Copper(II) citrate: synthesis and decomposition

An interesting experiment with copper(II) citrate

In to­day’s pro­gram: a cool ex­per­i­ment with cop­per(II) cit­rate!

Safe­ty pre­cau­tions

Warn­ing! Only un­der adult su­per­vi­sion.


  • hot so­lu­tions of cop­per(II) sul­fate and sodi­um cit­rate;
  • beaker;
  • fun­nel;
  • fil­ter pa­per;
  • Petri dish;
  • sheet of met­al;
  • match­es;
  • pa­per sten­cil.

Step-by-step in­struc­tions

Add a hot so­lu­tion of sodi­um cit­rate to a hot so­lu­tion of cop­per(II) sul­fate. Ob­serve as a cop­per(II) cit­rate pre­cip­i­tate grad­u­al­ly forms. Fil­ter it out and leave it to dry for 24 hours – it will turn into a beau­ti­ful turquoise pow­der. Ar­range it in a pa­per sten­cil on a sheet of met­al and touch it with a burn­ing match. The cop­per(II) cit­rate will grad­u­al­ly turn black.

Process de­scrip­tion

When heat­ed, cop­per ions are re­duced, tak­ing elec­trons from cit­rate ions, and turn into very small par­ti­cles of metal­lic cop­per. Un­like a siz­able piece of cop­per, these par­ti­cles are eas­i­ly ox­i­dized by at­mo­spher­ic oxy­gen, re­leas­ing heat and form­ing black cop­per(II) ox­ide. The heat this gen­er­ates keeps the process go­ing, so even a small amount of heat is enough to cause the de­com­po­si­tion of the en­tire cop­per(II) cit­rate pile.

A sim­i­lar ex­per­i­ment is in­clud­ed in the “Cop­per” set from the MEL Chem­istry sub­scrip­tion! You can choose amaz­ing chem­istry sets and get them on a month­ly ba­sis for your kids.