“Artificial silk” experiment
How to make artificial silk from cotton wool
It’s become fashionable to say that we eat nothing but chemicals nowadays. But we also wear “chemicals”, as it happens! In this interesting experiment you’ll find out how to make artificial silk.
Wear protective gloves and glasses and work in a well-ventilated room.
Reagents and equipment:
- 20 g of copper hydroxycarbonate;
- 50 ml of 25% ammonium;
- 2M solution of sulfuric acid;
- cotton wool (cellulose).
In the beaker, dissolve copper hydroxycarbonate in ammonium. Then pour the mixture into another beaker, to remove the remains on the undissolved salt. Place the cotton wool in the resulting bright blue solution and observe it dissolve. Draw the solution into the syringe and squeeze the contents into the solution of sulfuric acid. Blue threads form which turn white over time.
When a solution of copper salts reacts with ammonium, copper ammine forms, which has a very interesting property–it can dissolve cellulose, with the formation of a complex compound of copper, ammonium and cellulose. If this complex is squeezed into a solution of sulfuric acid through a syringe or straw, the complex breaks down, and viscose is formed in thin threads, from which the artificial fabric cupro or artificial silk is made.