to the Contact of Gases with Liquids. 75 



I could not attempt to base a calculation on so uncertain a 

 quantity. 



To get over this little trouble I set up five Grove cells in 

 series, which gave a deflexion either way of 40 scale-divisions. 



Therefore, 



187x5 



40 

 1-8x18-7x5 



= T>. P. in Grove cells. 

 D. P. in volts. 



4 

 42-08 = D. P. in volts. 



The other numbers given were found in the same way. 

 The potential of an electrified body depends on conditions, 

 and the quantity I have determined may not be what I repre- 

 sent it. At all events, I have found approximately the 

 potential above earth of a point in space immediately above 

 the surface of the hydrochloric acid, through which hydrogen 

 is passing. The distance between the surface of the acid and 

 the drops where they broke away separately was 2 inches. 

 If this distance were lessened another source of error would 

 arise (or increase), for the particles of acid propelled by the 

 hydrogen from the acid generator would strike the stem of 

 the funnel and lessen the electrification, because, as has been 

 proved, they are opposite in sign to the escaping gas. 



But to return to my proposed straightforward experiment. 

 I had intended to pass a current of neutral hydrogen through 

 a column of strong hydrochloric acid, but found it impossible 

 to neutralize the gas from a generator. However, I had now 

 by trial become aware that a flask of hydrogen w T ould become 

 neutral after the lapse of some hours. 



Three half Winchester quarts were filled with hydrogen by 

 the displacement of water from a generator containing zinc 

 and HOI, and were left during the night to lose their charges. 

 At 8 o'clock the next morning one was uncorked and placed 

 on the insulated plate. The hydrogen escaped, but the spot 

 did not move. I was then pretty certain that the gas in the 

 other two vessels was neutral. 



A beaker, 7 inches high and 2 inches in diameter, was 

 nearly filled with strong HC1, and a very slender delivery- 

 tube, which had been attached to one of the vessels containing 

 the hydrogen, was placed in it in such manner that any gas 

 escaping from the vessel should pass right through a column 

 of acid 6 inches high. An inverted metallic goblet was now 

 attached to the insulated plate and quadrants, and placed in 

 such position that any hydrogen issuing from the beaker eon- 



