Dry distillation
Dry distillation is the heating of solid materials to produce liquid or gaseous products. As the products distill off, they are condensed and collected. This method usually requires higher temperatures than liquid distillation. The method can be used to obtain liquid fuels from coal and wood. It can also be used to break down mineral salts such as sulphates, in this case producing sulphur dioxide/trioxide gas which can be dissolved in water to obtain sulphuric acid. This is how sulphuric acid was first produced.
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