Chapter 377: Under Low Temperatures
The heating system was not complicated in principle—boil the water, run the steam through pipes, let the radiators bleed warmth into each room. Roland had chosen steam over hot-water circulation because steam ran hotter and moved itself: as long as the boiler stayed lit, pressure would push condensed droplets through the whole circuit without a pump.
The engineering tradeoffs were clear enough. Steam pipes operated under high pressure, and structural failures in high-pressure systems were not failures so much as events. Steam at two to three hundred degrees Celsius caused injuries of a different order than a hot pan. Three precautions addressed this.
First, Anna’s Blackfire welding combined with Soroya’s coating guaranteed joint integrity across every connection—a standard of seal that no conventional smith could have approached.
Second, Roland had designed an automatic pressure valve on the boiler: the same centrifugal governor principle he’d used on the steam engine. When furnace pressure exceeded safe limits, the flywheel’s rotational speed pulled the valve arm upward, releasing steam and dropping pressure automatically.
Third—and this one was the safety engineer’s instinct rather than the careful planner’s—he had asked Anna to score several shallow grooves around the copper fitting between the boiler and the two main supply pipes. The same principle as the perforated tear-lines on tin cans: a calculated weak point. If the pressure valve somehow failed to open, the scored joint would give first, and the failure would be contained inside the annexe rather than traveling through the castle walls.
The system had been running for three days, and the difference it made was total.
Thick winter coats had been set aside. The witches moved through the halls in light autumn garments—talking, laughing, their voices easy in rooms that actually held warmth. Roland found, to his mild surprise, that this had an effect on his own productivity. The girls in their ordinary clothes, comfortable for the first time in weeks, were motivating in a way he had not quite planned for.
The practical matters, however, did not suspend themselves.
His next task was more important than heating pipes and would decide the shape of the Western Region’s future. He needed a path to synthetic ammonia. Dependence on natural nitrate deposits was a ceiling he could not leave in place—it capped explosive production and, downstream, capped ammunition supply. If he wanted automatic weapons in the field by spring, the chemistry had to come first.
He summoned Kyle Sichi and Agatha to his office.
“How have things been between the two of you these past few days?” he asked, keeping his tone light.
The question concealed genuine concern. Kyle Sichi was the chief alchemist of Border Town—brilliant, obsessive, and constitutionally indifferent to other people’s feelings. Agatha came from the Witch Kingdom four centuries gone, had been a senior member of the Quest Society, and had the analyst’s habit of cataloguing everyone she met by their usefulness and their threat level. Her default mode was something between contempt and appraisal. Both of them talked straight and responded badly to anything they read as posturing. Roland had been quietly braced for a collision since the day he put them in the same laboratory.
“Very well,” Kyle said.
Roland looked at him.
“Miss Agatha’s ability has been essential to our work. We’ve confirmed the stable synthesis temperature for nitration glycerol and successfully prepared it in the laboratory—we’re currently testing conditions for industrial-scale production. None of this would have been possible without the ice cups.” He paused. “I apologize—I should have reported this earlier. I forgot while I was busy.” A beat. “If you called me here specifically to ask about this, may I return to the laboratory? There is still a great deal to do.”
Roland turned to Agatha. She nodded.
“Sir Kyle has an exceptional foundation of knowledge—particularly regarding the elements. In structure, it resembles the Quest Society’s own framework, which makes working together straightforward. If he had lived in Taquila, the Union would almost certainly have accepted him.”
Two straight-talkers, and they got on fine. He had miscalculated, apparently—had assumed abrasiveness would compound. Instead it had found its complement. And why did Kyle seem more deferential toward Agatha than toward his own lord? Roland pushed that particular question aside.
“Good. Then I’ll assign you something new.” Kyle’s posture changed immediately—the slight forward lean of someone who has heard a word they like. “As I’ve mentioned before, the air around us contains multiple gases we haven’t yet put to use. It’s time to start. According to Elementary Chemistry, oxygen and nitrogen together make up ninety-nine percent of atmospheric air. I need them separated for chemical production.”
Kyle was quiet for a moment. “Separation by physical properties—different boiling points, different melting points?”
“Exactly. Cool the air until it liquefies, then heat it gradually. Since nitrogen’s boiling point is lower than oxygen’s, it vaporizes first and can be drawn off separately. The temperatures required are well below the freezing point of water, which makes conventional apparatus useless.” Roland looked at Agatha. “Your ability is the key.”
“Turning air into liquid.” Kyle stroked his beard. “That is genuinely interesting.”
“If you bring the temperature low enough, the gases solidify entirely,” Roland said. The thought clearly delighted him—that something as invisible and ubiquitous as air could be held in a cupped hand, cold enough to burn.
Agatha frowned slightly. “I read through the same book, but I didn’t see anything about air freezing into distinct gases.”
“They mix uniformly, which makes visual separation impossible,” Roland explained. “The process begins with eliminating carbon dioxide—it has the highest freezing point of the common atmospheric gases, but it makes up less than one percent of the total, so its solid form is barely detectable. After that, oxygen and nitrogen condense together and take on a faint blue color. Without active separation, they appear as a single pure substance. Liquid nitrogen, however, is colorless—which is how you can distinguish the composition as the process runs.”
“What’s the first step?”
“Build the distillation vessel.” He pulled out a diagram. “This is the most consequential part.”
Glass was out of the question—it shattered under repeated thermal cycling. The vessel had to be steel, which meant solid walls and no direct observation of the interior. Anna could fabricate the shell, but watching the liquefied air behavior during heating would require Sylvie’s Eye of Magic as a substitute for a window. Agatha would control the temperature and record magic consumption at the nitrogen boiling point; once they identified the stable separation temperature, they could work toward reproducible conditions.
They would also need Agatha’s ability at a level of precision she had not yet been asked to demonstrate in this particular application.
Preparation took three days.
When the vessel was finished, Roland went down to the chemistry laboratory himself to oversee the first oxygen-nitrogen separation experiment Border Town had ever attempted.