Equivalents of Oxygen and Hydrogen. 615 
waste space F at the top of the wide tube, as the electrolyte 
rises in temperature considerably during passage of the 
current. 
Fig. 1. 
J 
The connecting tubes G Gr are about 1 mm. in bore, but 
there is an enlargement H to catch drops of electrolyte 
projected upwards by the current of gas. K is a side tube 
for introducing the electrolyte, and is closed by a rubber 
tube and glass stopper. 
M I is a gauge to show when the gas in the measuring-tube 
-is at the pressure of the atmosphere. Mercury, water, and 
olive oil were tried in this gauge, and the last found to be 
much the best. The gauge-tube is about 6 mm. in bore, and 
no error due to capillary action could ever be detected when 
oil was used. The gauge should be rather long, as when the 
,gas to be measured is left for some time in the apparatus 
there is a risk of oil being sucked into the coulometer, in 
2T2 
