Magic liquid

How can you turn a yellow solution into a whole rainbow?

Safe­ty pre­cau­tions

Warn­ing! Only un­der adult su­per­vi­sion.


  • 5 dis­pos­able cups;
  • thy­mol blue so­lu­tion;
  • sodi­um hy­dro­gen sul­fate so­lu­tion;
  • cit­ric acid so­lu­tion;
  • sodi­um car­bon­ate so­lu­tion;
  • sodi­um bi­car­bon­ate.

Step-by-step in­struc­tions

Pour into 5 sep­a­rate glass­es: a so­lu­tion of sodi­um hy­dro­gen sul­fate, a so­lu­tion of cit­ric acid, a 1:1 mix­ture of cit­ric acid and sodi­um car­bon­ate so­lu­tions, a so­lu­tion of sodi­um car­bon­ate, and sodi­um bi­car­bon­ate. Then, dis­trib­ute some thy­mol blue equal­ly into each glass. This cre­ates a rain­bow!

Process de­scrip­tion

Acid-base in­di­ca­tors are sub­stances that change col­ors de­pend­ing on the pH of the so­lu­tion they’re in. Thy­mol blue is one such in­di­ca­tor. As it in­di­cates, the sodi­um hy­dro­sul­fate so­lu­tion is strong­ly acidic (pH <1), the cit­ric acid so­lu­tion is acidic (pH ≈ 2 in the vial), the mix­ture of cit­ric acid and sodi­um car­bon­ate so­lu­tions is in the mid­dle (3 <pH <8), the sodi­um bi­car­bon­ate so­lu­tion is slight­ly al­ka­line (pH ≈ 9), and sodi­um car­bon­ate is strong­ly al­ka­line (pH> 10). You can also use thy­mol blue to test liq­uids you have around your house, such as lemon juice, soap, milk, and many oth­er prod­ucts and house­hold chem­i­cals.

This and oth­er amaz­ing ex­per­i­ments are wait­ing for you in the MEL Chem­istry sub­scrip­tion!