Why is the white tin button missing?

On June 23rd, 1812, under the bright sunshine in early summer, Napoleon led his invincible army across the Neman River and set foot on Russian soil. Despite the tenacious resistance of the Russians, the French army still won a series of victories and advanced into the hinterland of Russia, capturing Smolensk in August and Moscow in September.

just as Napoleon was planning the next stage of military action with great satisfaction, the winter in Russia came early. A cold current from Siberia swept over the northern part of Russia, and the biting cold wind roared into every corner. There was heavy snow in the sky, and the temperature dropped sharply, ℃, -1℃,-2℃ ... < P > French soldiers from temperate regions had never encountered such a situation, and all of them were frozen to death. Napoleon had to order the withdrawal. On November 29th, the army retreated to the Berezin River. The large troops crossed the bridge and continued to retreat to the west. A guard force stayed, and they were ordered to blow up the bridge tomorrow morning after the stragglers crossed the bridge to stop the chasing Russian troops.

that night, another cold current hit, and the red alcohol column on the thermometer dropped to -38℃. At last it was dawn, and the soldiers who woke up stood up to exercise and tidy up their clothes. Suddenly, everyone found that the white tin button on the military coat was missing. What was even more embarrassing was that everyone had to hold the military trousers in their hands, because the white tin button on it was also missing.

Embarrassment is a trivial matter. What's terrible is that the Russian army may catch up at any time. How can we fight like this? The leading officer immediately gave an urgent order: immediately peel off the shirt from the dead body, tear it into strips, tie the trousers and tie the coat ...

The French couldn't find out what caused the embarrassment on the banks of the Na River in Berezin, so they had to record it in the military history and leave it to future generations to ponder.

in less than 5 years, such a miracle happened again in Russia.

In p>1867, winter arrived in northern Russia earlier, and the temperature dropped below -3℃ in October. St. Petersburg military supplies warehouse received an urgent notice and immediately sent the woolen coat that had just been put into the warehouse to the troops. When the administrator took the military coat out of the box from the warehouse, a cold sweat broke out on the quartermaster's head-all the white tin buttons on the military coat were gone, leaving only some gray powder where the buttons were nailed.

what's going on? Tin is not a very valuable metal, and it is inconceivable that anyone would steal with evil intentions. So, is someone deliberately making trouble?

"Someone is really making trouble!" Before long, the chemist finally found out the reason: it was a prank in the cold weather.

It turns out that the solid of tin will present three different situations with the change of temperature. The tin at room temperature is bright, which we call "white tin". It has excellent ductility and can be pressed into very thin tin sheets. People call it tin foil.

if white tin is heated to above 161℃, it will become very brittle, and it will break into powder when it is knocked on. Therefore, people call it "brittle tin". If brittle tin continues to be heated to 231.8℃, it will melt into liquid state. This melting point of tin is relatively low among metals.

tin can't stand heat or cold. When the temperature is lower than -13.2℃, the crystal lattice of white tin changes. At this time, it is not only dark in color, but also loses the characteristics of metal, and the internal stress at the junction of each lattice causes the crystal to break and turn into gray powder. This powdery tin is called "gray tin".

Although this transformation started at -13.2℃, the trend of transformation was not great. When the temperature drops to -33℃, this change will happen quickly. A good tin button will turn into a pinch of coal ash powder in one night. If the temperature is lower, such as -5℃, we can even see that white tin will disintegrate and collapse rapidly.

This change of tin is called "tin plague". Strangely, this change is still "contagious". If you contact a tin container with a "tin epidemic" with a "healthy" tin container, the previously intact tin container will soon be infected with an "epidemic", just like the plague of people and animals spreading. This is because the existence of a small amount of gray tin can greatly promote the process of transforming from white tin to gray tin.

after people understand this truth, they can use tin selectively. At least, the soldiers in the cold areas later wore no more buttons made of tin. In this way, the wonders like St. Petersburg and the embarrassment on the banks of the Berezin River will not appear again.