In ancient books, about silver needle testing poison.

In many costume dramas, you will see silver needles inserted in food to test whether they are poisonous or not. If the silver needle does not change color, it is non-toxic. On the contrary, if the silver needle turns black, it means that the food is poisonous.

There is also a record of silver needle autopsy in the Collection of Injustice in Song Dynasty, so is it correct to test poison with silver needle?

First of all, it is certain that there is a scientific basis for testing poison with silver needles, because silver needles contain silver and some toxic substances contain sulfur. When these two elements meet, there will be obvious chemical reaction to produce silver sulfide, which will lead to the discoloration of silver needle, which also shows that silver needle can use sulfur to detect toxic substances.

In ancient times, the technology of producing arsenic (As2O3) was immature, which generally led to sulfur slag or sulfide impurities in arsenic. Arsenic was put into the food of ancient silver needles, and silver and sulfur met, which led to the discoloration of silver needles.

In fact, the silver needle will not change color when it meets toxic substances, but will turn black when it meets sulfur. Similarly, if you test the egg's Huang with a silver needle, it can also change color. Is it true that egg yolk is also poisonous? Of course not, just because the egg yolk contains sulfur. Officially, because of this element, the egg yolk will turn black when inserted into the silver needle.

In addition, many poisons are undetectable by silver needles, such as nitrite, potassium cyanide and sodium cyanide. Because it does not contain sulfur and cannot react with silver, the silver needle will not turn black when it meets these substances.

With the development of science and technology, pure arsenic can be extracted, which means that arsenic does not contain sulfur, so the silver needle will not change color no matter how it is tested.

The older generation thinks that wearing silver ornaments can detoxify. They found that wearing silver jewelry for a long time would change color, thinking that it would absorb human toxins. This idea is wrong. The truth is that wearing silver jewelry for a long time will have close contact with human sweat. There will be trace sulfur in human sweat, which will change color after a long time. Oxygen in the air will also oxidize silver jewelry, and silver jewelry will also change color after a long time.