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Minor Versionm

by Procheta Mallik


Commercially, sodium hydroxide is made through the electrolysis of a brine solution. Here, we do the same, albeit on a much smaller scale, to make your own sodium hydroxide, the quintessential base, with Hydrogen and Chlorine as byproducts.

    • Exercise caution while handling scissors/cutters or any sharp object.

    • Do not ingest any of the chemicals

    • Excessive exposure to chlorine gas may lead to nausea, vomiting, headache, etc. While smelling chlorine, inhale it just enough to test it's presence.

    • Wash the hands properly after using any chemicals.

  1. Cut a 4 cm piece from a fat straw.
    • Cut a 4 cm piece from a fat straw.

    • Seal one end of the cut straw with the tape, as shown.

    • Completely seal one end of the straw; this is your `measuring cup'.

    • Your measuring cup will hold 2.5 g to 2.75 g of salt in it.

    • Add two cups of common salt (NaCl) in the measuring cup and add it to a cut bottle.

    • Add around 70 ml of water to the NaCl. You may use the 30 ml bottles provided to estimate the amount of water you add.

    • Use markings on the container to measure the quantity of water to take

    • Stir the contents to make NaCl Solution.

    • Wash the containers thoroughly with water before starting the process.

    • Take a 30 ml container and mark 2 cm from the bottom.

    • Make a hole at the mark using scissors. Make the hole big enough so that a straw can snugly fit inside it.

    • Repeat the same with the other container.

    • Take a stiff straw (or thin rubber/plastic pipe) and mark 4 cm from one end of it.

    • Cut the straw at the marking.

    • Insert a cotton ball of pea size into the cut straw.

    • Insert the straw into the container.

    • Glue the straw to the container.

    • Insert and glue the other end of the straw to the hole of the other container.

    • Add the prepared NaCl solution to either of the containers. Note that the level in the containers is automatically the same!

    • Your apparatus is now set up, as shown.

    • Using the dropper add few drops of Bromothymol blue indicator to both the containers.

    • Go to DIY Battery Holder to make one of your own and use it here.

    • Connect the negative terminal of the battery to the iron nail.

    • Make sure to wash the iron nail initially to remove the greasy layer from it.

    • Connect positive terminal of the battery to a pencil lead (graphite).

    • Your electrodes' set up looks like this.

    • Now insert the iron nail in one container and the graphite rod in the other.

    • Observe the color change in both the containers after some time.

    • Once the color in the container with iron nail turns blue, dip the red litmus and observe the color change of the litmus paper.

    • Dip a pH paper into the container with the iron and observe and note down the pH based on the colour of the pH paper

    • Liquid coming out of the container(s) after inserting the straw.

      • While making hole in the container please verify repeatedly to check the size of the hole with the straw (or pipe).

    • Electrolysis not started, change in colour not happening nor bubbles emanating.

      • Check for the electrical connections.

    • Change in red litmus and pH paper colour not visible.

      • Wait for few more minutes to check for the colour change.

    • Note down the time at which electrolysis started and at what time solution at iron electrode turn blue completely.

      • Record this time in the first column of observation table.

    • Using the pH paper find out the pH of NaOH solution prepared at Iron electrode using the pH scale chart.

      • Repeat it after every 15 mins and record your findings in observation table.

    • Vary the concentrations of NaCl and compare the time taken for colour change.

    • Replace iron nail electrode by graphite rod.

    • Place two iron nails and two graphite rods instead of one.

    • Replace two AA cells by one 9V battery.

Finish Line

Attached Documents

Vishal Bhatt

Member since: 04/26/2017

2,329 Reputation

63 Guides authored