If the silver jewelry you wear turns black, does it mean that your body is detoxifying? The truth is...

"When you wear a silver bracelet and it turns black, it absorbs toxins from your body"

Many people have seen some TV dramas about testing poison with silver needles and believe that wearing a silver bracelet can also be used to absorb toxins from the body. Some even say that if the silver bracelet turns black, it means that the toxins in the body have been discharged.

Rumor analysis: Not true.

The blackening of silver bracelets is actually due to the long-term exposure of silver to the air, which causes an oxidation reaction to generate black silver oxide. In addition, the sweat and other secretions secreted by the human body can react with silver on the one hand, and accelerate the oxidation rate of silver on the other hand, generating black silver rust (Ag2O, Ag2S).

In ancient costume dramas, we often see such plots: before eating, the protagonist will take out a silver needle to test the food for poison. If the silver needle turns black, it proves that someone has poisoned it. Some people even use silver chopsticks to eat directly, just to avoid poisoning in all aspects.

Image source: Stills from "The Legend of Zhen Huan" Many people are inspired by this kind of plot and believe that wearing silver bracelets can also be used to absorb toxins from the body. If the silver bracelet turns black, it means that the toxins in the body have been discharged. But in fact, whether it is the blackening of the silver needle when testing poison or the blackening of silver jewelry when we wear it, it has nothing to do with toxins.

Where did the rumor about Silver Bracelet taking drugs come from?

Let's first talk about what the so-called silver needle test for poison is. In Chinese history, there is indeed a practice of silver needle testing for poison. For example, Song Ci, a famous forensic doctor in the Song Dynasty, recorded the famous "Huai'an Strange Case" in "Xiyuan Jilu", and the method of solving the case was "silver needle testing for poison". The poison that the ancients could test with silver needles was mainly arsenic. Arsenic and the famous Crane's Red were commonly used poisons in ancient times, and the main ingredients of these two poisons are actually arsenic trioxide. In ancient times, the ancients mainly extracted arsenic from natural arsenic-containing minerals, such as arsenopyrite, realgar ore, and orpiment. These minerals are also called arsenic stone and realgar. But these minerals are not composed of arsenic alone. Because arsenic is unstable, it appears in nature in the form of compounds formed with other elements. Sulfur and arsenic are a pair of model cps, and they appear in pairs in many minerals. For example, the realgar that Xu Xian gave to White Snake to drink is tetraarsenic tetrasulfide; and the corresponding orpiment is arsenic trisulfide.

Image source: Stills from The Legend of White Snake

In order to separate them, the ancients usually used heating methods. The preparation method at that time was recorded in "The Exploitation of the Works of Nature": crush the arsenic stone and heat it in an earthen kiln. A large pot was turned upside down on the chimney above the kiln. After a period of time, arsenic trioxide would form a layer of crystals on the pot. Because it looked like a layer of white frost, people gave it the name arsenic trioxide.

Of course, such a simple and rough purification process also determines that there will inevitably be a lot of sulfides remaining in the finished arsenic. And it is these sulfurs that are tested when the silver needle is tested for poison. After silver and sulfur come into contact, a chemical reaction can occur without heating to generate black silver sulfide, and the silver needle will naturally turn black. Therefore, the ancients used silver needles to test poison, and they could indeed test out arsenic in the food. But if it is other poisons that do not contain sulfur, there is no way. Therefore, the silver needle test for poison is purely a mistake in the era of underdeveloped technology. If we use silver needles to test arsenic now, we will find that there is no change at all. This is because modern purification techniques can completely remove the sulfides in arsenic, and pure arsenic trioxide will not react with silver. Since silver itself does not have the effect of "testing poison", it is naturally nonsense to use silver bracelets to absorb toxins in the human body. But it is also an indisputable fact that silver bracelets that have been worn for a long time turn black. What's going on?

The silver bracelet turns black, it is actually oxidized

When we visit a museum, we often see some ancient silver wares unearthed from the ground, which are usually silver with black in color. The black surface of these silver wares is mainly silver oxide formed by the oxidation of silver.

Although the physical and chemical properties of silver are relatively stable, if it is left in the air for a long time, silver will still slowly oxidize to form silver oxide. This is the real reason why the silver jewelry we wear turns black - it is not that silver absorbs toxins from our body, but that it reacts with oxygen in the air to form silver oxide.

However, you may want to ask at this point - the ancient silverware was left in the air for hundreds of years before it turned black, so why did the silver bracelets we wear turn black after a short time? Of course, it is because we "accelerated" the oxidation of silver without knowing it. First of all, our human body also produces sulfides. In our body secretions, such as sweat, there will be some sulfides, and silver has a strong affinity with sulfur, so the speed at which silver turns black will naturally accelerate. In addition to promoting the oxidation of silver, sulfur will also form silver sulfide with silver, which is also black. Sulfide is a normal component of sweat, but the content is usually relatively low. However, if we eat more sulfur-containing foods for a period of time, such as onions, garlic, onions, etc., then the sulfur in the sweat will increase.

Copyrighted stock images, no reproduction is authorized

In addition, various chemical substances we come into contact with when wearing silver jewelry may also accelerate the oxidation process of silver. For example, some acidic substances may also accelerate the oxidation of silver. The environment will also affect the discoloration process of silver. In a high temperature and high humidity environment, or in areas with high sulfide content in the air or heavy air pollution, the oxidation speed of silver jewelry will also be faster.

If you want your silver jewelry to be white, just do this

In daily wear, it is difficult to avoid silver jewelry from oxidizing and turning black. So how can we make the silver jewelry that has turned black turn back to silvery white?

Copyrighted stock images, no reproduction is authorized

A relatively simple and crude method is to polish and grind off the blackened oxide layer on the surface. For example, the trick of using toothpaste to rub silver jewelry to make it white is actually to use the small particles in the toothpaste to complete the polishing process. When we buy silver jewelry, the silver polishing paper that is often given is actually based on a similar principle. Remove the blackened part of the surface to expose the unoxidized silver inside, and it will naturally turn white. However, it is a bit painful to throw away the discolored silver in such a simple and crude way. We can also use the reduction method to change the oxidized/sulfurized silver back. The main effective ingredient in the common silver washing water on the market is actually the reducing agent. This method can prevent the silver jewelry from losing weight after washing, and it will not lose weight after cleaning. If you think it is troublesome to clean silver jewelry every once in a while, there are actually many silver jewelry protective agents on the market. Their principle is to form a transparent but airtight protective layer on the surface of silver to prevent silver from contacting our sweat and external air, just like putting a protective coat on silver, which naturally prevents silver jewelry from turning black. Choosing silver jewelry that has undergone this anti-oxidation treatment, or purchasing products that have undergone anti-oxidation treatment, can also prevent the silver jewelry from oxidizing too quickly.

Looking in the mirror of rumors

If we observe carefully, we will find that silver will turn black as it oxidizes even if it does not come into contact with the human body. If we think about it a little more, we will understand that it is nonsense to say that silver turns black to detoxify the body. In the face of some rumors from life, we can judge them based on our daily observations and experiences, so that many rumors will be broken without any attack.

Review丨Sun Mingxuan, Professor of Shanghai University of Engineering Science

Gu Miaofei, Ph.D. in Chemical Engineering, Editor and Deputy Editor of Science Pictorial