Chapter 340 - Acids and Bases (III)

Production safety was Ji Situi's greatest headache. Chemical plant accidents differed fundamentally from those in ordinary enterprises: beyond worker casualties, there was equipment damage to consider—and the terrible consequences of chemical leaks were impossible to predict. The casual attitude these former farmers displayed toward hazardous materials overwhelmed him. He conducted safety education sessions repeatedly and severely reprimanded several workers who had neglected to wear protective equipment.

The offenders stood with heads bowed while Ji Situi berated them for a solid half hour. Given Lingao's climate, working by the furnace in full protective gear was admittedly torturous. Fiberglass leggings, rubber aprons, long-arm gloves, high boots—everything was airtight. Even away from the furnace, a few minutes in this equipment left one drenched in sweat.

"Do you want to end up like this?!" Ji Situi produced a medical atlas—borrowed from the Grand Library—and thrust it before them. Every photograph depicted victims of chemical burns.

But the images proved too effective. Their horror had the opposite of the intended result: several indigenous workers came begging to be released from this work. Ji Situi nearly choked with frustration.

After a round of reassurances, promises, and threats—refuse to work and you'll be sent to the Labor Reform Team to experience Fu Youdi's legendary whip—he finally stabilized morale in the sulfuric acid workshop. Only then could he extract himself and hurry to the caustic soda workshop. Outside the building, piles of water vats in various sizes had accumulated alongside heaps of salt. Bing Feng was leading a team through equipment installation.

"Salt, tap water, and vats are all here. While we wait for engineering to finish, let's start mixing saturated brine," said Bai Yu, who had volunteered to bring students to assist. Though now a teacher, his enthusiasm for chemistry remained undiminished.

"This salt won't work." Xu Yingjie shook his head. "Crude salt—far too many impurities."

The principle of electrolyzing salt to produce caustic soda was simple enough: direct electrolysis of saturated brine decomposed sodium chloride into sodium hydroxide—caustic soda—while simultaneously liberating chlorine gas and hydrogen. But the salt from Yanchang Village was unrefined crude salt, containing not only sodium chloride but also potassium salts, magnesium salts, sulfates, and other impurities. These contaminants would degrade electrolysis efficiency and damage the precious electrodes.

Crude salt therefore had to be purified before electrolysis—stripped of impurities to become a pure saturated sodium chloride solution. Modern industrial systems featured extensive division of labor; caustic soda manufacturers could simply purchase purified sodium chloride as a finished product. Here, everything had to be done in-house. The more primitive the industrial base, the greater the demand for self-sufficiency.

Ji Situi began by analyzing the salt shipment. The quality from Yanchang Village proved quite high; sulfate content—the component most damaging to electrolysis—was extremely low. This was excellent news. The industrial method for removing sulfates required barium chloride, which he lacked. Barium chloride was also highly toxic; even if synthesis were possible, he would have preferred to avoid it. Calcium and magnesium salt content was also low. The salt was ideal for industrial purposes.

He directed workers to pour baskets of crude salt into settling tanks. Water was added until the solution reached saturation. Bai Yu, responsible for refining the electrolyte, then added measured amounts of soda ash and caustic soda in proportions matched to the tested brine composition. These additions reacted with dissolved calcium and magnesium salts to precipitate calcium chloride and magnesium hydroxide. The clarified liquid above was the saturated sodium chloride solution required for electrolysis. Because soda ash and caustic soda had been added, a small quantity of dilute hydrochloric acid was then used for neutralization treatment.

Industrial electrolysis was a continuous process; saturated sodium chloride solution had to be fed into the electrolytic cells without interruption. Brine purification therefore operated continuously alongside it.

Purifying brine vat-by-vat—the intermittent method—was simple in terms of equipment and operation but demanded enormous labor. Industrial practice favored continuous purification. Though Ji Situi was working with indigenous methods, he was determined to automate as much as possible.

Given the available infrastructure—specifically, the presence of a tap water supply—Ji Situi designed a continuous salt dissolution process. Water flowed in through the bottom of a specialized dissolution tank, percolated up through the salt layer inside, and overflowed from an upper outlet. Salt was added intermittently by hand to maintain a consistent salt layer. The resulting brine, fully saturated, was then directed from the dissolution tank to a settling tank for neutralization treatment.

To reduce labor requirements, the tanks were arranged in a stepped configuration—each positioned higher than the last—allowing gravity and siphon principles to move the brine along. The sequence ran: Dissolution Tank → Settling Tank → Neutralization Tank. The saturated sodium chloride solution emerging from the Neutralization Tank was finally directed to the Heating Tank.

This system was simpler than standard industrial designs and required no mechanical assistance. A handful of workers could manage it easily.

"So making caustic soda requires adding caustic soda!" Bai Yu observed, leading his students through the brine preparation process.

Xu Yingjie laughed. "Those are two entirely different things. You're preparing purified brine—that's worlds apart from manufacturing caustic soda."

"Good thing we brought substantial chemical stocks," Bai Yu reflected. "Without them as primers, we'd never have gotten started."

"Not necessarily." Ji Situi watched the reaction progress in the tanks. "It would just mean heavier electrode damage. Pure physical purification of sodium chloride isn't impossible—but it would require massive investment, starting with a complete overhaul of the salt industry equipment at Yanchang Village."

"Hasn't Yanchang Village already been modified extensively?"

"Engineer Wang's modifications focused primarily on increasing output—windmill-powered brine lifting, spray-drying to shorten concentration time." Ji Situi had visited Yanchang Village several times on business.

"Purification would be out of the question without a boiler." He paused. "The Planning Committee originally proposed building a Refined Salt Factory here in Bopu. Once our caustic soda workshop is operational, that project needs to move forward."

"Construction climax for the chemical industry!" Xu Yingjie exclaimed.

"It's our turn at last. Consider what's coming: pesticides, chemical fertilizers, explosives, medicine. Once we have those Four Magic Weapons, global domination becomes plausible!" Bai Yu's enthusiasm was irrepressible.

"That's still far off—don't expect to grow fat on a single meal," Ji Situi cautioned. "We'll need extensive supporting facilities and equipment. Real-world production problems have to be solved incrementally. Take the first batch of sulfuric acid from our workshop: impurity content is very high. In certain chemical processes, that's extremely dangerous. Improving purity requires meeting many additional conditions."

He offered an analogy: "It's like assembling a jigsaw puzzle. Making the Three Acids and Two Alkalis only gives us the four corner pieces. We can see the shape of the picture now—but completing it will take a very long time."

Xu Yingjie added his own: "It's like using glycerol from saponification to mix nitroglycerin. The theory is sound, but in practice, people die."

The brine reaction and precipitation process required twenty-four hours. Ji Situi used the interval to visit the lime kiln. Quicklime was already prepared and waiting. Using data from the process manual, he calculated how much chlorine gas seventy-two hours of continuous production would generate and how much slaked lime would be needed to absorb it. He weighed out the required quantity of quicklime, then directed workers to slowly spray water over it, allowing it to slake gradually. Once slaking was complete, the lime was sifted, loaded into baskets, and transported to the caustic soda workshop.

Ji Situi asked Xu Yingjie to measure the moisture content of the slaked lime: approximately three percent. Slightly high. He ordered the lime piled under a shed for several days. Some quickite remained in the slaked lime; residual moisture would continue the slaking process, reducing moisture content below the optimal one percent within a few days.

When all preparations were complete, the next day revealed a thick layer of white sedite at the bottom of the brine purification tank. Testing confirmed the clarified liquid above met electrolysis requirements. Using siphon principles, Bai Yu transferred the clarified saturated sodium chloride solution to the Heating Tank. Ji Situi lit a fire beneath it, heating the brine to 70°C to drive off dissolved carbon dioxide.

The white precipitate in the settling tank was collected; its main components were calcium chloride and magnesium hydroxide. Both were valuable chemicals and couldn't be discarded. Calcium chloride was particularly useful: the pharmaceutical factory could manufacture calcium chloride injections and tablets for treating hypocalcemia-related conditions. Industrially, it served as a common desiccant, a construction antifreeze, a refrigeration coolant, and a deinking agent for waste paper. It could even be used to coagulate tofu.

Ji Situi exploited the differing solubilities of the two compounds to separate them—calcium chloride dissolved readily; magnesium hydroxide was insoluble. Adding water dissolved the calcium chloride, which was then poured off for separate processing. The insolite portion was magnesium hydroxide. Though less versatile than calcium chloride, magnesium hydroxide could substitute for caustic soda and lime as a neutralizer for acidic wastewater, served as an anti-corrosion and desulfurization additive for oils, worked in insulation materials, and functioned as a flame retardant in construction. It was also an excellent desulfurization agent—exactly what Ji Situi's sulfuric acid workshop needed for its flue gas treatment.

The heated sodium chloride was easily pumped into the electrolytic cells. Ji Situi pulled the switch, and electrolysis commenced. Wearing an anti-shock protective suit and rubber-soled shoes, he tested around the cells and across the workshop floor with a voltage pen. No current leakage detected.

Electrolyte began dripping from the outlet. The color was clear—no alarming black liquid. He waited five minutes, calculating whether the flow rate was normal. Finally, he measured the temperature and voltage inside the tank. Everything was within parameters. Temperature and voltage directly determined electrolysis efficiency.

"What's coming out—that's caustic soda solution, right?" Bai Yu asked.