Disinfectants Bacterial Growth Science Project

Science Fair Project Idea - Use of disinfectants and antiseptics.

Certain substances are used to prevent the growth of bacteria.Make a list of substances that you know are used for this purpose.

The way in which they affect the growth of bacteria may be found out by the following experiment.

Science Experiment - Disinfectand and Antiseptic Creation and its Effect on Bacterial Growth

Into each of several test tubes pour about 10 cc.Of unsterilized beef tea culture medium.

To one add 3 cc.Of carbolic acid 5 % solution.

To another add 3 cc.Saturated solution of boracic (boric) acid.

To another add 3 cc.1-1000 solution of mercury bichloride.

To another add 3 cc.Hydrogen peroxide.

To another add 3 cc.Tincture of iodine.

To another add 3 cc.Formaldehyde, 4%.

To the others add 3 cc.Different disinfectants.

To one add nothing.

After four or five days examine all the test tubes and record the results.

A distinction is usually made between antiseptics and disinfectants.An antiseptic is a substance that will check or retard the growth of bacteria, but does not destroy them.A disinfectant, or germicide, is a substance that kills bacteria.Some substances may be classed under both heads ; a strong solution of it acting as a disinfectant, a weak solution acting only as an antiseptic.Salt, sugar, spices, and vinegar may be considered antiseptics that are harmless when taken into the body with food.With the exception of the use of one tenth of one per cent of benzoate of soda, other antiseptics are not permitted to be used for the preservation of food.

The more important germicides are tincture of iodine; carbolic acid (5 to 10 per cent solution) ; mercury bichloride (1 part to 1000 or 1500 parts of water) ; chloride of lime, and formaldehyde.These are all highly poisonous when swallowed, and great care should be taken that they are not placed where they may accidentally be -used in this way.

Boracic acid is a mild antiseptic which is frequently used as an eye or mouth wash.Hydrogen dioxide (peroxide), when it has not been allowed to remain exposed to the air, will destroy germs.It has the advantage of being non-poisonous, but it has the disadvantage of losing its value if kept in a bottle which is not well corked.

Make sure you also study penicillin and other antibiotics and how they were discovered. This will give you extra points in your science project!

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