1893.] 



The Electrolysis of Steam. 



95 



fused up ; wires connected to the electrodes c, d are fused through the 

 closed ends of these tubes. It is desirable that the closed ends of the 

 tubes h, h should come up as close as possible to the exits /, g, as air 

 is very apt to remain in the tube if there are any places through which 

 the steam does not rush. The tubes h, h may either be fused on to 

 the spark tube or fastened to it by rubber tubing. 



The delivery tubes P, G (fig. 2) are fused on to the discharge tube 

 at/, g (fig. 3). These tubes are about 5 cm. in diameter and terminate 

 in narrow openings. It is essential that the steam and the mixed 

 gases should escape through the tubes P, G at approximately the 

 same rate ; to ensure this, the narrow extremities of these tubes should 

 be equal both in length and width. This was attained by drawing 

 out a piece of tubing which was originally of the same diameter as 

 F, G, and then cutting it at the middle of the narrow part ; the two 

 halves were then either fused or fastened by rubber tubing to P, G. 

 The narrow ends of P, G are turned up and placed under mercury 

 in the vessel M (fig. 2). Over these ends, graduated eudiometer tubes 

 are placed ; these are filled with mercury at the beginning of the 

 experiment, but the mercury soon gets displaced by the water pro- 

 duced by the condensation of the steam rushing through the tubes. 



The heat produced by this condensation serves a useful purpose ; it 

 raises the temperature of the water in the eudiometer tubes over 

 which the gases are collected to over 80° C., and thus, since hot water 

 absorbs oxygen but not hydrogen much less readily than cold, dimin- 

 ishes the disturbing effect due to the greater absorption of the oxygen 

 than of the hydrogen by the water over which the gases are collected. 



The effect produced by electrification on the condensation of a jet 

 of steam is shown in a very striking way by this apparatus. When 

 the delivery tubes are open to the air, the steam, after escaping from 

 the nozzles, goes some inches before it condenses sufficiently to form 

 a cloud ; as soon, however, as the coil is turned on and the sparks 

 pass, brownish clouds reaching right down to the nozzles are at once 

 formed. The cloud is denser in the steam which has gone past the 

 negative electrode than in that which has gone past the positive. 



Precautions which it is necessary to take to ensure Correct Results. 



These can, perhaps, best be realised by considering that what we 

 have to measure is the excess of hydrogen or oxygen, as the case may 

 be, left after exploding the mixed gases. Now, if we consider, firstly, 

 that this excess is a small fraction of the original volume of the 

 mixed gases — the exact proportion between the two varies greatly 

 with the length of the spark, but in some cases the excess did not 

 amount to more than 5 per cent, of the mixed gases; secondly, 

 that only a very small portion of the steam passing through the 



