"When You're Hungry, the Periodic Table" is the second periodic table story by author Kwak Jae-sik in three years.
Following the introduction of twenty elements with atomic numbers 1 to 20 in the previous work, “When Going on Vacation, the Periodic Table,” “When Going Out, the Periodic Table” contains stories of twenty elements with atomic numbers 21 to 40.
However, for many people, the names of elements 1 through 20 are familiar because they were taught to memorize them in school, but for elements 21 and above, most people are unfamiliar with the names because they haven't had many opportunities to look at them.
So, the author tells the story by relating all the elements to the food we eat, so that we can feel a little closer to the unfamiliar elements.


As can be guessed from the subtitle, ‘A Biography of Metals Related to Food and Living,’ many of the elements covered this time are metals.
When we think of metal, we immediately think of sharp, hard iron, but what does that have to do with the food we eat? Just as doctors often recommend eating more iron, and zinc-containing supplements are sold commercially, some metallic elements are actually important components of food.
So the author tells a long story about why we eat it and what happens in our bodies when we eat it.
There are also elements that are essential for the tools and equipment used when making food, and there are also stories about how certain foods are sometimes damaged by certain elements.
The author, a doctor of engineering and novelist, explores not only scientific knowledge but also history, current affairs, economics, and popular culture to create a captivating story about the elements.
As we follow the story, we come to realize that various elements are involved in our lives in various ways.

Let's think about continuously extracting sulfur dioxide from smoke.
Then, pollutants that have no place to be disposed of will gradually accumulate.
What can we do with all this sulfur dioxide? In this case, we can create sulfuric acid by adding vanadium pentoxide to the collected sulfur dioxide and causing a chemical reaction.
The sulfuric acid or sulfur dioxide component that is created in this way is removed, and the remaining substance can be sold for money to where it is needed.
In other words, sulfur dioxide, which was just a nuisance and cost that had to be forcibly removed to prevent air pollution, can be converted into a valuable product using vanadium pentoxide and generate profits.


I believe that it is just as important to find ways to make environmental protection actions beneficial as it is to emphasize a love for the Earth and a sense of duty to do good deeds to prevent environmental pollution.
If you link environmental protection activities to benefits, like the technology that uses vanadium pentoxide, then people will step forward and do it for the benefit of their own accord, without the government having to force or crack down on them.
I call this method of protecting the environment while also gaining profit the “killing both the pheasant and the eggs,” and vanadium is playing an important role that can be put forward as a representative example of this method.
Vanadium played a significant role in helping us escape the fear of acid rain.

--- From "23 Vanadium: Savoring the Taste of Living Water"

The reason the sun shines so brightly is because nuclear fusion occurs within the sun, transforming the element hydrogen into helium.
As heat is generated during the nuclear fusion process, the surrounding area becomes hotter.
The surrounding pressure also increases.
So once nuclear fusion occurs, the heat causes more nuclear fusion to occur in the surrounding area.
If nuclear fusion occurs nearby, that much heat will be generated there.
Then, because of that, nuclear fusion occurs again around it.
In this way, once nuclear fusion occurs, it can continue continuously.
In stars, this goes on for hundreds of millions, even billions of years.
As one element combines with another, new elements are continuously created.

But there is one strange stumbling block here.
That's iron.
When elements combine to form new elements and iron is created, things change from then on.
Even if you try to force nuclear fusion by adding other elements to iron, it does not release as much heat as when nuclear fusion of other elements occurs.
On the contrary, it makes the surroundings colder.
Therefore, once iron is created, the heat generated by nuclear fusion can no longer continue to cause further nuclear fusion.
In other words, iron is the last substance created in the process of stars creating various elements through nuclear fusion and emitting light, and it is the substance that breaks the link of heat.
You could say that the ashes of a star are iron.

--- From "26 Iron: Waiting for the Dodari Mugwort Soup"

However, this does not mean that copper is useless in the human body.
There are several enzymes in the body that use copper, although in very small amounts.
Therefore, if you do not eat any food containing copper, something will definitely happen to your body, and if you are so deficient in copper that you may need to supplement copper.
However, the human body can usually absorb enough copper to meet its needs, even with just a small amount found in many foods.
Eating a certain amount of seafood that is high in copper, such as soy sauce marinated crab, can help you more easily meet your body's needs.

However, if you drink wastewater from a copper factory, too much copper will accumulate in your body and you will become sick.
In particular, it is known that if a lot of copper accumulates in the liver, it cannot function properly and causes illness throughout the body.
A case that occasionally appears in Koreans is Wilson's disease.
Although it is a rare disease, it is said that among liver diseases, there are more cases in Koreans than in other countries, and that about one in ten thousand Koreans has this disease.
Wilson's disease is a genetic disorder that occurs when a person's body cannot properly process copper.
When a person consumes copper through food, etc., the body uses as much as it needs and excretes the rest as waste. However, if copper accumulates in the wrong places in the body due to an abnormality in the body's constitution, it can lead to Wilson's disease.

--- From "29 Copper: Cleaning the Crab"

What does "bromide" really mean? Originally, "bromide" was an English word meaning a chemical substance made from bromine.
This name is often given to substances that are made by a chemical reaction called oxidation using bromine.
For example, hydrogen bromide refers to an acidic substance made using hydrogen and bromine.
After knowing this much, you might start to think something is strange.
When you buy a magazine that claims to offer bromide, don't you get a vial filled with a chemical made from bromine? Why did this term come to mean a large photo of a celebrity? It's because bromine's chemical properties were exploited to create a substance that reacts well with light, which was then used to create photographs.
In particular, silver bromide, made from silver and bromine, was a substance that was widely used in the past when making photographs.


Nowadays, most people take pictures with smartphone cameras or digital cameras that use semiconductors and can view them immediately on the screen.
However, in the past, you could only see a photograph by recording it on photographic film and then going through a process called development, which involves printing the photograph on the film onto paper.
At this time, various chemical reactions had to occur properly to produce clean and good-looking pictures.
As a result, some photographers began to boast about the special, high-performance bromide materials they used to make high-quality photographs.
Later on, the word bromide itself was changed to mean a high-quality photograph made using such good materials.

--- From "35 Bromine: Boiling Fish Cake Soup"

As the temperature approached 1,200°C, zirconium began to exhibit an unusual property of reacting with water to produce hydrogen.
Currently, there is no need for a reaction to extract hydrogen from water, but when the high temperature condition is met, zirconium starts a hydrogen-producing reaction that no one wants.
The water and steam inside the reactor began to decompose into oxygen and hydrogen because of the zirconium.
In situations where fuel is needed, hydrogen is a clean substance that can save the planet, but when hydrogen is gushing out inside a nuclear reactor where it is not needed at all, it becomes a headache.
Even the zirconium releases heat as it extracts hydrogen from the water, further increasing the temperature inside the reactor.

Zirconium, which was normally placed there as a defensive plate for safety, ended up producing a lot of hydrogen as a tinder in this emergency situation.
Saying that hydrogen is a good fuel basically means that it is a substance that catches fire easily.
Eventually, the hydrogen ignited and caused an explosion.
The nuclear power plant's equipment was destroyed and everything began to break down uncontrollably.
After a while, radioactive materials inside the reactor began to leak out into the surrounding area.
The area around the Fukushima nuclear power plant became uninhabitable for ordinary people, and radioactive materials were mixed into the water in enormous quantities, causing mountains of contaminated water to pile up.

After the Fukushima accident, scientists studying nuclear power technology in many countries around the world, including Korea, began to study more closely than ever before what to do if hydrogen starts to form inside a nuclear reactor.
Cars that run on water, clean energy hydrogen, and mysterious catalyst technologies are not far from such terrifying accidents.
Many of the principles of science are both good and evil, and their implications depend on how people use them.

--- From "40 Zirconium: Opening a Bag of Cookies"