Exercise 14 Micro Lab: Hand Washing
Temporary microorganisms removed before you begin a laboratory session as they may contaminate your cultures
Long term flora that generally inhabit hair follicles and sebaceous glands of your skin and remain after thoroughly washing, scrubbing, and disinfecting your hands
Any cleansing solution, including soap that can be used to remove bacteria embedded in fats and oils
Process whereby a soap is formed when fats are heated in the presence of a base such as sodium hydroxide. The sodium salt (Na + RCOO-) of the acid (RCOO-) is the "soap."
Why don't we just use water to wash our hands?
While water can remove dirt, it is ineffective in eliminating bacteria suspended in fats, hydrocarbon chains, and other water-insoluble substances.
How does soap clean?
Each soap molecule has a long hydrocarbon chain (R) attached to a negatively charged carboxylate ion (COO-) and its associated sodium (Na+) ion.
In greasy, bacteria laden water, the hydrocarbon end of the soap molecule is soluble in oils and the carboxylate end is soluble in water. A chemical link forms between oil and water as the oily ends of the molecules dissolve together. Greasy oil is combined with water and can be carried away in the liquid.
Why is soap not an effective cleansing agent when used with hard water?
When soap is used with hard water, magnesium and calcium salts react with soapy oil droplets forming a lighter than water scum that adheres with grease and bacteria to whatever is being washed.
water containing mineral salts