EXPERIMENT

• Objective
  To find out how the solution of the different substances found in our future soaps affects the growth and mortality of bacteria. The main point, is to investigate the antibacterial effect of these soaps.

• Materials:

-       735 g of fat

-        250 g of coconut oil

-        15 g of wax of bee

-        Caustic soda

-        Scale

-        thermometer

-        gloves

-        knife

-        Phenolphthalein 

•  Variables:

• Independent: Amount of fat added to the soap. This variable will be measured in grams using a scale.   
• Controlled: The temperature at 54 degrees centigrades. This variable will be measured with a thermometer.
• Dependent:

• fat solving power: depends on the amount of fat added to the soap.
• Inactivation of viruses, bacteria, yeasts, and endotoxins power: depends on the amount of NaOH added to the soap.

• Qualitative: the soap mixture will change colour depending on the substances that we add progressively and the heat that is being applied in the different steps of the procedure.

• Method

1. Weight 139 grams of NaOH carefully,  because it’s a reactive and unstable material. Also it combines very quickly with liquids, absorbing the humidity of the air too. It is highly corrosive and irritating when it is in contact with the skin.
2. Add NaOH in 300g of water

• For safety, do it outdoors. Taking in consideration the smoke and the heat (about 80ºC), that it will produce.
• Always pour the caustic soda in the water, never in reverse. We need cold water.
• Mix up with a wood spoon. In a few minutes the mix should be clear for the next step.

     C.    Saponification:

• Heat the fat mixed until it has melted. Maintain the temperature at 54.
• The fat must be melted but not hot and water should be the same temperature.
• Add 15 grams of beeswax.
• Remove the water from the caustic soda in fat.
• Remove the soap in one direction and very slowly pour the water from the caustic soda in the oil.

      D.   Kneaded:

• While the soap is mixing we will notice that is changing its colour and consistency becoming whiter and creamier.
• Now we add some colourings, flavouring and others to give it different qualities.

       E.   Molded:

• Put a layer of cellophane so that it excels in the bottom of the mold; this will help to remove the soap later. Use a big spoon and spatula, and pour the soap on the tray.
• 1-24h after making the soap, cut it in pieces and let it dry in an open space.
• Check the soap’s pH, as it should be between 7 and 10. Use a few drops of phenolphthalein.

BACKGROUND INFORMATION

BACTERIA

Bacteria are unicellular prokaryotic organisms; they lack a nucleus. They have very short life spans varying between minutes and days. Bacteria are the oldest living beings on Earth and they can be found everywhere even on the air we breathe.

Bacteria have a very fast reproduction process and that’s the reason of its short life span. They reproduce asexually by binary fission. (Microinmuno.qb.fcen.uba.ar, 2014)

The necessary conditions for a suitable culture of bacteria are: temperature, amount of humidity, pressure, light, gas presence, the sterility of the means and acidity. It has to contain the necessary nutrients, growth factors and be extent of pollutant microorganisms.

SOLUTION

A solution is a homogeneous mixture of two or more substances. The solutions are formed by the solute and the solvent (usually a lesser amount solute solvent).

Solution = solute + solvent

• Solute: A substance that is dissolved in another.
• Solvent: A substance or liquid capable of dissolving a body or other substance (the solute).

Example: A sugar cube in a glass of water. Sugar would solute and solvent water.

(Chem.purdue.edu, 2014)