Desperate people, accept the seed of my soul!

The zinc powder was ground into a finer powder under the agate mortar, producing a fine rustling sound.

As Shen Hanzhou watched Jiang Yubai grind zinc powder, he suddenly remembered that his senior sister had the same habit when she was alive—grinding zinc powder with an agate mortar and pestle, round and round, for a full ten minutes each time.

At that time, he felt that his senior sister was being too serious. Couldn't they just use the zinc powder that was bought on the market?

I only realized now that it won't work.

Because the zinc powder provided by the Five Sacred Mountains Association is never fine enough.

In his official report to the Five Mountains Association, Shen Yanhui wrote, "Zinc powder reduction method, yield 78 percent."

However, she wrote in her experimental record that "it must be self-ground to a fineness of 400 mesh or higher, otherwise the yield will be less than 60 percent".

The difference between these two data points is the significance of her working overtime alone at the lab bench until the early hours of the morning.

"It's done."

Jiang Yubai poured the zinc powder, as fine as flour, from the agate mortar into the weighing paper. "400 mesh. That's enough."

The reduction reaction takes place in an ammonium chloride solution.

Add the zinc powder in batches, stirring with a glass rod after each addition until the solution changes from gray back to colorless.

Jiang Yu added zinc powder four times, and each time the stirring time was twice as long as the standard operation.

"The temperature cannot exceed 40 degrees Celsius. If it exceeds 40 degrees Celsius, it will undergo excessive reduction, reducing the nitro group to an amino group and then continuing to reduce it."

She stared at the thermometer, a fine layer of sweat beading on her forehead. "This is what Yan Hui wrote in the footnote—the official report from the Five Mountains Association says 'room temperature reaction,' but she said that ice packs should be added when the room temperature exceeds 30 degrees Celsius. Although the room temperature is not high today, the reduction of zinc powder is an exothermic reaction, and the solution temperature will rise on its own."

Just as she finished speaking, the mercury column in the thermometer jumped to thirty-eight degrees.

She took an ice pack out of the salt bath and stuck it to the outside of the reaction flask.

The mercury column in the thermometer stopped rising and began to slowly descend.

"Senior sister, you can recite all these footnotes by heart."

Shen Hanzhou said.

"It wasn't memorized. It was done."

Jiang Yubai said, his eyes fixed on the thermometer, "Two months before her accident, she came to Chaoyang Biotechnology to see me once. She called me into the corridor and handed me a sealed file folder. She said that if anything happened to her, I should connect the data in the folder with the USB drive she left with me. She also said—'Jiang Yubai, you are smarter than me, but you are more likely to trust the wrong people. Don't trust the Five Mountains Society, don't trust Xiong Bei, only trust the data.' At the time, I thought she was just talking nonsense because she was too tired. Two months later, she died, and I realized that was her last words."

Jiang Yubai's voice finally cracked when he said the last sentence.

She paused for a moment, then removed the ice pack from the reaction flask and placed it back into the ice-salt bath.

I owed her a "I'll remember this" message, but I didn't get a chance to say it.

After the reduction reaction was completed, the reaction solution was filtered and concentrated to obtain a light brown amino intermediate.

Jiang Yubai transferred the intermediate to the desiccator and wrote down the second line of data in the experimental record book.

"The yield is estimated at 75%. She wrote 78%, a difference of 3 percentage points. It could be that the zinc powder is not active enough, or the ammonium chloride is not pure enough."

"That's enough."

Shen Hanzhou said.

"Not enough. She said that the yield at each step affects the yield at the final step. If the first step is 82%, the second step is 75%, and the third step is also only 75%, the total yield is only 46%. Less than half."

Jiang Yubai flipped to the last page where Shen Yan returned the correct parameters.

The last page was a handwritten total yield calculation table, with blue ballpoint pen handwriting filling the entire page.

The theoretical yield, actual yield, and factors affecting the yield of each intermediate are clearly listed.

The bottom row of the table says, "If the overall yield exceeds 50%, you can do three batches. If you can't do three batches, do one batch if you have to. Don't worry about cost or time. Just get the reagent made."

"She's urging me."

Jiang Yubai said, pointing to the line of text, "He's been dead for three years and he's still urging me."

The acetylation reaction is carried out in dichloromethane.

When Jiang Yubai measured dichloromethane with a graduated cylinder, he deliberately brought it to his nose and smelled it.

"It doesn't smell sour. Dichloromethane decomposes into hydrogen chloride and phosgene if left for too long, so it can't be used if it smells sour. That's what she taught me—she said the solvents in the Wuyue Association's warehouse often expire, so you have to smell them before using them."

The acetylation reaction requires the addition of triethylamine as an acid-binding agent.

Jiang Yubai picked up the triethylamine reagent bottle, glanced at the label, and then put it down.

"She used potassium carbonate, not triethylamine."

She found a bottle of potassium carbonate in the pile of reagents, weighed out three grams, ground it into powder, and slowly added it to the reaction solution.

"Triethylamine conflicts with the final amination reaction, producing a byproduct that is very difficult to remove. She said she tried four acid-binding agents before discovering this problem, but the people at the Five Mountains Association didn't listen and directly wrote triethylamine in the official report. She used potassium carbonate, and the yield was twelve percentage points higher than that of triethylamine."

Shen Hanzhou sat beside him, watching Jiang Yubai carry out Shen Yanhui's "habits" one by one.

There is a reason behind every habit.

Every reason was the result of countless failed experiments.

Shen Yanhui did not include the results of these failed experiments in his official report to the Five Mountains Society.

She only wrote it onto that USB drive, which could only be read by people in the same group.

"She left this data with you, not for me."

Jiang Yubai suddenly said without looking up, "The USB drive is with you. The correct parameters are with you. She sent you to me so I could help you get the data working. Once it's working, the medicine is yours."

"The medicine is for both of us."

Shen Hanzhou said, "You owe her, and I owe her too. We'll pay it back together."

Once the acetylation reaction is complete, all three sub-reactions of the first step are finished.

Jiang Yubai placed the three intermediates side by side on the lab bench and shone a flashlight on each of them.

The nitration product is a light yellow needle-like crystal.

The reduction product is a light brown powder.

The acetylated product is a white, flaky crystal.

"The first step is complete. Next is the second step—the introduction of chiral epoxy groups. This step is the most difficult in the entire synthetic route. The temperature must be controlled precisely to ±0.5 degrees Celsius, and the pH value must be maintained at 7.4. If it exceeds 7.6, the epoxy groups will open the ring. After the ring opens, the product is directly discarded and cannot be recovered."

"What did my senior sister write in her footnotes?"

She wrote: "Use a pH meter, not test strips. The pH test strips provided by the Five Mountains Association are not accurate enough, and the color determination relies entirely on the naked eye. You can't see a deviation of half a pH unit. You must use a pH meter, and you must calibrate it three times with standard buffer solution first."

Jiang Yubai took out a portable pH meter from his portable equipment case and inserted it into the standard buffer solution for calibration.

It was checked three times.

Record the calibration value for each iteration, and the deviation between the three values ​​should not exceed 0.02.

"Calibration complete. Proceed to step two."

Shen Hanzhou and Jiang Yubai sat side by side in front of the old laboratory table.

The portable workstation's screen scrolled through the experimental records Shen Yanhui had left behind three years ago.

The low-frequency hum of the ventilation ducts echoed through the empty factory.

It was already daylight outside the window, and the morning light cast dappled patterns of light on the lab bench through the gaps in the ivy.

Shen Hanzhou took out his senior sister's photo from his inner pocket and placed it on a corner of the lab table.

The photo shows Shen Yanhui standing in front of the fume hood, smiling back, her goggles pushed up to her forehead.

"Senior sister."

Shen Hanzhou said softly, "The potion is being prepared. Wait a moment. Once it's done, go kill Zheng Daoyuan."