144 PROFESSOR H. B. DIXON ON THE RATE OP EXPLOSION IN GASES. 
far as I know the rate of explosion of hydrogen and chlorine had never been 
measured. 
Before devising ap})aratus to carry out the experiments, it was necessary to deter¬ 
mine whether the action between hydrogen and chlorine was a direct one, or whether 
it was influenced by the presence of other gases, e.g., steam.* * * § Electrolytic hydrogen 
and chlorine were accordingly sealed up in glass vessels with anhydrous phosphoric 
acid, and were kept in the dark for several weeks. The dried gases were found to be 
far less sensitive to the action of light than when a trace of aqueous vapour was 
present, a result in accordance with Pringsheim’s t observations. But on the 
passage of an induction spark by means of platinum-iridium wmes the dried gases 
exploded violently. 
Since these experiments left it doubtful whether the presence of steam influenced 
the rate of explosion of hydrogen and chlorine, a preliminary series of measurements 
were made with the dry and moist gases.]; The explosion-vessel consisted of two 
long glass tubes § (34 and 30 feet) cemented together. The ends were provided with 
steel flanges so that they could be rapidly joined to two smaller tubes which carried 
the silver bridges. The explosion tube was hung to the wall of a long, darkened 
corridor. 
The gas passed directly from the electrolytic cell through washing tubes into the 
long explosion tube—driving out the air before it: at the further end it passed 
through an “ analyser,” which served to determine the composition of the mixture 
issuing from the tube. When the long tube was completely filled with hydrogen and 
chlorine, the two smaller tubes carrying the bridges were fastened to its two ends by 
the steel flanges. These smaller tubes had previously been filled with hydrogen and 
oxygen. The electric connections were then made to the chronograj)h, and the gases 
fired by the passage of a spark through the hydrogen and oxygen in one of the 
smaller tubes. The flame travelling down this tube, which was about 4 feet long, 
broke the silver bridge at the end of it, and communicated the explosion to the 
hydrogen and chlorine. On reaching the end of the glass tube, the flame broke the 
silver bridge carried by the second smaller tube. In the few seconds that elapsed 
between the joining on of the small tubes and the firing of the mixture but little 
diffusion of the gases was possible ; and the silver bridges, being coated with 
paraffin, were hardly acted on by the chlorine. By this arrangement the electrolytic 
hydrogen and chlorine were kept from contact with metals or india-rubber, and 
* “ On the Combination of Hydrogen and Chlorine, alone, and in Presence of other Gases.” By 
H. B. Dixon and J. A. Harkeb. ‘ Manch. Memou’s ’ [IV.], vol. 3, p. 118. 
t ‘ Annalen der Physik,’ N.F., vol. 32, p. 421, 1887. 
t ‘Manch. Memoirs’ [IV.], vol. 4, p. 3. (The numbers given in this paper were afterwards found 
to be affected by a constant error.) 
§ These glass tubes were made for me by Messrs. Molineaux and Webb, of Manchester. They were 
nnannealed, but stood the shock of many explosions. 
