But in the professional...or rather university field, this statement is actually wrong.

Because in the high school realm, the discharge order of hydroxide ions in water comes before oxyanions, so oxyanions cannot discharge.

However, in reality, due to the existence of overpotential, a side reaction that generates H2S2O8 will occur, exceeding the standard electrode potential of 2.01V, forming an overpotential situation.

Therefore, the electrolysis of dilute sulfuric acid is actually somewhat different from that of water.

Returning to the original place.

With the input of electrical energy, the sodium chloride in cup A was quickly electrolyzed.

Hydrogen gas is generated at the cathode.

Chlorine gas is generated at the anode.

These generated gases escaped and were collected by a glass conduit into a container placed in the dark, out of sight.

Chlorine gas at the bottom, hydrogen gas at the top.

When ignited, white mist forms at the mouth of the bottle. (Not recommended to try it, it's prone to explosion)

This white mist was then led by a glass tube into another water-filled container, dissolving in the water.

As a result.

A high-concentration hydrochloric acid was prepared.

Reading up to here, some students might ask:

No, isn't it enough to directly dissolve chlorine gas in water to get hydrochloric acid? Why go through all this trouble?

The reason is simple:

Chlorine gas generated by electrolysis can also be dissolved in water to obtain hydrochloric acid, but this reaction actually produces a chlorine-water mixed solution.

Besides hydrochloric acid, it also contains Cl2, H2O, HClO, H+, ClO-, Cl-, OH- and various other ions.

Not only is the reaction reversible, but the concentration of hydrochloric acid is also very low.

The effectiveness is much worse than the hydrochloric acid prepared by Xu Yun.

Of course.

Again, a reminder not to easily react chlorine gas with hydrogen, or explosions can easily occur.

Returning sight to the original place.

After the operation was completed, Xu Yun filled the hydrochloric acid into different containers.

Looking at Old Su beside him, he did not rush to the next step, but instead asked Old Su:

"Master, can you find someone to catch some cockroaches?"

"Cockroaches? Why do you need those?"

"I have my own use for them."

Old Su had seen a lot of Xu Yun's strange operations today, so he did not question further. He glanced at Mr. Xie beside him and instructed:

"First Year, quickly find someone to catch some cockroaches."

Mr. Xie nodded and turned to arrange for manpower.

As mentioned a long time ago.

Cockroaches have existed on Earth for hundreds of millions of years, their history is older than that of dinosaurs, and can even be considered one of the longest-existing creatures on Earth.

Coupled with the fact that the hygiene standards during the Song Dynasty were much lower than those of later generations, and it was summer, cockroaches were naturally seen everywhere.

Thus, not long after, Mr. Xie returned holding a glass bottle:

"Master, Brother Wang, the cockroaches have been caught."

Xu Yun took the glass bottle and immediately smiled.

Good fellows.

Again, it's the American cockroach, the old standby.

At this moment, these American cockroaches were thrashing about in the bottle, evidently Old Su's family had good food.

Then Xu Yun laid the glass bottle flat, signaling Old Su to step aside a bit.

He opened the bottle, picked up hydrochloric acid and poured it in.

Normally, hydrochloric acid is very corrosive to living organisms, but killing them is difficult.

However, cockroaches are quite special:

Their surface contains a protein called tiec, and hydrochloric acid ranks first among acids in terms of corrosiveness and destructiveness to this protein, with a significant lead over the second.

Therefore, hydrochloric acid is also a very effective cockroach extermination substance.

Pa la—

As hydrochloric acid was poured.

The cockroaches first panicked and crawled around the bottle.

But soon, their surface was corroded by hydrochloric acid, creating breaks.

In just a few minutes, these unlucky fellows finally.....

Suffocated and died.

Annihilated Family American Cockroach.JPG.

Seeing this situation.

Old Su's pupils suddenly shrank, exclaiming in horror:

"How...how is this possible? Is salt actually poisonous?"

Seeing this, Xu Yun smiled slightly, saying nothing.

Old Su's reaction was within his expectations, or to put it plainly, it was also one of his purposes:

In the ancient times, with near-zero microscopic cognition, nothing was more impactful than extracting 'highly toxic' substances from the table salt consumed every day.

Once he completed what he was doing, Old Su would inevitably ask him some questions.

And without exception, these questions would be relevant to the microscopic field.

Having such an example happening right before their eyes makes some words obviously more convincing.

Then Xu Yun collected the prepared hydrochloric acid and picked up another item Old Xu had prepared:

Poisonous Heavy Stone.

Poisonous Heavy Stone is a barium-containing ore, often used in later industrial processes for acid-leaching to prepare barium chloride.

Xu Yun took the ground-up Poisonous Heavy Stone, washed it clean, picked up a small spoon, and added it to the hydrochloric acid solution.

Half an hour later.

A mixed solution had been successfully prepared.

Xu Yun then started adding sodium hydroxide to it—one of the products of the previous electrolysis, although it contained other cations, they were already the target products, so they wouldn't affect the reaction process at all.

Wanting every link to be seamlessly connected took a lot of Xu Yun's effort.

As everyone knows.

In the Poisonous Heavy Stone solution, the pH for complete precipitation of Fe3+ is 3.2, for Mg2+ is 11.1, and for Ca2+ is 13.9. (Refer to paper 10.16283/j.cnki.hgkwyjg.1996.06.014)

Thus, Xu Yun didn't need to care about the real-time data of pH value, just observing the precipitous changes in the reaction process was enough.

Another hour passed.

After dropwise addition of sodium hydroxide and filtration.

A standard barium chloride solution was formed.

At this step, the rest is simple, which is.....

The purification of crude salt, a junior high school concept.

First, add excess BaCl2 to remove sulfate ions.

The reaction formula is BaCl2+Na2SO4=BaSO4↓+2NaCl.

Then, add excess NaOH to remove magnesium ions:

MgCl2+2NaOH=Mg(OH)2↓+2NaCl

The third step is to add soda, which is sodium carbonate.

This stuff is omnipresent in the glass-making industry, and its purpose is to remove calcium ions and barium ions in BaCl2.

Finally, add HCl to remove excess NaOH, Na2CO3—this process, if conditions permit, can be observed with pH paper for the amount of hydrochloric acid, if not, just pour and evaporate the excess.

Then, another hour passed.

A large cluster of precipitated sodium chloride crystals came out.

Xu Yun measured the dose, dissolved them in water.

Just like that.

A standard concentration saline officially arrived in the year 1100.

On the other side.

Watching Xu Yun, who was engrossed in configuring the garlic injection, Old Su finally couldn't hold back:

"Xiaowang, why does the salt undergo this kind of treatment and become such a highly toxic substance?"

......

Note:

I don't know if anyone would ask why making salt needs to be so complicated. Here's the thing, it wasn't just to make salt....

In order to fit the later plot, you wouldn't know how exhausted I was writing this.....ahem, disturbing my friends.....

Begging for a monthly pass, as there are additional activities for monthly pass...

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