Question

why should curd and sour substances not be kept in brass and copper vessels​

Answer 1

Curd and sour substances contain acid. ... sour substances are cidic in nature,i.e, they have acids in them. So, when they are kept in brass or copper vessels, they react with them and form poisonous or better to say toxic elements which may prove harmful for human body. So they are not kept in metal containers.

Answer 2

Curd and sour substances contain acids. Therefore, if we keep such food substances in brass and copper vessels, they will react with the metal to form poisonous metal compounds and liberate hydrogen gas thereby causing food poisoning and corrosion of the vessels.