Question

why should curd and sour substance not kept in brass and copper vessel.

Answer 1

Curd and sour substances contain weak organic acids in them. So when kept in metal containers like brass and copper can react with the metals and form poisonous salts which can be harmful for the health of an individualm

Answer 2

curd and other sour substance contain acid which can react with the metal of brass and copper vessel to form toxic metal compound which can cause food poisoning and damage our health.