Chemistry question about wood ashes and soap?
When soap is made in a pre-industrial process, animal fat is boiled with water that has been steeped with wood ash. Why are the wood ashes needed in this process and is the water acidic, basic, or neutral?
Making soap requires animal fat (not soluble in water) to be added to Lye (Sodium Hydroxide, a strong base). This adds a Na+ to the fat and makes the fat somewhat soluble in water. The Na+ part sticks out of the large organic part of the new molecule. This sodium is essentially polar and is attracted to water. The rest of the molecule (primarily fat) is essentially non-polar and is attracted to oily materials, like skin oils. This is what allows soap to remove dirt, this bridging between polar and non polar.
LeChatlier’s principle allows for a system to move away from a stress. Wood ashes tend to contain many minerals which have been absorbed by the tree while growing. This includes sodium. When the ashes are added to the brew, it forces the reaction to the right and produces more soap.
admin on October 29th 2009 in soap making process
MontyH responded on 29 Oct 2009 at 4:33 pm #
Making soap requires animal fat (not soluble in water) to be added to Lye (Sodium Hydroxide, a strong base). This adds a Na+ to the fat and makes the fat somewhat soluble in water. The Na+ part sticks out of the large organic part of the new molecule. This sodium is essentially polar and is attracted to water. The rest of the molecule (primarily fat) is essentially non-polar and is attracted to oily materials, like skin oils. This is what allows soap to remove dirt, this bridging between polar and non polar.
LeChatlier’s principle allows for a system to move away from a stress. Wood ashes tend to contain many minerals which have been absorbed by the tree while growing. This includes sodium. When the ashes are added to the brew, it forces the reaction to the right and produces more soap.
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