Chlorine — the gas artist

How chlorine can change the color of a drawing

Usu­al­ly, when we talk about artists, we think of peo­ple like Dali, Pi­cas­so and Munch, but among the chem­i­cal el­e­ments there are those who can draw!

Safe­ty pre­cau­tions

Warn­ing! Ob­serve safe­ty rules when work­ing with these sub­stances. Wear pro­tec­tive gloves, glass­es, and a mask.


  • beaker;
  • sodi­um chlo­ride;
  • sodi­um hy­dro­gen sul­fate;
  • man­ganese(IV) ox­ide;
  • wa­ter;
  • potas­si­um io­dide so­lu­tion;
  • thy­mol blue so­lu­tion;
  • heat­ing de­vice;
  • fil­ter pa­per;
  • cot­ton swab or brush.

Step-by-step in­struc­tions

Mix sodi­um chlo­ride, sodi­um hy­dro­gen sul­fate, man­ganese(IV) ox­ide and wa­ter in a glass and mix thor­ough­ly. Draw some pat­terns on a fil­ter pa­per with so­lu­tions of potas­si­um io­dide or thy­mol blue. Place the fil­ter pa­per on top of the beaker of sodi­um chlo­ride so­lu­tion and heat the beaker gen­tly. Grad­u­al­ly, the draw­ings change col­ors!

Process de­scrip­tion

When a mix­ture of sodi­um chlo­ride, sodi­um hy­dro­gen sul­fate, man­ganese ox­ide(IV) and wa­ter is heat­ed, chlo­rine gas is re­leased. The re­leased gas dis­solves in the wa­ter from the so­lu­tions the draw­ings are made of. When a so­lu­tion of potas­si­um io­dide comes into con­tact with chlo­rine, as a more ac­tive halo­gen, chlo­ride ions dis­place io­dine ions, and molec­u­lar io­dine is re­leased and the pat­tern turns brown. When chlo­rine dis­solves in the wa­ter of the thy­mol blue so­lu­tion, it dis­pro­por­tion­ates, or it is ox­i­dized and re­duced to hy­drochlo­ric HCL and hypochlor­ous HOCl acids, which change the acid­i­ty of the so­lu­tion and thy­mol blue changes from or­ange to pur­ple col­or.

A sim­i­lar ex­per­i­ment is in­clud­ed in the “Hy­dro­gen and Chlo­rine” set from the MEL Chem­istry sub­scrip­tion!