Chapter 123 The Song Dynasty also wants to kill cockroaches
In the 21st century.
Compared with hand-made generators, the concept of electrolysis may be more widely spread.
Especially the electrolysis of saturated salt water, this is an extremely basic chemical practical reaction.
In an electrolysis experiment, a reduction reaction occurs at the cathode, at which time it receives electrons.
The anode will undergo an oxidation reaction and lose electrons.
At the same time, after the electrolysis reaction occurs, some anoxic acid salts of active metals will generate alkali at the cathode.
Oxylate salts of inactive metals will generate acids at the anode.
In addition, after the electrolysis reaction occurs, the cathode will also produce solid and reducing gases.
As for the choice of cathode and anode...
A common operation for electrolyzing saturated brine is to use copper as the cathode and carbon rods as the anode.
Of course.
If the conditions are normal, two carbon rods actually have no effect.
However, there is a special feature of electrolyzed saturated salt water, that is, chlorine gas easily reacts with sodium hydroxide.
That is, 2NaOH Cl2=NaCl NaClO H2O.
Therefore, in modern industry, porous and permeable separators are generally used to separate the anode chamber and the cathode chamber so that the two do not come into contact.
However, the current Song Dynasty obviously cannot do this kind of technology, so Xu Yun is considering...
Salt Bridge.
Inside the courtyard.
After preparing the generator materials, Xu Yun turned around and asked Lao Su:
"Master, I wonder where is the white crystal block I bought from the sour plum shop?"
Lao Su pointed to a package on the left and replied:
"That package is, Xiao Wang. If I hadn't judged correctly, this thing should be saltpeter?"
Xu Yun walked over and opened the package, examined it carefully, and affirmed:
"Yes, it is indeed saltpeter.
I heard that the old man spoke with a Hexi accent, so I guess the saltpeter was transported from Hexi."
Old Su nodded thoughtfully and said:
"I see. No wonder he came back in the first year and told me that the couple thought he was a spy sent by his colleagues at first, and even clamored to report him to the official.
Later, he had no choice but to reveal his identity card to the county government, and also invited a government official on the street to testify, and then the other party was willing to sell him some crystal nuggets, and the price was not low."
Xu Yun shook the saltpeter in his hand with great satisfaction and said:
"It's normal for saltpeter of such quality to be expensive. It can save a lot of trouble."
When he saw iced sour plum juice in the sour plum shop, Xu Yun thought about two possibilities for the old man to make ice.
One is the ice cellar.
The second is saltpeter.
Among them, the possibility of ice cellars is not very high. After all, the production cost of ice cellars in this era is not low. Only people in large courtyards can build ice cellars to store ice.
Therefore, although Xu Yun was not sure that the opponent must have saltpeter in his hand, he was almost seventy percent certain.
With saltpeter, potassium nitrate can be prepared.
Students who didn’t fail biology should remember it.
Potassium nitrate is a common salt bridge.
The so-called salt bridge refers to an electrolyte that can communicate between two beakers, allowing anions and cations to move freely from the cathode to the anode.
With the potassium nitrate salt bridge, it can prevent the chlorine gas generated by electrolysis of salt water from reacting with sodium hydroxide in the electrolytic cell to the greatest extent, thus promoting the production of chlorine gas.
As for the preparation of potassium nitrate, it is also very simple:
First dissolve the saltpeter in water and then remove the sediment.
After heating, evaporation and concentration, KNO3 crystals can be obtained after cooling.
Potassium nitrate crystals have extremely strong solubility, so these crystals are redissolved in water, and a salt bridge is created.
After all the preparatory work is completed.
Xu Yun put the refined salt prepared by Mr. Xie into the water and started stirring with a glass rod.
soon.
The solution started to become a little turbid.
Xu Yun looked at Lao Su:
"Sir, could you please bring me some gauze?"
Although Lao Su didn't quite understand his intention to operate on Xu Yun, he still handed him a funnel covered with gauze.
Pattering——
Xu Yun poured the turbid liquid down.
As the gauze blocks, some insoluble impurities are filtered out.
Then he divided the filtered solution into two large cups, let's call them cup A and cup B.
Um.
It's just a cup, without the word "hood".
Then he first connected the A cup to the electrolysis equipment - the electrolysis equipment was not very different from the equipment used in later generations to electrolyze saturated salt water. The anode had a conduit that led to another water container.
At this time, the donkey had already accumulated full power for the clockwork. As soon as Xu Yun turned on the switch, the rotor quickly began to rotate.
The volume of the solution he prepared this time was about one liter. According to the Nernst equation, it can be calculated that the theoretical value of the voltage for successful electrolysis is 13V.
Therefore, the effective number of turns of the generator he designed is 17.
Of course.
Xu Yun's preset number of rotor slots is 2, and the speed is 300 revolutions per minute. The calculated accurate value is 15.7, which logically should be 16 revolutions.
However, considering the ancient copper wire and the conduction effect, he still chose to wind it an extra turn to be safer.
After all, if the electrolysis voltage does not exceed 30 volts, it is basically fine.
After all preparations were completed, Cup A started electrolysis.
Although there are still many impurities in the solution at this time, such as magnesium chloride and sodium sulfate, the solution does not seem to be pure.
However, Xu Yun's operation mainly focused on the collection of gases. Sodium chloride accounted for the majority of the solution, so it was not affected by other cations at all.
Just mention it here by the way.
This concept seems easy to understand, but it specifically involves the concepts of superpotential and Gibbs free energy.
Just like a piece of knowledge that everyone knows in middle school:
Electrolysis of dilute sulfuric acid is equivalent to electrolysis of water.
But in the professional...or university field, this statement is actually wrong.
Because in the high school range, the discharge order of hydroxyl radicals in water is before the oxygen-containing acid radicals, so the oxygen-containing acid radicals cannot discharge electricity.
But in fact, due to the existence of overpotential, a side reaction will occur during the period to generate H2S2O8, which exceeds the standard electrode potential of 2.01V, forming an overpotential situation.
Therefore, electrolysis of dilute sulfuric acid is actually different from electrolysis of water.
This chapter is not over yet, please click on the next page to continue reading the exciting content! Realize and return to the original point.
With the introduction of electric energy, the sodium chloride in cup A quickly undergoes electrolysis.
The cathode generates hydrogen gas.
The anode generates chlorine gas.
The generated gases escaped and were collected by a glass tube into a container placed in a dark place where no light could be seen.
Chlorine is at the bottom and hydrogen is at the top.
Ignite and burn, and white mist will form at the mouth of the bottle. (I don’t recommend you try it, as it can easily explode)
The white mist was led by the glass tube to another container filled with water, where it dissolved with water.
Thus.
A higher concentration of hydrochloric acid is now prepared.
Seeing this, some students may ask:
That's not right. If chlorine gas is directly dissolved in water, hydrochloric acid can be obtained. Why bother?
the reason is simple:
The chlorine gas generated by the electrolysis reaction can also be dissolved in water to obtain hydrochloric acid, but this reaction actually generates a mixed solution of chlorine and water.
In addition to hydrochloric acid, there are also Cl2, H2O, HClO, H, ClO-, Cl-, OH- and many other ions.
Not only is the reaction reversible, but the concentration of hydrochloric acid is also very low.
The effect is much worse than the hydrochloric acid prepared by Xu Yun.
Of course.
Again, don’t react with chlorine and hydrogen easily, otherwise an explosion may easily occur.
His gaze returned to its original position.
After the operation was completed, Xu Yun packed the hydrochloric acid.
He glanced at Lao Su next to him, and was not in a hurry to make the next move. Instead, he asked Lao Su:
"Master, can you find someone to catch a few monsters?"
"盱甴? What do you want that thing for?"
"A villain has his own uses."
Lao Su saw a lot of Xu Yun's strange operations today, so he didn't ask any more questions. He glanced at Mr. Xie Duguan beside him and ordered:
"In the first year of the year, you quickly find someone to catch some monsters."
Mr. Xie nodded and turned around to arrange the manpower.
Mentioned it a long time ago.
Cockroaches have been on the earth for hundreds of millions of years. They have a history older than the dinosaurs. They can even be said to be one of the oldest living creatures on the earth.
In addition, the hygiene level in the Song Dynasty was much lower than that in later generations. It was summer again, so naturally cockroaches could be seen everywhere.
So not long after, Mr. Xie came back with a glass bottle:
"Master, Brother Wang, we've caught him."
Xu Yun took the glass bottle and looked at it, and immediately felt happy.
Good guy.
It's the American cockroach again, the same old trickster.
At this time, these American cockroaches were showing their teeth and claws in the bottle. It was obvious that the food in Lao Su's family was good.
Xu Yun then leveled the glass bottle and signaled Lao Su to step aside.
Open the bottle, pick up the hydrochloric acid and pour it into it.
Normally, hydrochloric acid has a strong corrosive effect on organisms, but it is very difficult to kill organisms.
But cockroaches are very special:
There is a protein called tiec on the surface of this thing. The corrosive destructiveness of hydrochloric acid to this protein ranks first among all acids, much ahead of the second one.
Therefore, hydrochloric acid is actually a very effective cockroach killer.
Bang——
With the splashing of hydrochloric acid.
The cockroaches were in a panic at first and crawled around in the bottle.
But soon, their body surfaces were corroded by hydrochloric acid and holes were formed.
In just a few minutes, these unlucky guys finally...
Dying from exhaustion.
American cockroach.JPG.
See this situation.
Lao Su suddenly shrank his pupils and said in horror:
"This...how is this possible? Table salt is actually poisonous?"
Xu Yun smiled slightly when he saw this but said nothing.
Lao Su's reaction was what he expected, or to put it bluntly, this was actually one of his goals:
In ancient times when microscopic cognition was almost zero, there was nothing more impactful than isolating 'poisonous' substances from the refined salt we eat every day.
When the next thing he does is completed, Lao Su will definitely ask him some questions.
And if nothing else, it will definitely involve the microscopic field.
With such an example that happened before us as evidence, some words are obviously more convincing.
Then Xu Yun stored the prepared hydrochloric acid and picked up another thing that Lao Xu had prepared:
Poison heavy stone.
Toxic barium is a barium-containing ore, which was often used in later industrial industries to detoxify barium ore with acid to produce barium chloride.
Xu Yun washed the poisonous stones that had been ground into powder, picked up a small spoon, and dropped them into the hydrochloric acid solution.
Half an hour later.
A bottle of mixed solution was successfully prepared.
Xu Yun began to add sodium hydroxide to it again - this was one of the products of the previous electrolysis. Although there were other cations in it, they themselves were the target products, so they would not affect the reaction process at all.
It really took Xu Yun a lot of effort to make every link closely linked.
As we all know.
In the toxinite solution, the pH when Fe3 is completely precipitated is 3.2, the pH when Mg2 is completely precipitated is 11.1, and the pH when Ca2 is completely precipitated is 13.9. (Paper reference 10.16283/jki.hgkwyjg.1996.06.014)
Therefore, Xu Yun does not need to care about the real-time data of pH value at all, he only needs to observe the precipitation changes during the reaction process.
Another hour passed.
After adding sodium hydroxide dropwise and filtering.
One bottle of standard barium chloride solution.
At this point, the rest is very simple, that is...
Coarse salt purification for junior high school concepts.
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 thing can be seen everywhere in the glass making industry, and its purpose is to remove calcium ions and barium ions from BaCl2.
Finally, add HCl to remove excess NaOH and Na2CO3 - if you have conditions for this process, you can use pH test paper to observe the amount of hydrochloric acid. If not, don't worry about how much you can pour. If there is too much, just evaporate it.
Then another hour passed.
A large cluster of precipitated sodium chloride crystals emerged.
Xu Yun weighed the dosage and dissolved it into the water.
that's all.
A cup of standard concentration saline officially arrived in 1100 AD.
And the other side.
Looking at Xu Yun who was busy tinkering with the preparation of garlic injection, Lao Su finally couldn't help it:
"Xiao Wang, why can salt water be treated in this way to produce such a poisonous substance?"