"Transfer-resistance " in Electrolytic Cells. 



131 



It had a slightly concave bottom, and was placed in a flat- 

 bottorned glass basin 12'0cm. in diameter. It was closed 

 air-tight by a perforated indiarubber bung, having a narrow 

 horizontal glass tube, open at both ends, fixed in it. The 

 tube had an internal diameter of about 2*0 mm.; it was pro- 

 vided with a small divided scale, and contained a minute drop 

 of water to act as an index of the expansion or contraction of 

 the enclosed air (see sketch). 



After ballasting the bottle by means of a heavy ring of 

 glass encircling its neck, the electrolyte was poured into the 

 glass basin up to a height of 3'0 cm. A sheet of platinum 

 8*0 cm. x 15*5 cm., with its largest dimension horizontal, was 

 placed vertically in the liquid to act as an anode. Under 

 these circumstances the amount of external surface of the 

 platinum bottle in contact with the liquid, excluding that of 

 the bottom, was about 40*0 square centimetres, whilst that of 

 the front side of the sheet of metal was about 46*5 sq. cm. 

 These several conditions, and the distance of the sheet from 

 the bottle, were kept the same in each experiment. 



In some preliminary trials, using a current from a battery 

 of six pairs of zinc and platinum in dilute sulphuric acid, in 

 single series, and a large anode of zinc instead of the platinum 

 one, — on passing the current through a mixture of one volume 

 of sulphuric acid and one hundred of water, into the bottle, 

 whilst much hydrogen was evolved at the cathode, a small 

 expansion of the air in the bottle at once occurred, and moved 

 the index forward 1*0 mm. in about two or three seconds. 

 The current was then stopped, and the index returned to its 

 former position in about one minute. The piece of zinc was 

 then replaced by a platinum wire which was brought into 

 contact with the bottom of the bottle, and the circuit again 

 closed. The current now circulating was about the same in 



K2 



