Question

why should copper and other substance not be kept in brass and copper vessels

Answer 1

Copper and other substance can be kept in brass and copper vessels but the only thing is that the acidic things cannot be put or store in a copper or brass substance because acid react with brass and copper

Answer 2

$<i> Curd and other sour substances contain acids. Therefore, when they are kept in brass and copper vessels, the metal reacts with the acid to liberate hydrogen gas and harmful products, thereby spoiling the food.$