In the 21st century.

Compared to hand-cranked generators, the concept of electrolysis might be more widely disseminated.

Especially the electrolysis of saturated saltwater, which is a fundamental chemical practical reaction.

In electrolysis experiments, the cathode undergoes a reduction reaction, gaining electrons.

The anode, on the other hand, undergoes an oxidation reaction, losing electrons.

Simultaneously, after the electrolysis reaction occurs, some active metal's non-oxygenated acid salt will generate a base at the cathode.

While the non-active metal's oxygen-containing acid salt will generate acid at the anode.

Additionally, after the electrolysis reaction, the cathode will also produce solids and reducing gases.

As for the choice between cathode and anode...

A common operation for the electrolysis of saturated saltwater is using copper as the cathode and carbon rods as the anode.

Of course.

If conditions are general, actually two carbon rods won't have much impact.

However, the electrolysis of saturated saltwater has a rather special aspect, which is that chlorine gas easily reacts with sodium hydroxide.

Namely, 2NaOH + Cl2 = NaCl + NaClO + H2O.

Therefore, in modern industry, a permeable diaphragm is commonly used to separate the anode chamber from the cathode chamber, preventing them from contacting each other.

However, in the current Great Song, achieving such a technique is clearly impossible, therefore Xu Yun considered.....

A salt bridge.

In the courtyard.

After preparing the generator materials, Xu Yun turned around and asked Old Su:

"Master, do you know where the white crystals bought from the Sour Plum Shop are?"

Old Su pointed to a package on the left and replied:

"That package over there, Xiaowang, if my judgment isn't wrong, this should be saltpeter?"

Xu Yun walked over to open the package, examined it carefully, and confidently said:

"Yes, it indeed is saltpeter.

I heard that old man speak with a He Xi accent, so these saltpeter must have been transported from He Xi."

Old Su nodded thoughtfully and said:

"I see, no wonder when Mr. Xie came back in the First Year he told me that the couple initially thought he was a spy sent by a competitor and even threatened to report to the authorities.

Later, he had to show the Commandery Prince's Mansion's badge and invited a government official from the street as proof before they were willing to sell him some of the crystals, and the price wasn't low."

Xu Yun was quite satisfied as he shook the saltpeter in his hand and said:

"For saltpeter of such quality, it's normal to be expensive, it saves a lot of trouble."

Previously, upon seeing ice-cold sour plum juice in the Sour Plum Shop, Xu Yun had thought of two possibilities for the old man's ice-making.

One is an ice cellar.

The other is saltpeter.

The likelihood of an ice cellar isn't very high, after all, in this era, the cost to build an ice cellar isn't low, only large families and estates would use ice cellars to store ice cubes.

Therefore, although Xu Yun couldn't be sure the other party definitely had saltpeter, he was about seventy percent confident.

And with saltpeter, he could prepare potassium nitrate.

Students who didn't fail biology should remember.

Potassium nitrate is a common salt bridge.

A so-called salt bridge refers to something that can connect the electrolytes in two beakers, allowing ions to move freely from cathode to anode.

With a potassium nitrate salt bridge, it can maximally prevent the chlorine gas and sodium hydroxide produced in electrolyzed saltwater from reacting in the electrolysis cell, thereby promoting the production of chlorine gas.

As for the preparation of potassium nitrate, it's quite simple:

First, dissolve the saltpeter in water to remove sand and mud.

Heat, evaporate, and concentrate, then cool to obtain KNO3 crystals.

Potassium nitrate crystals have extremely high solubility, so by dissolving these crystals in water again, a salt bridge is thus formed.

After many preparatory tasks are completed.

Xu Yun put the refined salt prepared by Mr. Xie into the water and started stirring with a glass rod.

Soon.

The solution began to become somewhat turbid.

Xu Yun looked at Old Su:

"Master, could you please fetch the gauze?"

Though Old Su didn't quite understand Xu Yun's intentions, he still handed him a funnel with gauze over it.

Rustle—

Xu Yun poured down the turbid solution.

With the barrier of the gauze, some insoluble impurities were filtered out.

Next, he divided the filtered solution into two large cups, let's temporarily call them Cup A and Cup B.

Hmm.

Just cups, not shield characters.

Then he first connected Cup A to the electrolysis equipment— the setup wasn't much different from modern equipment for the electrolysis of saturated saltwater, where the anode had a conduit leading to another container of water.

At this time, the donkey had already accumulated power for the mainspring, and as Xu Yun flipped the switch, the rotor began to spin rapidly.

The prepared solution had a volume of about one liter, and based on the Nernst equation, the theoretical voltage value for successful electrolysis was calculated to be 13V.

Thus, the effective turns of the generator he designed were 17 turns.

Of course.

Xu Yun preset the rotor slot number as 2, with a rotation speed of 300 rounds per minute, and the calculated accurate value was 15.7, so theoretically it should be 16 turns.

However, considering the ancient copper wire and conduction effects, he still chose to wrap an extra turn, just to be safe.

After all, a voltage of less than 30 volts in electrolysis generally doesn't pose any issues.

After all preparations were completed, Cup A began electrolysis.

Although at this time there were still many impurities in the solution, such as magnesium chloride and sodium sulfate, making the solution seem impure.

Xu Yun's main focus in this operation was gas collection, as sodium chloride was the primary component of the solution, and other anions wouldn't affect it at all.

A side note here.

This concept seems easy to understand, but it specifically involves concepts of overpotential and Gibbs free energy.

Just like a piece of knowledge everyone knows from middle school:

Electrolysis of dilute sulfuric acid is equivalent to electrolysis of water.

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