Question

Why should curd and sour substances not be kept in brass and copper vessels?

Answer 1

we know that curd and other sour substances contain acids in them.when acids react with metals,they form metal compounds which are poisonous and also liberate hydrogen gas.So,if we keep such sour substances in metal containers like brass and copper,it will result in food poisoning and corrosion of vessels

Answer 2

Because curd and sour substances are acidic in nature and when we will kept this acid in  brass and copper then it will react with brass and copper and will form salt and hydrogen gas