The second question, about the blackening of silver necklaces, is widely circulated because silver can take drugs. People wear silver necklaces for a period of time because there are more endotoxin in human body, and silver necklaces will turn black after absorbing human toxins. Actually, this is a misunderstanding. The blackening of silver necklaces has nothing to do with health. The real reason why silver necklaces turn black is that air and human sweat often contain oxides such as sulfur, and silverware is easy to oxidize when it comes into contact with these oxides. Over time, there will be grayish-brown silver oxide on the surface of silverware, which will make silver ornaments appear black.