How to Make Chlorine Gas


Introduction: How to Make Chlorine Gas

A lot of you probably know electrolysis with water. In this instructable I am going to show you how to take electrolysis to another level, with chlorine gas as a product.

Step 1: Safety Instructions + Theory

WARNING! Chlorine Gas is toxic and this experiment should be performed outside or under a fume hood. Please wear safety gear and stop the experiment once you smell the chlorine (should be after some seconds). Now a little theory (can be skipped if you like). Salt in Water dissolves into positive sodium ions and negative chlorine ions. With the electrolysis in this experiment we will obtain the chlorine gas as the chlorine ions are attracted to the positive electrode and leave one of their excess electrons, thus forming chlorine gas. On the negative side, hydrogen gas will form.

Step 2: The Materials

Now you need to gather some easy-to-find materials.

  • A Cup
  • Water
  • Salt
  • Aluminium Foil
  • A carbon or graphite electrode (can be obtained from batteries or just use a pencil lead)
  • Wires
  • A 9 Volt Battery
  • (Duct) Tape
  • Breadboard (optional)
  • something to stir
  • safety gear

Step 3: Prepare the Solution

Dilute some salt in water. You can decide how much salt to use. I used 3-4 teaspoons of regular Sodium chloride salt on 100 ml of water.

Step 4: Prepare the Electrodes

Wrap a wire around the carbon electrode and fix it with tape. Repeat the process with the aluminium foil.

Step 5: Connecting - Producing Chlorine Gas

Put both electrodes in the cup filled with the saltwater. Now connect the positive side of the battery with the carbon electrode and the negative side with the aluminium foil. For ease of use you may use a breadboard. Once connected to the power outlet bubbles will start to form. The ones on the carbon electrode are chlorine gas bubbles. Soon you should be able to smell the chlorine. Stop the experiment then and do not leave it unattended, as chlorine is toxic. I am not responsible for any damage caused by the recreation of this instructable.



    • Oil Contest

      Oil Contest
    • Woodworking Contest

      Woodworking Contest
    • Clocks Contest

      Clocks Contest

    We have a be nice policy.
    Please be positive and constructive.




    How to create large amount of chlorine gas ? I want to experiment and store the gas

    You will get both gases, as the chlorine ions will be attracted to the positive electrode. But you are right, about the hydrogen gas. You get both.

    Yeah, this will make hydrogen gas and chlorine gas, right? If they are exposed to heat, like around 250 degrees celsius, they WILL form hydrogen chloride, which is poisonous to say the least. What I mean by that is that there is NO cure for hydrogen chloride poisoning. And as well as this the hydrogen chloride will react with the atmospheric humidity and form hydrochloric acid. Again, not might but WILL form it. So learn the theory, sure, but just don't do it. Please.

    I used to take bleach at 5% and heat it in a flask with sulfur (with a hot water bath) and yes the amount of chlorine that was given off was huge. So I would control the heat by keeping the solution below 75 degrees C and made sodium sulfide.

    If you want to make sodium sulfide this may be a method but BEWARE of all the CHLORINE. This is EXTREMELY DANGEROUS if not done properly. Do at your own RISK.

    Sodium sulfide reacts with many strong acid to produce deadly hydrogen sulfide gas too.

    Maybe instead of lye you could use sodium thiosulfate. Yes it convert any bromine into bromine salts. It less dangerous that using lye with electrolysis. The Kbr or NaBr could be made OUTSIDE with a glass seperation funnel with 3 moles per L (500 ml) sodium thio sulfate.

    Maybe you could try making bromous acid or putting small amounts less than 1 g in 500 ml of potassium bromide and adding lye. Then add electricity. Yes Bromine and Lye produce NaOBr which is a disinfectant. It may be dangerous SO only due it outside if you have a professional background in chemistry.

    what is the reason for this instructable? chlorine gas is not something that should be taken lightly and has an exceptionally irritating character which can rapidly harm a person when inhaled in a strength of only 1 in 10,000 dilution breathing this with could possibly kill you, in an attempt to survive the poison chlorine gas a person breaths, the living tissue secretes a watery mucus trying to dilute the poison and protect the body in which case they could die, not from the poison its self but from drowning in their own fluids they secrete from the body trying to protect itself. this gas was used in ww1 by the Germans

    4 replies

    There is a clear warning. This is done every day at many public swimming pools. Also, I think the nazis used shoes, so we better stop wearing shoes.

    You should know that, in the swimming pool, the chlorine is in the form of liquid and it react with water to create a mild acid solution. That solution is disinfectable. You wont inhale too much chlorine gas at the pool, not as much as in your experiment. Please, use a gas mask each time you do this.

    ya swimming pools use chlorine as does every household but its not put under electrolysis you don't have kids turning it into a gas at the local swimming hole but after this instructable you might find one harmed thinking its a "cool" experiment with no real benefit other than watching some bubbles and choking. and when's the last time you heard anyone killed by a shoe? I like your whole theory on it though didn't make sense but you're sarcasm is priceless

    I thought that it was interesting to see what could be made of ordinary substances like kitchen salt. I am aware of the risks of chlorine gas and I think this Instructable contains enough warnings for anyone wanting to recreate it.

    I'm just wondering; Is there any particular reason I would want to make chlorine gas? Liquid chlorine, sure.. sure.. But gas? Just as an experiment?

    1 reply

    I thought that it was interesting to see what could be made of ordinary substances like kitchen salt. Of course there are a lot of things that can be done with Chlorine Gas (none of them should be done at home e.g. making Hydrogen Chloride) but in this case it was just ment as an experiment.

    Thanks for all the warnings. They are very necessary.
    Good job explaining!

    Great in depth instructable