This generator was simply a reincarnation of the chlorine generator built previously. Both anode and cathode were steel, separated by a fibreglass diaphragm. The electrolyte consisted of concentrated sodium hydroxide (lye) and was operated on the 5V rail of a computer power supply (measured electrode voltage was ~3.5V, measurement of the current was impractical although would have been >10A). The hydrogen gas was collected above the catholyte, passed through a wash bottle and then collected in inflatable plastic bags. The anolyte was simply vented to atmosphere. A disadvantage of this setup is the gas pressure acting on the anolyte and catholyte must be approximately equal as a positive back pressure on the catholyte (eg required when inflating a balloon) may cause the overflowing of the electrolyte from the cell.
See chlorine generator for a picture of the cell.
The 6mm vinyl tubing from the wash bottle was attached to a syringe body, around which the base of the bag was wrapped and secured with an elastic band. This arrangement produced quite a good gas seal between the bag and the tubing.
The first bag tried was a standard 63 x 91 cm garbage bag, which from memory was sufficiently buoyant to lift a mass of about ~40g. This bag took about 4 hours to fill. Next tried was the larger wheelie bin liner bag (the exact size of which I cannot remember, but may however be estimated from the photo). This bag took just over 24 hours to fill and was neutrally buoyant with a load of 245g.
This bag was released with no load into the atmosphere and due to it's large size was visible for quite some distance.
