COLLOIDAL SULFUR

PURPOSE

The purpose of this activity is to prepare a colloid and observe its properties.

DESCRIPTION

This activity is appropriate for a general or first-year college-prep course. A "milk of sulfur" colloid is prepared and can be used to demonstrate the diffusion of light and non-separation of colloidal dispersions.

TIME REQUIRED

Approximately 30 minutes.

MATERIALS

Chemicals:

powdered sulfur*
methyl alcohol
water

Equipment: filter paper

funnel
test tube
centigram balance

*See Modifications / Substitutions

HAZARDS

Methyl alcohol is flammable and poisonous; avoid skin contact. Goggles must be worn throughout the activity.

MODIFICATIONS/SUBSTITUTIONS

1. Sulfur is available from a drugstore as flowers of sulfur. It may also be purchased as commercial garden sulfur from a garden shop or nursery.
2. Methyl alcohol, also known as methanol, can be found in many schools as duplicator fluid.

PROCEDURE

1. Dissolve 0.1 to 0.2 grams of powdered sulfur in 3 to 5 mL of methanol.
2. Shake the preparation for several minutes, then filter it, catching the filtrate in a test tube containing approximately 15 mL of water. This will produce a sulfur-methanol-water colloidal system.
3. Observe the system. Shine a light through the colloid and observe the dispersion of light.
4. Allow the mixture to stand and observe that the colloidal suspension does not settle.

DISPOSAL

The preparation can be flushed down the drain with plenty of water.

DISCUSSION

This activity can be used to study colloidal systems including their dispersion of light and the Tyndall effect. Additionally, it can be used in conjunction with solutions and suspensions to study the similarities and differences among them.

REFERENCES

Suerth, S. Margaret, Science Teacher's Workshop, May,1968. A similar experiment is described in this article.

Submitted by S. Margaret Suerth