The principle of silver needle blackening in fortune telling

Why does the silver needle turn black?

The chemical principle of ancient "silver needle testing poison";

When people talked about highly toxic substances in ancient times, they basically referred to arsenic. Arsenic has become a common poison in ancient times, mainly because it is relatively simple to obtain, and its raw materials are very rich in ores. Arsenic can be extracted from ores by simple processes.

The crude refining methods of the ancients made the purity of arsenic not high. Even white arsenic still contains a lot of sulfur or sulfide, which will react chemically with silver to produce black silver sulfide. Therefore, once the silver needle comes into contact with arsenic, the surface will turn black, so it can be judged whether the food contains toxicity.

Silver can't test poison, but it can disinfect;

As long as every liter of water contains one milligram of 50 million silver ions, most bacteria in the water can be killed. Its principle is that silver can form positively charged ions in water, adsorb bacteria in water and gradually enter bacteria, so that its catalyst-anchoring system is deactivated, and bacteria lose their metabolic ability and die. Therefore, it is good to use silver to make dishes and chopsticks in daily life.

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