The Knowledge: How to Rebuild Our World From Scratch (25 page)

Crystal radios (as well as rust-and-pencil detectors) are beautiful in their simplicity and don’t need to be plugged into an electricity source, as they derive their operating power from the received radio wave itself. But the cat’s whisker rectifier is unreliable, and crystal sets can produce only very low-power sound. Surprisingly, the solution to this, and a gateway technology for a whole range of other advanced applications, is related to another feature of modern civilization—the light bulb.

Just like a light bulb, a vacuum tube consists of a hot metal filament within a glass bubble, but the vacuum tube, most important, also includes a metal plate around the filament, and the interior is evacuated
to a very low pressure. When the filament is heated white-hot, electrons boil off the metal and form a cloud of charge around the wire. This is known as thermionic emission and is what underlies the functioning of X-ray machines, fluorescent lights, and old-style television and computer screens. If the plate is more positively charged than the filament, these freed electrons are attracted over and a current flows through the device. But current can never flow the other way, as the metal plate is not heated to give off electrons, so such a “diode” (with two metal contacts or electrodes) works like a check valve, permitting current in only one direction. Employing very different physics, the thermionic valve therefore exhibits an identical functionality to the crystal detector and can be put to immediate use as the rectifier in radio receivers. But the crucial innovation, enabling a whole new capability, comes from a simple adornment to the diode.

WIRING DIAGRAM FOR A SIMPLE RADIO RECEIVER (TOP) AND A RAZOR-BLADE RECTIFIER COMMON IN POW RADIOS (BOTTOM).

If you take a standard vacuum-tube diode and add a wire spiral or mesh between the hot filament and the metal plate, you can achieve something fantastic. This three-element device is called a triode, and by tweaking the voltage you apply to the mesh you can influence the current flowing through the tube. Applying a slight negative voltage to the control grid begins to repel the electrons boiling off the filament and streaming to the metal plate; increase the negative bias further and the flow is restricted even more—it’s like pinching a drinking straw to control how much fluid passes up it. Crucially, the triode allows you to use one voltage to control another. But the ingenius application of the arrangement is that tiny variations in the small control-grid voltage can cause large variations in the output voltage. You have amplified the input signal.

This function is unachievable with crystals and can be used to amplify the weak received signal to power speakers and fill a room with sound. It also enables you to generate a pure-frequency electrical oscillation perfect for a narrow-band carrier wave and conveniently imprint
the carrier wave with sound modulation. These are all crucial applications for mainstream radio communications, but just as usefully, vacuum tubes can be used like a switch, far faster than a mechanical lever, to control the course of electricity. Connecting together a large network of these vacuum tubes so that the switches control one another allows you to run mathematical calculations and even construct fully programmable electronic computers.
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ADVANCED CHEMISTRY

I wouldn’t mind if consumer culture went
poof!
overnight because then we’d all be in the same boat and life wouldn’t be so bad, mucking about with chickens and feudalism and the like. But . . . If, as we were all down on earth wearing rags and husbanding pigs inside abandoned Baskin-Robbins franchises, I were to look up in the sky and see a jet . . . I’d go berserk. I’d go crazy. Either
everyone
slides back into the Dark Ages or
no one
does.

D
OUGLAS
C
OUPLAND,
Shampoo Planet
(1992)

THROUGHOUT THIS BOOK
we’ve looked at a few simple ways that you can convert one substance into another. While these transformations between substances with very different appearances may seem like magic at first, with a little effort you can come to understand the behavior of different chemicals, spot patterns in the way they interact with one another, come to predict what will happen in a reaction, and then, ultimately, wield that power of knowledge to control what happens in a complex set of reactions to deliver exactly the outcome that you want.

Later in this chapter we’ll explore how a more advanced civilization, which has secured a stable footing over generations of recovery since the Fall, will be able to employ more complex, industrial processes to provide for its requirements; the rudimentary methods we’ve covered already for producing soda will get you only so far. But first, let’s take a look at how electricity can be used to extract several crucial
commodities for the rebooting civilization, and how it helps us to explore the startling order that underlies the chemical world.

We’ve seen how mastering the generation and distribution of electricity offers a fantastic power source for a multitude of the functions of a recovering civilization and enables communication across vast distances. But the first actual implementation of electricity in our history, and an application that you will also find invaluable early in a reboot, is using electricity for tearing apart chemical compounds to liberate their constituents: electrolysis.

For example, if you shunt a current through a brine (sodium chloride) solution, you’ll be able to collect hydrogen gas bubbling off the negative electrode from the splitting of water molecules, and chlorine gas from the positive. Hydrogen can be used to fill airships and is a raw ingredient for the Haber-Bosch process (to which we’ll come later in this chapter), whereas chlorine is valuable for creating bleaches that you will need to make paper and textiles. And if you’re a little bit clever with the setup, you’ll also be able to extract sodium hydroxide (caustic soda) building up in the electrolyte fluid, which, as we’ve seen earlier, is a fabulously useful alkali. Electrolysis of pure water (with a little sodium hydroxide added to help it conduct electricity) will yield oxygen and hydrogen.

Aluminum, too, can be teased from its rocky ore by electrolysis—it’s too reactive to be smelted using charcoal or coke. It is the most abundant metal in the Earth’s crust and a major constituent of one of the earliest materials to be employed by humanity—clay. Yet it was prohibitively expensive until the development of an effective method
for melting and electrolyzing its ore in the late 1880s.
*
Luckily, a recovering society will not immediately need to purify the metal afresh. Aluminum is so fantastically resistant to corrosion that it will remain uncorrupted for centuries after the apocalypse and can be recycled by melting at the relatively low temperature of 660°C, using the rudimentary furnace we encountered
here
.

By employing electrolysis, you’ll be able to synthesize several substances useful for civilization, leapfrogging past less effective chemical methods that were employed over the centuries. Moreover, electrolysis will also help with your scientific exploration of the world: it decomposes compounds to retrieve the pure building blocks of all substances—the elements. In 1800, for example, electrolysis conclusively demonstrated that water is not an element at all, but a compound of hydrogen and oxygen. And within eight years another seven elements were isolated by electrolysis: potassium, sodium, calcium, boron, barium, strontium, and magnesium. The first three of these were discovered by using electricity to break down commonplace compounds we have used frequently in this book: potash, caustic soda, and quicklime, respectively. And not only is electrolysis a crucial technique for isolating previously unknown elements: the process also demonstrates that the bonds holding atoms together in compounds are themselves electromagnetic in nature.

If you consider the interactions of the different elements, how they tend to behave in reactions with one another—their personalities—you’ll become aware of one resounding, fundamental truth: the
elements aren’t solitary but naturally fall into clusters with similar behaviors, like families. The discovery of this pattern gives structure to the chemical universe, in the same way that the realization of morphological similarities and thus relatedness between living organisms brings order to the biological world. Sodium and potassium, for example, are both violently reactive metals that form alkaline compounds, such as the caustic soda and potash you can electrolytically isolate them from; and chlorine, bromine, and iodine all react with metals to form salts. If you now sort the known elements into an array, lining up those with similar behavior in the same column to represent the underlying repeating pattern, you create the
periodic table of the elements.

The modern periodic table is a colossal monument to human achievement, as impressive as the Egyptian pyramids or any of the other wonders of the world. Far more than just a comprehensive list of different elements that chemists have identified over the years, it is a way of organizing knowledge that allows you to predict details about what you have not yet found.

For example, when the Russian chemist Dmitri Mendeleev first assembled a periodic table in 1869 of the 60-odd elements then known, he found gaps in the brickwork—placeholders corresponding to missing substances. But the brilliant thing about the arrangement, where the elements are placed according to their properties, is that it enabled him to predict precisely what these hypothetical elements would be like—such as eka-aluminum, the missing piece in the table immediately below aluminum. Even though this hypothetical stuff had never been seen or touched, based purely on its location within the array you can predict that it would be a shiny, ductile metal, with a particular density, and that it would be solid at room temperature but melt at an unusually low temperature for metals. A few years later, a Frenchman discovered a new element in an ore and named it gallium, after the old name for his homeland. But it soon became clear that this was the
missing eka-aluminum anticipated by Mendeleev, and that his prediction for the melting point was spot-on: gallium turns from solid to liquid at a temperature of 30°C—the metal literally melts in your hand.
*

This simple truth about the patterns inherent in the elements will help structure your own post-apocalyptic investigations into the makeup of matter and how to best exploit the different properties offered by natural substances. Let’s turn now to build on the lessons from Chapters 5 and 6 and take a look at two useful applications of slightly trickier chemistry—explosives and photography.

You might think that explosives are exactly the sort of technology you would want to leave out of a manual for rebooting civilization, to prolong peaceful coexistence for as long as possible. It is certainly true that explosives can be turned to warmongering (or defensive) ends, and historically their chemistry has developed in tandem with the metallurgy required to safely contain and direct the blast for reliable cannon or firearms. But the peaceable applications are arguably far more crucial for a recovering civilization: explosives are enormously helpful in rifles for hunting, as well as to break open rock faces for quarrying and mining, and for blasting tunnels and canals. And perhaps most important
in a post-apocalyptic world will be the demolishing of dilapidated and unsafe high-rise buildings to cannibalize their structural components and clear the land for redevelopment as the emergent civilization expands back into long-deserted quarters. In any case, scientific knowledge itself is neutral: it is the purpose to which it is applied that is either good or evil.

To create an explosion—a rapidly expanding pulse that assaults your eardrums, shatters a rock face, or pushes over a building—you need to suddenly create a bubble of very-high-pressure air in a small space. And the best way to accomplish that is with a frenzied flurry of chemical reactivity that converts solid substances into hot gases, which take up far more room and so quickly expand outward from the reaction point. A modern rifle, for example, contains roughly a sugar cube’s worth of powder in the charge behind the bullet, but when this is triggered it reacts with itself blindingly quickly to create a ball of gas about the size of a party balloon. The rapid expansion within the claustrophobic confines of a narrow rifle barrel is what creates the enormous force that hurls the bullet at about the speed of sound.

You can get solid fuels to explode by grinding them into a fine powder so that the air has access to a much greater area to accelerate combustion; coal dust and flour burn extremely vigorously (and explosions can occur even at grain elevators). An even better solution is to remove the necessity for getting oxygen from the air, and instead provide plenty of oxygen atoms already in close proximity to the fuel for rapid combustion. A chemical that generously supplies oxygen atoms—or, more generally speaking, is hungry to accept electrons off other chemicals—is called an oxidizing agent or oxidant.

Ironically enough, the earliest explosive to be developed in history was first formulated by ninth-century Chinese alchemists seeking an elixir for immortality: black powder. Gunpowder consists of charcoal—the fuel or reductant—and saltpeter (now termed
potassium nitrate), the oxidant, ground and mixed together. Sprinkling in some yellow elemental sulfur as a third ingredient changes the end products of the reaction and results in far more energy being left over for the concussive whump. An optimized gunpowder recipe is to mix equal parts of saltpeter and sulfur to six parts of charcoal fuel: a chemical cocktail taut with latent energy poised to burst out.

The nitrate ingredient of gunpowder calls for a bit of nifty chemical wheeling and dealing. Historically, the source of nitrates for explosives as well as fertilizers was very humble: a well-matured pile of manure contains hordes of bacteria that have acted to convert nitrogen-containing molecules into nitrates, and you can get these out by exploiting the fact that similar compounds have differing abilities to dissolve in water. It is a fact of chemistry that all nitrate salts are readily water-soluble, and that hydroxide salts are often insoluble. So, soak a few buckets of limewater (calcium hydroxide; see Chapter 5) through a dung pile, and most of the minerals will stay trapped inside as insoluble hydroxides, while the calcium will pick up the nitrate ions and drain out. Collect this fluid and stir in some potash. The potassium and calcium will swap partners to create calcium carbonate and potassium nitrate. Calcium carbonate doesn’t dissolve in water—it’s the compound making up limestone and chalk, and the white cliffs of Dover certainly aren’t vanishing with every wave—but potassium nitrate can. So filter out the chalky white precipitate before boiling away the water to yield crystals of saltpeter. A good test that your isolation has been successful is to soak some of the solution onto a strip of paper and let it dry—if you’ve got potassium nitrate it will burn with a fizzing, sparkling flame.

The chemistry for extracting saltpeter is straightforward enough; the trouble is in finding enough sources of nitrates to use as feedstocks for the process as the demands of your recovering civilization grow. Suitable mineral deposits are found only in very arid environments
(saltpeter is readily soluble and thus easily washed away) such as the Atacama Desert in South America, and bird guano is also very rich. The use of nitrates in both fertilizers and explosives meant that they had become a crucial commodity by the end of the nineteenth century, and wars were fought over tiny barren islands for the bird shit they were encrusted in. We’ll take a look later in this chapter at how to release your developing civilization from the constraints imposed by nitrogen starvation.

While gunpowder supports rapid combustion by intermingling fuel and oxidant powders snugly together, there is an even better way to ensure a more vigorous reaction and thus a more powerful explosion: combining the fuel and the oxidant into the same molecule. Reacting many organic molecules with a mixture of nitric and sulfuric acids (see Chapter 5) serves to oxidize them, tacking on nitrate groups to the fuel molecule. For example, oxidizing paper or cotton (which are both sheets of plant cellulose fibers) with nitric acid produces the heartily flammable nitrocellulose—flash paper or guncotton.

Another explosive more potent than gunpowder is nitroglycerin. This clear, oily explosive is made by the nitration of glycerol, an offshoot of the production of soap, as we saw in Chapter 5, but it is disastrously unstable and liable to blow up in your face at the slightest provocation. The solution that Alfred Nobel found to stabilize its destructive potential was to soak the shock-sensitive nitroglycerin into wads of absorbent material like sawdust or siliceous clay—creating sticks of dynamite. (It was the fortune from this invention that Nobel used to found the famous prizes for contributions to humanity in the sciences, literature, and peace.)

The production of powerful explosives, therefore, relies on nitric acid as a potent oxidizing agent, and this same acid is also required for photography and the capturing of light using silver chemistry.