Electrodes for electrochemical cells

Oxygen is hazardous when in contact with flammable substances, particularly oil. No oil or other organic substance should be allowed to come into contact with oxygen under pressure. Oxygen lines, valves, and regulators must be kept scrupulously free of oil. 

We describe below the electrodeposition procedures required in the preparation of the platinum and silver- silver chloride electrodes used in electrochemical experiments. We shall not attempt to give a general treatment of electroplating or of electrode preparation. Further details can be found in various monographs.  

Platinum Electrodes. Platinum electrodes are used in conductivity cells and in hydrogen electrodes. For these purposes they are usually covered with a deposit of platinum black to increase the surface area. For certain other purposes, such as use in redox electrodes, this is usually not necessary. 

Platinum can be used in the form of thin sheet or screen. Platinum wire can be welded to a small square of sheet or screen by placing it in position on a metal surface, heating to red heat with a torch, and striking lightly with a small ball peen hammer. The platinum wire can then be sealed into the end of a piece of soft-glass tubing. Electrical contact can be made by copper wire spot-welded to the platinum lead wire before the glass-to-metal seal is made. 

Platinum can be plated onto other metals by use of a solution containing 1 g platinum diammino nitrate, 1 g sodium nitrate, 10 g ammonium nitrate, and 5 mL concentrated ammonium hydroxide in enough water to make 100 mL of solution. The cleaned metal is made the cathode, and a strip of platinum metal is the anode a 4.5-V battery, a rheostat, and a milliameter are connected between the electrodes, and the plating is carried out at a current density of 50 to 100 mA per square centimeter of cathode surface. 

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