d ELECTROLYSIS In aqueous solutions there are usually four ions present two from the water and two from the dissolved salt The products will be gaseous or metals which are deposited on the negative electrode It is composed of an open cylinder of glass approximately 8 cm high and 25 cm in diameter A small bottle of similar size with the bottom cut off would do just as well The cylinder has a 2hole rubber stopper carrying two carbon electrodes with connecting leads to a battery or DC supply of 4 to 6 volts If cork is used this must be made leak proof by covering the whole of the bottom surface round the electrodes and the glass edge with Faradays wax or a similar soft wax The electrodes may be carbon rods from a dry cell or pencil leads The alloy supports for the coiled filament in electric light bulbs have also been found suitable for electrodes The electrodes should project about 2 cm into the cylinder and also 2 cm below for attaching the leads to the battery Pencil leads are brittle and if they are used it is better to fix the electrodes in the following way Solder a piece of stout copper wire to a 4 cm length of braided copper screening wire Drill two holes in the rubber stopper with a 1 mm drill Insert the copper wire into the hole from above and pull it right through the stopper until the screening wire is also pulled a little way into the hole Into the core of this screening wire insert the pencil lead securely Then pull the screening wire with the lead further into the stopper so that the lead electrode is firmly held in the stopper The excess copper wire is cut off This procedure is repeated with the other electrode The solution is placed in the glass cylinder The two small tubes are then filled with the solution and carefully inverted over the electrodes The electrodes are connected to a safe DC supply with a small bulb in series Increase the voltage until the bulb lights showing that a current is flowing When this happens cut out the bulb from the circuit by closing the switch as shown This will allow a larger current to flow The tubes collect any gas given off and the properties of the gas should be tested Using carbon electrodes the following results will be found