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Why are some of the ashes from a campfire black, while other parts of the ashes are white?

Answer:

The black parts are only partially burned. The black color is due to unburned carbon from the wood. The white part is the mineral ash, nutrients that the tree roots took in from the soil. It contains quite a bit of potassium, which is why wood ashes are used in soap making. With water, the ashes form potassium hydroxide, an alkaline substance that plays a role in changing fats into soap.