When the electrolysis was still a child…The funnel and the two single-mouthed cylinders were initially filled with slightly acidulated water (a small amount of sulphuric acid). In each cylinder was set a platinum electrode. As the contraption was connected to a battery and current began to flow, in the cylinder with the negative electrode twice as much gas formed as in the other one. Hydrogen on the negative side, oxygen in the positive one, quod erat demonstrandum…