A small update in my research:
1: oxalic acid is commonly used to leach iron out of clay - the process is very simple and can be done during the last step of purifying raw clay
2: hydrogen chloride is very expensive and dangerous - for someone like myself who is not very knowledgeable in chemistry, it would be a very bad idea if I attempted to produce this gas myself. From what I have been reading, I may be able to achieve a similar effect by using 20% hydrogen peroxide in the hydrochloric acid solution containing the aluminum chloride .
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