Linette Guare

Chemical Flower Garden

Concept:

To show the formation of precipitates assisted by an osmosis reaction.

Materials:

• glass jar or large beaker
• tweezers or tiny spoon
• 300 mL water
• 150 mL sodium silicate
• Chromium chloride (green) solid
• Ferric chloride (orange) solid
• Aluminum potassium sulfate (white) solid
• Cobalt chloride (purple) solid

Directions:

1. Mix the sodium silicate with the water into the glass jar.

2. Add a pinch of each of the four types of crystals into the glass jar.

3. Do not shake or mix the solution. The "flowers" will begin to grow.

Introductions:

I just love flowers, but they die so quickly, plus they take too long to grow, and now is not a good time of year to try growing them. So I decided to find a better way to have a flower garden right before our very eyes.

Explanation:

Certain crystals form precipitates when placed in the water glass (sodium silicate solution). In this case, stalagmites (like those found in caves) form from the bottom of the jar up - these are metal ion silicates.

The process of osmosis is also taking place. The water travels through the semi-permeable membrane of the metal ion sodium silicate precipitate to the higher level of the metal ions that are present on the inside. The water pushes into the gel like structures, which then fills the gel with water. The crystals form and the membranes burst which create new ones and the process keeps going allowing the crystals to keep growing upward and side ways.

Safety Precautions: Be careful when working with the crystals, especially the chromium chloride.

Waste Disposal: If placed in a glass jar, a lid can be place on it to save it. If a beaker is used, careful pour liquid down the drain and the metal crystals should be kept for toxic waste disposal.

Reference: Summerlin, L, Ealy, J, Chemical Demonstrations, American Chemical Society, 1985, p. 30.