Eric Flint: Grantville Gazette Volume 24

In 1920, a coal furnace could achieve a temperature of 1600њC without a blast, and 1800њC with one. A gas-fired furnace, with hot air, both the gas and air under pressure, could reach about 2000њC. (Marsh, 46). For higher temperatures, you need to heat by means other than combustion.

An electric arc furnace uses an electric current to heat a conductive material. That could be an ionic compound, or a conductive metal. Perhaps the first industrial use of the electric arc furnace was in the production of calcium carbide by heating lime and coke to 2000њC (1888). Electric arc furnaces came to play an important role in small-scale steelmaking.

Another option for sidestepping the practical combustion temperature limit is to use a solar furnace. Temperatures of 3000њC have been achieved by focusing solar radiation.

The higher the temperature our technology will generate, the more options we have for chemical synthesis.

To chill things down, you can put the vessel in ice, an alcohol bath, dry ice (solid carbon dioxide), or in liquid nitrogen. (for availability of CO2 and nitrogen, see part 2, and Huston, "Refrigeration and the 1632 World" (Grantville Gazette 17)).

Atmosphere Control

Some reactions cannot be conducted in the air, because it would react. If so, the air is replaced with an inert gas, like nitrogen or argon.

Or you may need an atmosphere whose pressure is higher or lower than normal. It is important to compare the number of gas molecules at the beginning and end of the reaction. If that number decreases (as in ammonia synthesis), increasing the pressure will cause the reaction to shift (per Le Chatelier's Principle) in favor of reducing the pressure, which means in favor of fewer gas molecules, and thus in the forward direction. On the other hand, if the number of gas molecules is increased by the forward reaction, then you want to conduct the reaction under lower-than-normal pressure.

To change the pressure, you need two things: a pump, and a vessel with walls strong enough to withstand the pressures generated.

Vacuums may be needed to pull out a gaseous product (to drive a chemical reaction), or to lower the boiling points of the compounds in an organic residue (as in vacuum distillation). Vacuum pumps have been scavenged from refrigerators. (Gorg Huff, "Other People's Money," Grantville Gazette 3)

Elevated pressure also may be used to keep the reactants in the liquid phase, or to facilitate a gas phase reaction. In the mid-nineteenth century, autoclaves were built which could achieve pressures of 725-1150 psi (14.7 psi is normal atmospheric pressure). A 1901 ammonia synthesis used a 1450 psi autoclave. In the early twentieth century, large-scale continuous feed reactors had been built which could handle 2000-5000 psi. By the 1990s, there were operations using 51,000 psi. (Kirk-Othmer/"High Pressure Technology").

High pressure vessels are typically thick -walled, and composed of gun steels. During the 50s, the preferred alloy was nickel-chromium-molybdenum, and later an alloy which additionally contained vanadium gained favor.

The down-timers' only experience with "pressure vessels" is of a rather specialized nature: cannon barrels. These have to resist the internal pressures generated by the explosion. For a given thickness, bronze is better than cast iron, and the down-timers are familiar with the concept of the "built-up" cannon, in which hot hoops or jackets are fit over the barrel and allowed to cool and shrink.

In 1773-91, Woolwich conducted experiments on muskets, reporting a maximum internal pressure of 2,000 atmospheres. (Ingalls). A Civil War era 15-inch Rodman gun, charged with 130 pounds of black powder, will experience 25,000 psi (1700 atmospheres) pressure. (NPS).

While explosives are not exactly a preferred source of pressure (they're dangerous, and don't lend themselves to continuous processing), Alfred Noble "packed steel tubes with gunopowder or cordite and heated them until they exploded with tremendous force, briefly attaining pressures of 8,000 atmospheres at more than 5,000њC." (Hazen 35).

The up-timers include some steam engine enthusiasts, and a locomotive boiler can be considered a high pressure vessel suitable for continuous processing. Canon is a little vague on the issue, but it appears that there is at least one true locomotive on the main line by September 1633 (Flint, 1633, Chapter 33). That locomotive, of course, is generating high pressure steam. I suspect, based on the nineteenth-century locomotive data which the designers will be studying, that it has a steam pressure in the 75-200 psi range. That's still short of even a nineteenth-century autoclave, but it's a start.

To some extent, it will be possible to compensate for having weaker alloys by increasing the thickness of the vessel wall. However, that increases the expense of the vessel and, if it's externally heated or cooled, it impairs heat transfer. In addition, increasing vessel thickness doesn't address the Achilles' heel(s) of the system: the openings needed in order to add raw materials, withdraw product and perhaps supply or remove heat.

Solvents

Solvents are used as a medium in which the reactants can find each other, as catalysts (to help the reactants make or break bonds), and to control the temperature of the reaction. The traditional solvent for inorganic chemical reactions is water.

If cold water doesn't dissolve a particular salt, you can try hot water, and, if that fails, a dilute or concentrated solution of an acid (hydrochloric, sulfuric, nitric, hydrofluoric, acetic, etc.). If need be, the inorganic chemist may have recourse to pure acids, carbon disulfide, liquid ammonia, liquid sulfur dioxide, alcohol, benzene, chloroform, acetone, ether, and turpentine. CRC provides detailed information on the solubility of inorganic compounds in various solvents.

The choice of solvent can have interesting consequences. Barium chloride is soluble in water, while silver chloride is not. The reverse is true in liquid ammonia. Hence, in water, barium chloride reacts with silver nitrate to form silver chloride and barium nitrate. The reverse reaction is favored in liquid ammonia. (Purcell, 154).

Sometimes, not only do you not want to use water as a solvent, you need to make sure that there isn't even a trace of water present in the reactor. If so, you will use various dehydrating agents to prepare the reactor and the reactants for use.

While water was the most important solvent in inorganic chemistry, it has a lesser role in organic chemistry. Over twenty different organic compounds are used as solvents, including methanol, ethanol, acetone, acetic anhydride, pyridine, chloroform, diethyl ether, and benzene (Bordwell 201). In winter 1633-34, Henri Beaubriand-Levesque uses turpentine and ether as solvents for natural rubber. (Offord, "Letters from France," Grantville Gazette 12).

The "aprotic solvents" (e.g., dimethyl sulfoxide) are especially interesting because they seem to increase the reactivity of the reagents (M amp;B 492). DMSO can be obtained from the lignin of wood (EA/Dimethyl Sulfoxide).

Measurement Apparatus

The weight, and hence the mass, of a chemical is measured in chemistry labs by using an equal-arm balance. This has two pans, one holding the unknown, the other a known weight. EA/Balance says that the key to precision measurements is to use a knife edge as a fulcrum, whereas EB11/Weighting Machines warns that the knife-edges and their bearings must be extremely hard. All else being equal, a long arm balance will be more sensitive than a short arm one. Precautions must be taken vis-a-vis temperature, humidity, vibration (from air currents or through the ground), and other disturbances.

In industry, where the weights involved are much greater, the measurement will probably be with an unequal arm balance ("steelyard"), a spring scale, or a platform scale with multiplying levers. (EA/Weighing Machines).