid could be removed 
while fresh acid was introduced through the thistle tube. In this way there was no 
fear of introducing air into the apparatus when recharging the cell. Above the 
stopper a layer of paraffin wax was melted so as to form a paraffin bottom to the cell. 
This paraffin, after the cell had been in use for several weeks, was apparently 
unaffected by the acid itself or the chlorine in solution. The cell was continually 
* Mendeleeff, ‘ Principles of Chemistry,’ L, p. 305. 
