When soup is made in a pre-industrial process, animal fat is boiled with water that has been steeped with wood ash. Use the internet or book sources to find out why the wood ashes are needed, and whether the pH of the water is acidic, basic, or neutral.

Question

Chemistry

Alec Peck

14 April, 20:13

When soup is made in a pre-industrial process, animal fat is boiled with water that has been steeped with wood ash. Use the internet or book sources to find out why the wood ashes are needed, and whether the pH of the water is acidic, basic, or neutral.

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Answers (1)

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Shyla Baxter · Answer 1

Wood ashes are needed to supply the caustic potash (potassium hydroxide) needed for saponification to take place. And the PH of the water is basic because potassium hydroxide is a base.

Explanation:

Saponification is the process of soap making and another name for alkaline hydrolysis of fats and oils.

Vegetable oils or fat undergo hydrolysis:

I. Acid hydrolysis to yield fatty acids and alkanol.

Vegetable oil/fat + H2O (from acid) = Alkanoic acid (fatty acid) + alkanol

II. Alkaline hydrolysis to produce soaps and alkanol. Example:

Glyceryltristearate + caustic soda = Sodium stearate (soap) + glycerol.

Caustic soda (NaOH) is used to produce harder soaps while caustic potash (KOH) is used to produce softer soaps.

A solution of wood ash can be used instead of KOH for the production of softer soaps because it is rich in KOH.