- Why we do not keep curd and sour substances in Brass and copper container
Curd and sour substances are acidic in nature viz. The lactic acid in curd, citric acid in lemon. Acidic substances react with copper and form insoluble metal salts. This complex releases itself into the food. So, to avoid food contamination with copper we do not use curd, sour substances like pickles, vinegar etc in a copper vessel.
You must have seen the greenish-black appearance on copper idols. Water and atmospheric air form nitric acid. Nitric acid form salts with copper which ale black and green in appearance.
Next: Why a reaction of a meta with acid liberates gases. And how do we detect them?