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Discovering natural fibres: Preparing Solutions

Iodine Stock Solution

In a 500 ml stoppered bottle, make a saturated aqueous solution of potassium iodide, then use a spatula to add a few crystals of the element iodine (some crystals may not dissolve, do not worry). Insert the stopper and shake. Top up with demineralised water, shake again and store.

Label carefully including instructions.

This makes a concentrated stock solution that will provide iodine solution for quite a few years. When the crystals are finally dissolved simply add more water.

To Use:

Pour off a little of the dark solution into a beaker and dilute with water until it is translucent. Provide the dilute solution in labelled dropper bottles for student use.

If not using for a while decant the solution and wash the bottles or the rubber tops will deteriorate. Refill when required.

Starch Solution

If this is needed, mix a teaspoonful of flour or cornflour (corn starch) with water to make a creamy slurry in a 500ml beaker, pour in about 100ml boiling water and stir vigorously. The mixture should become translucent. It does not need to be very concentrated, if is the colour will be almost black instead of an obvious blue. Test a little with iodine solution and dilute if necessary. The starch solution will not keep more than a week in the refrigerator.

Biological Stains

Some Common Biological Stains - from CR Scientific, search for methylene or scroll down to see the instructions


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