Soap from bacon - the dangers of alkaline solutions
Demonstrations designed to capture the student's imagination
In this demonstration raw bacon is used to show the effects of acid and alkali on living tissue, and also the formation of soap from hydrolysed fat.
Hydrolysis of fats and muscle
Fats and oils are naturally occurring esters derived from propane-1,2,3-triol (glycerol), combined with long-chain carboxylic acids (fatty acids).
The first part of this demonstration involves hydrolysing the ester linkages in the fats and separating the fatty acids from the propane-1,2,3-triol. Under basic conditions this reaction is known as saponification. Muscle tissue comprises mainly proteins, which themselves are derived from amino acids linked together by peptide links (-CO-NH-). These peptide links, like the ester links in fats, undergo hydrolysis, forming the constituent amino acids.
In the second part of the demonstration sodium chloride is used to precipitate the dissolved sodium salts of the fatty acids released from the bacon fat boiled in the alkali solution. Adding sodium chloride as another solute in the solution affects the solubility of the sodium salts of the fatty acids, which are less soluble in what is now a brine solution - this effect is known as salting out. On cooling the sodium salts of the fatty acids precipitate as soap.
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