PROFESSOR H. B. DIXON ON THE RATE OF EXPLOSION IN GASES. 169 
for the exit tube. The electrolytic gas entered through one tube, while hydrogen 
was driven from a holder through the other. 
At the further end of the explosion tube the gases passed through (1) a wash 
bottle ; (2) a long graduated tube fitted with taps at either end ; (3) a thin glass 
bulb; (4) a tower filled with lime and powdered charcoal. The thin bulb could be 
readily detached and submitted to a “magnesium flash.” The graduated tube served 
to analyse the gas. It was connected with a movable reservoir from which a solution 
of caustic potash could be introduced into the tube. The volume of chlorine present 
could thus be readily estimated, the residual hydrogen being measured under atmo¬ 
spheric pressure by bringing the level of the liquid in the tube and reservoir to the 
same height. 
The current for the electrolysis was given by 7 secondary cells (Elwell and 
Parker), E.M.F. 13-15 volts ; current 4-G amperes. The preliminary saturation 
occupied many hours. It was found best to leave a small current (about ^ ampere) 
passing through the cell for two days before making an experiment. When the 
liquids were all saturated it took about four hours to fill the explosion tube. An 
analysis of the issuing gas at the end of that time gave— 
Chlorine.49'8 2 
Hydrogen ..... 50T8 
In another experiment an analysis at the end of 4^ hours gave— 
Chlorine. 49'90 
Hydrogen.50 TO 
Part II .—Arrangement of the Firing Tubes. 
The leaden pipes used for the explosion tubes were 5, 6^, 9, and 13 mm. in 
internal diameter. The pipe was wound on a galvanised iron drum about 2 feet in 
diameter, provided with a flange at the bottom. 
In order to wind the pipe it was first laid straight along a corridor. The drum A 
was attached to a turntable B fixed to a low trolley, which was pushed forward as 
the pipe was wound on the revolving drum. 
The drum with the pipe wound on it was placed in an iron watei’-bath, wdiich 
could be heated by a large ring burner. The ends of the pipe passed out through two 
openings near the top of the bath. To each end of the explosion tube was soldered a 
short steel tube, ending in a cap with a polished steel face 30 mm. in diameter, 
perforated in the centre by a hole 10 mm. in diameter. The steel face of each cap is 
pressed by a clamp against a similar steel face, as in Begnault’s gas apparatus, from 
which these joints are taken. One end of the explosion tube is thus joined to the 
MDCCCXCIIT.—A. Z 
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