Is there a scientific basis for silver needles in film and television dramas to turn black when they

There is a certain scientific basis, the poison used in ancient times is mostly a substance with a certain element (mercury or arsenic...) It can react with silver to form a black compound, and the silver needle becomes black, and I also saw it before, and now I have forgotten it...

Silver needles will produce a kind of silver sulfide when it encounters sulfur or sulfide, and arsenic in ancient times, because of backward production technology, will contain impurities of sulfur and sulfide. When the sulfur contained in it comes into contact with silver, a chemical reaction occurs, causing a black layer of silver sulfide to be formed on the surface of the silver needle.

In ancient times, the silver needle test actually refers to the sulfur or sulfide in the test poison. In modern times, the technology for producing arsenic is much more advanced than in ancient times, and the refining is pure, generally not mixed with sulfur and sulfides. So under normal conditions, the silver needle does not react with arsenic and does not turn black.

The chemical principle of the ancients' "silver needle test poison":In ancient times, when people talked about highly toxic things, they basically referred to arsenic, and the reason why it became a poison commonly used by the ancients was mainly because the acquisition of arsenic was relatively simple, and its raw materials existed in a large number of ores, and only a simple process was needed to extract arsenic from ores.

The rough refining method of the ancients made the purity of arsenic not high, even if it was white arsenic, it still contained a lot of sulfur or sulfide, and the sulfide would undergo a chemical reaction when it encountered silver to produce black silver sulfide. Therefore, once the silver needle touches the arsenic, the surface will turn black, and it can be judged whether the food contains toxicity.

Silver cannot be tested for poison, but it can be disinfectedAs little as 1 milligram of silver ions per liter of water can kill most bacteria in water. The principle is that silver can form positively charged ions in water, which can adsorb bacteria in water and gradually enter the bacteria, so that its catalyst-amidium system is closed and inactivated, so that the bacteria lose their metabolic ability and die.

Therefore, it is still beneficial to use silver as bowls and chopsticks in daily life.

The above content reference: Encyclopedia - Silver Needle.

In fact, the silver needle test does not react with the poison, but with the sulfide in the poison. Realgar (AS2S2) and orpiment (AS2S3), after they encounter the silver needle, they will form a black oxide on the surface of the silver needle - silver sulfide (AG2S), which is based on this principle, so there is a silver needle test poison test.

The world is made up of matter, and there are two main forms of change: chemical change and physical change.

Different from particle physics and nuclear physics, which study smaller scales, the material structure of atoms, molecules, and ions (clusters) studied in chemistry interact with chemical bonds and intermolecular forces, and the scale in which they are located is the closest to the macrocosm in the microscopic world, so their natural laws are also most closely related to the physical and chemical properties of substances and materials in the macrocosm of human existence.