Illustrated Guide to Home Chemistry Experiments

380 DIY Science: Illustrated Guide to Home Chemistry Experiments

SBSTITUTIU oNS ANd modIfICATIoNS

• You may substitute any containers of similar size for the
  beakers.


• You may substitute a 10 mL Mohr or serological pipette
  or a disposable plastic pipette for the syringe.


• You may substitute about 11 mL of concentrated (18 m)
  aqueous ammonia for the 8 g of sodium hydroxide. If you
  use aqueous ammonia, add only a sufficient amount to
  precipitate all of the copper present as the powder-blue
  copper salt. As you add aqueous ammonia to the copper
  sulfate solution, you’ll notice a very dark blue coloration
  appear where the ammonia contacts the copper sulfate
  solution, but that dark blue disappears as the solution is
  mixed. Add ammonia only until the dark blue color first
  begins to persist in the solution.

CUTIOA nS

Concentrated aqueous ammonia is corrosive and

produces strong irritating fumes. Sulfuric acid and sodium

hydroxide are corrosive. Copper sulfate is moderately

toxic. Wear splash goggles, gloves, and protective clothing.

z

LABORATORY 21.2:

pRodUCE RAyoN fIBER

In this lab session we produce rayon, the

first practical artificial fiber. We use the word

“artificial,” because rayon is neither a natural

fiber nor a synthetic fiber. What other option

is there? Half and half. Rayon, first produced

commercially in 1899, is actually a semi-

synthetic or reconstituted form of the natural

polymer cellulose.

RIREEqU d EqUIpmENT ANd SUppLIES

£ goggles, gloves, and protective clothing

£ balance and weighing papers

£ beaker, 250 mL

£ beaker, 600 mL

£ Erlenmeyer flask, 250 mL

£ graduated cylinder, 100 mL

£ filtering funnel and support

£ stirring rod

£ syringe, plastic, 10 mL to 50 mL

£ filter paper (5 pieces)

£ stopper, solid (to fit flask)

£ copper sulfate pentahydrate (25 g)

£ sodium hydroxide (8 g)

£ aqueous ammonia, concentrated (70 mL)

£ sulfuric acid, ~1.5 m (~300 mL)

£ crushed or chipped ice (~75 mL)

Rayon was first produced commercially using the
cuprammonium process, a process that is still in limited
use today but has been largely supplemented by alternative
processes that are more environmentally friendly. In the
cuprammonium process, which we use in this lab session,
solid cellulose (such as paper or wood chips) is dissolved in
Schweizer’s Reagent, a coordination compound of copper(II)
hydroxide in aqueous ammonia. The cellulose is then
reconstituted by reacting the tetraamminecopper(II) hydroxide
solution with an acid, to neutralize the ammonia and destroy
the coordination compound that makes cellulose soluble. The
cellulose precipitates as a solid.

POCEDURER
Perform this lab under an exhaust hood or in a well-ventilated
area to dissipate the fumes of concentrated aqueous ammonia.

1. If you have not already done so, put on your splash
   goggles, gloves, and protective clothing.


2. Weigh out about 25 g of copper sulfate pentahydrate and
   transfer it to the 250 mL beaker. Add about 100 mL of
   water and swirl or stir until the copper sulfate dissolves
   completely. (This is a nearly saturated solution; you may
   warm the solution to dissolve the copper sulfate faster.)


3. Transfer about 50 mL of water to the 250 mL Erlenmeyer
   flask and sufficient crushed or chipped ice to bring the
   total volume to about 125 mL. Weigh out about 8 g of
   sodium hydroxide and transfer it in small portions, with