We used electrolysis (with sodium hydroxide NaOH solution as the basic medium) to produce oxyhydrogen and extinguished the candle by means of the reaction between hydrogen and oxygen.
When electrolyzed, water decomposes into two gases: oxygen O2 and hydrogen H2. The end result is twice as much hydrogen as oxygen. Such a mixture of gases is called oxyhydrogen. When a bottle full of oxyhydrogen is placed near a burning candle, the gas ignites immediately and blows out the candle.
Simon also performed two more experiments to purify water (from heavy metals using resin and organic pollutants using activated coal).