How do you dissolve cellulose

5.1.1 Dissolving cellulose in s reagent

Material / chemicals:

  • Cotton wool
  • Cu (OH)2(harmful to health)
  • NH3 conc. (25%) (corrosive)
  • least. water

Equipment:

  • 2 beakers (400 ml)
  • spatula

Experimental setup:

Execution of the experiment:

  1. 3 g of cotton wool are placed in 100 ml of water
  2. 2 g Cu (OH)2 are dissolved in 105 mL ammonia. The result is a deep blue solution that s reagent.

3 g of cotton wool are added to Schweizer's reagent and the mixture is stirred until the cellulose has dissolved.

Observation:

A. The cellulose shows no visible change.
B. The cellulose dissolves. A deep blue, clear solution is created.

Explanation:

  1. The cellulose is insoluble in water because the cellulose chains are strongly connected by hydrogen bridges.

    The long cellulose chains combine to form crystal-like structures that water cannot dissolve. The water molecules penetrate between the cellulose chains - the cellulose swells - but do not bring them into solution.

  2. In Schweizer's reagent, the cellulose dissolves as a copper-cellulose complex. The Cu present in the solution2+-Ions with ammonia initially form the deep blue colored copper tetrammine complex [Cu (NH3)4]2+. At a high pH value, this reacts with the cellulose and breaks the hydrogen bonds between the cellulose chains.

    The crystal-like structures are broken down and water molecules can loosen the complexed cellulose chains.

Disposal information:

The copper cellulose solution and its residues are disposed of in the heavy metal waste.

Tips:

  • All devices that have come into contact with the copper cellulose solution are cleaned with diluted ammonia before rinsing with water, as otherwise insoluble cellulose residues can form.
  • The experiment should be carried out near the table fume cupboard, as the ammonia odor that arises can be very unpleasant.

Video clip:

You can watch the demo video here:


5.2.2 Production of a regenerated cellulose film using the copper silk process


© 2001Markus Förg, [email protected]