Posted by Jana on Sunday, September 17, 2006 at 8:54pm.
I have to create a 5-layer density column, using liquids that are not flammable or chemicals, so basically you have to be able to eat or drink it to use it in the column. I only have three layers so far: water, vegetable oil, and corn syrup.
Obtain a clear plastic container whose size meets your needs, and carefully add appropriate amounts of the
following materials in the order specified (the first material listed is the most dense, and should be added first:
water -- color with an appropriate amount of food color before pouring
canola oil -- don't add food color (it won't dissolve in oil)
60% isopropyl alcohol -- you can buy 70% isopropyl at drug stores and grocery stores -- it's used as
rubbing alcohol and disinfectant -- you then have to dilute it to make it 60% -- add 2 ml of water
to every 10 ml of alcohol, or 20 ml of water to every 100 ml of alcohol -- before pouring, color
with an appropriate amount of food color different from the first one
mineral oil -- baby oil is mineral oil, and can be used here, but ordinary mineral oil is easily obtained at
pharmacies and is cheaper -- don't add food color (it won't dissolve in oil)
91% isopropyl alcohol -- you can buy 91% isopropyl at most drug stores, and sometimes at grocery
stores -- it's used as a disinfectant, particularly for pierced ears -- before pouring, color with an
appropriate amount of food color different from the previous two
â€¢ Layers should probably be a minimum of about 1/2 inch thick, and pouring should be gentle, to avoid a layer
falling through the layer it is being poured on and interacting with the layer below that one. If the container is
small, consider using a pipette or eyedropper. This is easier than pouring, and allows you to add the liquids very
slowly and gently to prevent unwanted mixing.
â€¢ Sometimes the material the container is made of plays a role in how well the layers form, possibly due to
surface tension effects.
â€¢ Try tilting the container a little so that the liquid you are adding runs down the side more slowly. Or try laying
the new liquid very gently on the previous layer by having the dropper tip just barely above the liquid surface, so
that the new liquid doesn't fall and hit the surface hard.
â€¢ Donâ€™t use too much food coloring â€“ depending on the amount of liquid you are using, even one drop of food
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