Question: What is the chemical formula of the kind of ash of which Middlewich Folk and Boat Festival celebrates the raw materials needed for the manufacturing?
Sentence (from "Middlewich Folk and Boat Festival"): The festival builds on the town's industrial heritage in which canal boats were used to move coal and other raw materials in the town for the production of salt, and then move the salt out of town, either for use directly, or as a raw material in the manufacture of chemicals such as chlorine and soda ash.
Relevant evidence: Yes