Chapter 18. Spot and Roebuck (Acid)


Now, as I told you above, this saltpeter is extracted from the above-mentioned manurial soils and from dark places that have stood turned over and loosened for a long time, provided the rain have not been able to quench the earthy dryness. The best and finest of all saltpeters is that made from animal manure transformed into earth in the stables, or in human latrines unused for a long time. Above all the largest quantity and the best saltpeter is extracted from pig dung. This manurial soil, whatever kind it may be, should be well transformed into a real earth and completely dried of all moisture; indeed it should be powdery if you wish it to be good. Assurance that it contains goodness is gained by tasting with the tongue to find that it is biting, and how much so. If you find from this trial that it has a sufficient biting power so that you decide to work it and you have found a quantity of it, it is necessary to provide yourself with kettles, furnaces, vats, or chests, and also with wood, lime, soda ash, or ashes of cerris or oak, and especially with a large hut or other walled space near water.

 — Biringuccio, Pirotechnia, ca. 1540 AD [1]


Crap! Now that's a business to be in. You take something that everybody's got and nobody wants and turn it into something that every government needs if it's going to be a government for any time at all. Maybe you remember from Chapter 12 that bacteria make ammonia whenever crap and piss sit around without much air, which is why outhouses and latrines smell like ammonia. Well, when there's plenty of air, instead of making ammonia they make nitrates, which don't smell at all. And that's why compost heaps don't smell bad as long as they're getting plenty of air. It's those nitrates in compost, stables, and latrines that the government needs for making saltpeter. Only problem is, how do you get the nitrates out?

Perhaps you are wondering why the hut or other walled space in which you will process your manurial soil should be near water. I will tell you. First of all, you will recall from Chapter 7 that all nitrates are soluble and that most hydroxides are insoluble, with the exception of calcium hydroxide which is, of course, soluble in water. So when lime water, that is to say a solution of calcium hydroxide, percolates through manurial soil, virtually all of the minerals stay behind as insoluble hydroxides and the water which dribbles out the bottom contains soluble nitrates, chiefly calcium nitrate. Throw in some wood ashes, which naturally contain potassium carbonate, and a classic metathesis reaction occurs with calcium carbonate precipitating out and potassium nitrate remaining in solution. Boil away the water and potassium nitrate recrystallizes just as potassium carbonate did in Chapter 8. The result is purified saltpeter.

Now, the government needs sulfur as well as saltpeter if it's going to make gunpowder. Sulfur ore is a kind of yellow dirt or rock that's just a mixture of elemental sulfur and whatever dirt or rock it happens to be mixed with. You can separate out the sulfur on account of its melting point is lower than the melting point of most other kinds of dirt and rock; just heat it up and run the molten sulfur off as a liquid. And if you really want to do it up right, you can distill that sulfur the same as you did alcohol in Chapter 16. So now you have saltpeter and sulfur, which just leaves charcoal. You get charcoal by charring wood in the absence of oxygen and that gives you everything you need to make gunpowder, which is a pretty good business.

Second of all, you must know that "oil of vitriol" had been manufactured in Saxony in small quantities beginning approximately 1630 AD. This oil, now known as sulfuric acid, was used to make hydrochloric and nitric acids for parting precious metals from base metals. Vitriol is a rather uncommon, glassy, green mineral which results from the weathering of iron pyrites, one of the ores of iron. When heated, vitriol decomposes into iron oxide, used as a pigment, and the aforementioned sulfuric acid. Vitriol being relatively scarce, acid was expensive. But there was little incentive to find a less expensive source because assayers required only small quantities of acid.

Then acid got mixed up in drugs.

I was getting to that. About 1689 or so, a fellow named Rudolf Glauber discovered how to make Glauber's salt from sulfuric acid. He ascribed all kinds of miraculous qualities to it and, being something of a quack, began to prescribe it for everything from impotence to venereal disease. This "wonder drug" did no actual good, but unlike most medicines of the day, it did no particular harm and so it passed from quack to quack—

Just like a spider.

More like a dogma, really.

Like a spidery dogma maybe, from one quack to another until it landed in a fellow named Joshua Ward, known to his enemies as "Spot," on account of his Gorbachevity birthmark. Spot had started out being a politician but when that didn't work out, he had to be a quack instead. Now, he didn't want to be a little backwater quack, he wanted to be a big-city man-about-town quack and he opened up a fancy London practice in 1733. He needed a boat-load of Glauber's salt and, the vitriol market being what it was, he hunted through his old chemistry books for inspiration. He found out you could make sulfuric acid from saltpeter and sulfur, which nobody ever did, what with the high demand for gunpowder and the low demand for acid. So Spot went into the sulfuric acid business in 1736, making it by the pound from saltpeter and sulfur instead of by the ounce from vitriol. Even though sulfur and saltpeter were not cheap, they were cheaper than vitriol and so he was able to sell that pound of acid at the same price that everybody else charged for an ounce and still turn a tidy profit.

Meanwhile, back in Saxony one Bergrat Barth discovered in 1744 that indigo reacts with sulfuric acid to produce a water-soluble blue dye. You will, of course, remember from Chapter 12 that indigo was an extremely important dye, but that compared to other dyes its application was quite tedious, involving the anaerobic fermentation of the insoluble dye in stale urine. The new "Saxony blue," or "indigo carmine," was an instant hit with dyers, who were soon crusading for more acid. By mid-century Saxony was producing about 20 tons per year of admittedly expensive acid from vitriol.

Now, Spot could make acid a lot cheaper than the Saxons, but he couldn't make that much of it. See, sulfuric acid eats through most metals so he had to make it by burning sulfur and saltpeter under fifty-gallon glass jars, which were pretty damn big, as jars go. He kept adding more and more jars to his business, trying all the while to keep his process a secret, but that secret didn't want to be kept.

In no time at all a Birmingham doctor named John Roebuck became a convert to the fellowship of saltpeter and sulfur. Poring through the Glauberian scriptures, he found a passage to the effect that sulfuric acid does not react with lead. So he lined wooden boxes, or "chambers," with lead foil to produce acid-resistant reactors which were neither as expensive, nor as fragile as Ward's glass jars. And these "lead chambers" could be built much larger than the jars of the day. Roebuck set up his own acid works in 1746 and began producing chamber acid by the hundreds of pounds—

But the upstart refused to pay royalties on Spot's patent—

Which was understandable, since the patent was not filed until 1749, three years after Roebuck started manufacturing acid—

Which acid was made by a process inspired by Spot, who had started in 1736. Spot sued.

Which drove Roebuck from Birmingham to Edinburgh, the home of a large textile industry. The Scottish bleachers found the now inexpensive sulfuric acid to be an excellent bleach for cotton and linen. Roebuck's Prestonpans Vitriol Company began to produce acid by the ton, and with economies of scale the price of acid fell to a quarter of the price demanded by Ward.

Which increased demand. But Roebuck was no better at keeping secrets than Spot was and pretty soon everybody and his dog had a chamber acid plant. The French had one by 1768 and four more by 1786.

By 1800 the Prestonpans works comprised 108 chambers with a total capacity of 60,480 cubic feet and there was another at Burntisland with a capacity of 69,120 cubic feet. Worldwide annual acid production was reckoned by then in the hundreds of tons.

And by 1913 it would top 10 million tons of acid per year. These days, sulfuric acid is the king of chemicals, the big enchilada, numero uno. In other words, more sulfuric acid is produced than any other chemical in the world. Not bad, for something that came out of the dung-heap.



Reference [3], p. 405.