hydrogen then passes through conduit 41 which connects with duct 34 where the hydrogen will be diluted below its explosive limit by the large volume of air swept across the electrolyte the hydrogen is thus scrubbed before it is diluted with air which means that a smaller volume of gas requires treatment furthermore as hydrogen is about 7 as dense as air the de mister is more efficient than if air were mixed with hydrogen before de misting the cell is provided with a feed solution inlet 42 which is illustrated as communicating with the cooling and concentration chamber 18 but which could be located at either chamber there is also an acid feed line 43 for the purpose of adding sufficient acid to maintain a constant ph the product of the electrolysis is removed through drain 44 in operation the electrolytic solution circulates in the direction shown by the arrows in fig1 and 2 due to the gas lift effect of the hydrogen evolved in the electrolysis the heat generated during electrolysis is removed by the combined effect of the air sweep passing countercurrent to the direction of flow of the electrolyte as described above together with the auxiliary cooling coils 38 at the same time the air causes evaporation and consequent concentration of the electrolytic solution fig4 illustrates a further embodiment of the invention in which the cell chamber 50 is entirely separate from cooling and concentration chamber 51 the electrolyte flows through line 52 from chamber 50 to 51 and returns through line 53 the hydrogen gas generated.