Salt

by Mark Kurlansky

  San Francisco Bay salt was considered of low quality, and it did not compete easily with Liverpool salt, which came as ballast on the British ships that bought California wheat. Coarse salt was also regularly imported from China, Hawaii, and numerous places in South America.

  But in 1859, something happened that drove salt prices back up. In western Nevada near the California border, a three-and-a-half-mile stretch of the Sierra Nevada mountains was found to hold the richest vein of silver ever discovered in the United States. It was called the Comstock lode, named after an early investor who had sold out before the extent of the vein was known. The silver ore was being separated by a technique similar to the sixteenth-century Mexican patio process, and it required mountains of salt.

  By 1868, only nine years after the discovery of the Comstock lode, eighteen salt companies were operating in the south bay. To keep the profit margin high, the salt was mostly harvested by Chinese laborers, the cheapest source of labor in California at the time. The salt workers wore wide wooden sandals to avoid sinking in the thick layer of white crystals.

  After a few years of scraping, the area was running out of naturally evaporated salt, and the salt producers started building successive artificial ponds, pumping the water from one pond to the next by the power of windmills.

  Fortunes were being made on the silver in Nevada and on the salt in California. Then, in 1863, a man named Otto Esche came up with a scheme to make money on the link between them. The salt was shipped inland and into the Sierra Nevadas in horse-drawn carts. Esche went to Mongolia, even today one of the more remote corners of the earth, and bought thirty-two Bactrian camels. Esche apparently knew something of camels since he chose the more docile two-humped camel rather than the notoriously temperamental dromedary of the Middle East. Bactrian camels, since before Marco Polo’s time, had been carrying goods, including salt, across the brown, wide, Mongolian desert.

  A nineteenth-century photograph of a windmill pumping brine into a saltworks in south San Francisco Bay. The Bancroft Library, University of California, Berkeley

  The first discouraging surprise was that only fifteen camels survived the cross-Pacific voyage to California. The survivors arrived in such bad condition that it took Esche months to nurse them back to good health. They carried salt across the mountains, but the strange, furry, long-legged creatures were not well received in Nevada.

  The silver miners can be added to a long list of novices who have found that camels, even the better-tempered Bactrians, can be disagreeable. They bite, spit, and kick. The miners hated them, as did their horses and mules, who became hysterical at the sight of them. This reaction by the other animals made the camels a public nuisance. A few would lope into town, and suddenly the street was alive with neighing, braying, and kicking. Virginia City, Nevada, passed an ordinance outlawing camels on the town streets except between midnight and dawn, when, presumably, the other animals were in stables resting. Eventually, to the relief of the miners, Esche gave up on the camels and released them in the Nevada desert to thrive on their own. Since no camel colony has ever been discovered there, it is assumed they all died, probably a slow, pitiful death.

  IN THE SPRING, seawater was pumped into the ponds of the south bay. Through the summer, the brine would be moved; by late summer, it was dense enough to crystallize. The brine turned pink and then a dark brick color. Today, when people fly into San Francisco, they sometimes gaze out the window and wonder about the pink-and-brown geometric ponds at the end of the bay.

  The color is a common phenomenon that had previously been observed in Europe, in the Dead Sea, and in China, among many other places that made sea salt. Both Strabo and Pliny wrote about this curious color in brine that later disappeared after crystallization. Strabo, who pondered the color of parts of the Red Sea, thought it was caused by either heat or a reflection.

  In Salt and Fishery, Discourse Thereof, Collins had mentioned the phenomenon, attributing the color to red sand. The red color was generally thought to be an impurity that could cause spoilage, and it was believed that it might turn the fish or meat red and then the food would soon spoil. In 1677, Anton van Leeuwenhoek, the Dutch naturalist who made numerous discoveries with a crude microscope, concluded that the red color was caused by microorganisms in the brine.

  Whatever the cause, the simple observable fact, as Denis Diderot pointed out in his eighteenth-century encyclopedia, is that “you know the salt is forming when the water turns red.”

  Charles Darwin observed the phenomenon in Patagonia:

  Parts of the lake seen from a short distance appeared of reddish color, and this perhaps was owing to some ifusorial animalcula. The mud in many places was thrown up by numbers of some kind of worm, or annelidous animal. How surprising it is that any creatures should be able to exist in brine.

  In 1906, E. C. Teodoresco identified a one-celled plant called dunaliella, which most observers concluded must actually be two species because the brine initially developed a green scum and only later, when more dense, turned red. Were there both green and red dunaliella? Darwin wrote of the complex ecology of sea saltworks where single-celled algae lived in brine and turned it green, but at a denser level, tiny shrimp and worms turned it red, and these reddish animals attracted flamingos, which turned pink from eating them. In fact, Darwin had figured out the entire mystery in the nineteenth century, but few listened to him until well into the twentieth century.

  The San Francisco Bay salt makers of the silver rush days believed the dark red color came from insects in the brine. Only in modern times has it been understood that dunaliella is green, but once the brine reaches a certain level of salinity, it turns red. In addition, tiny, barely visible shrimp, brine shrimp, live in the brine at this density. And there are also salt-loving bacteria of reddish hue that are attracted to brine. Not only does the red color signal that the brine is ready, it intensifies the solar heat and hastens evaporation, helping the salt to turn to crystals and fall out of the reddish water. Today, the saltworks of San Francisco Bay sell their reddish little creatures to other saltworks that wish to improve their evaporation process.

  Just as Diderot had observed but could not explain, when the brine reaches the density that attracts these shrimp, algae, and bacteria, it means that the brine is at a density close to the point of crystallization. The process of making salt, though practiced since ancient times, was beginning to be understood.

  PART THREE

  Sodium’s Perfect Marriage

  It is an old remark, that all arts and sciences have a mutual dependence upon each other. . . . Thus men, very different in genius and pursuits, become mutually subservient to each other; and a very useful kind of commerce is established by which the old arts are improved, and new ones daily invented.

  —William Brownrigg,

  The Art of Making

  Common Salt, London, 1748

  CHAPTER EIGHTEEN

  The Odium of Sodium

  EDMUND CLERIHEW BENTLEY, a British author of crime novels who lived from 1875 to 1956, wrote these lines, it is said, while in a chemistry class:

  Sir Humphry Davy

  Abominated gravy.

  He lived in odium

  Of having discovered sodium.

  This was the first of a verse type known as a clerihew, which is a pseudo-biographical verse of two rhymed couplets in which the subject’s name makes one of the rhymes. It became a genre of humorous poetry, although not many people can recite another example of a clerihew.

  Sir Humphry Davy was also an Englishman, born in 1778, and a largely self-taught chemist. When he was a twenty-year-old apprentice pharmacist in Cornwall, the Pneumatic Institution of Bristol offered him a job researching medical uses of gases, which may have been a twenty-year-old’s dream job. There is little evidence of his feelings about gravy, but he was known to have a great fondness for nitrous oxide, laughing gas, which he experimented with at length and found to be not only an enjoyable recreational drug but a cure for hang
overs. Notable friends, including the poets Robert Southey and Samuel Taylor Coleridge, shared in the experiments. But Davy learned that some gases are better than others, and he almost died from his experiments with carbon monoxide.

  Davy’s work in Bristol came under attack by conservative politicians, including the famous Irish MP Edmund Burke, who accused the gas experiments of promoting not only atheism but the French Revolution.

  Young Humphry Davy merrily mans the bellows in a laughing-gas experiment being presented by his predecessor at the Royal Institute, Benjamin Thomas, in a caricature by James Gellray. The Chemical Heritage Foundation, Philadelphia

  But within a few years, his other experiments with electrolysis, passing electricity through chemical compounds to break them down, earned him enduring fame. Davy’s chemistry lectures at the Royal Institute became so noted for the brilliance of his delivery that the talks were regarded as fashionable cultural events. Then, in 1812, to the disappointment of fans, he married a wealthy widow and gave up lecturing to spend his time touring Europe.

  Davy, a brilliant scientist, had a flair not only for performance and for living well, but also for self-promotion. He managed to garner credit for a phenomenal number of the scientific breakthroughs of his day. Through electrolysis, he was able to isolate for the first time a number of elements, including, in 1807, sodium, the seventh most common element on earth. This discovery was the first important step toward at last understanding the true nature of salt.

  THAT DIFFERENT TYPES of salt existed and were suited for different purposes was a very old idea. The ancient Egyptians knew the difference between sodium chloride and natron. But they didn’t understand their composition or how to make them. Saltpeter, which can be sodium nitrate or potassium nitrate, was well known by the medieval Chinese, who used it for gunpowder. After Europeans learned about gunpowder, the market for potassium nitrate seemed limitless. But little was known about its properties.

  As early as the sixteenth century, nitrates were used in cured meats to make them a reddish color, that was thought to be more in keeping with the natural color of meat. In fifteenth-century Poland, game was preserved in nitrate simply by gutting the animal and rubbing the cavity with a blend of salt and gunpowder, which was potassium nitrate. It took centuries of use before anyone understood how potassium nitrate and its cheaper cousin, sodium nitrate, which is often called Chile saltpeter, are broken down by bacteria during the curing of meat. The nitrate turns to nitrite, which reacts with a protein in the meat called myoglobin, producing a pinkish color. The reaction also produces minuscule amounts of something called nitrosamines, which may be cancer-causing. Today, the amount of nitrates is limited by law to what seems to have been deemed an acceptable risk for the oddly unquestioned goal of making ham reddish.

  For centuries, different types of salts were recognized by taste. The Great Salt Lake was clearly a concentration of sodium chloride because it had a pleasant salty taste, whereas the “bitter nauseous” taste of the Dead Sea indicated magnesium chloride. The long practiced principle of evaporating brine was that when brine becomes supersaturated—when it is at least 26 percent salt, which is considerably more than the 2.5 or 3 percent salt of seawater—sodium chloride crystalizes and falls out, or precipitates, from the liquid. But slowly it was discovered that after the sodium chloride, the salt of primary interest, precipitates, a variety of other salts crystalize at even denser saturation.

  In 1678, Dr. Thomas Rastel of Droitwich wrote:

  Besides the white salt above spoken of we have another sort called clod salt, which adheres to the bottom of the vats and which after the white salt is laded out, is digged up with a steel picker. This is the strongest salt I have seen and is most used for salting bacon, and neat’s [ox] toungues: it makes the bacon redder than other salt, and makes the fat meat firm.

  THE WORD CHEMISTRY was first used in the early 1600s, although the science was not considered an independent field of research until the end of the century. One of the accomplishments of early chemists had been to identify some of the salts that precipitated out of brine. But despite this work, it seems that very few people in the seventeenth century had any idea what a salt was.

  A 1636 book by Bernard Palissy, with the dreamy title How to Become Rich and the True Way in Which Every Man in France Could Grow and Multiply Their Treasury and Possessions, states that “sugar is a salt.” In listing all the “various salts,” Palissy includes “grape salt, which gives taste and flavor to wine.” It is not surprising that he concluded that it was impossible to list all the salts. In John Evelyn’s 1699 discourse on salads, he states that sugar is sometimes referred to as “Indian salt.”

  Apparently, there was little definition of salt other than as something made of white crystals. This began to change in the early seventeenth century, when Johann Rudolf Glauber, a German chemist, took a cure in a spring near Vienna and extracted from the water a salt that he called sal mirabile. The salt was hydrated sodium sulphate, though Glauber could not have put it that way, because Davy had not yet discovered sodium. Glauber sold his discovery as a secret cure, a mineral bath of allegedly wondrous health benefits. It became so famous that today, though it is more used in metallurgy, textiles, and other industries than as a bath salt, it is still commonly known as Glauber’s salt. Enough of an entrepreneur to keep his formula secret, Glauber was also enough of a scientist to reveal, after his fortune was made, that when sulphuric acid was applied to common salt, producing hydrochloric acid, a process that had already been well known for centuries, the residue, that had always been thrown out, was Glauber’s salt.

  Later in the same century, Nehemiah Grew, a British plant physiologist who is credited with being the first human ever to witness and document plants having sex, studied the celebrated health spring water of Epsom in Surrey, England. He isolated a salt, magnesium sulphate, ever after known as Epsom salt. Epsom salt is now used not only medicinally but in the textile industry, for explosives, in match heads, and in fireproofing.

  But Nehemiah Grew was even less forthcoming than Glauber about his discovery. Only after years of speculation was it discovered by chemist Caspar Neuman in 1715 that Epsom salt could be made by applying sulphuric acid to the mother liquor.

  Mother liquor is the dark blood-red water that remains after common salt precipitates out of brine. An eighteenth-century London chemist named John Brown discovered that Epsom salt could be boiled out of the mother liquor without sulphuric acid. Brown also found another salt in the liquid. The study of this third salt, now known to be magnesium chloride, unleashed a chain of discoveries, including Davy’s 1808 announcement that he had found a new element, magnesium. In 1828, Antoine Bussy isolated workable quantities of the metal, and an industry was born. Magnesium is used to prevent corrosion of steel and in explosives, lightbulbs, and lightweight metal alloys.

  At the time of Neuman’s early-eighteenth-century experiments with mother liquor, the liquid was called bittern, and salt makers usually threw it away or fed it to animals or even poor people as a cheap source of salt. The Dutch found that it worked well for washing windows. Despite pleas from scientists, most saltworks continued to throw out their leftover bittern.

  Then, in 1792, sodium carbonate, soda, was made from mother liquor. Soda found in nature had been used since ancient times in early industries such as glassmaking. Natron is a form of soda. In fact, Davy named sodium after soda because it was one of the element’s best known compounds. The manufacture of artificial soda started numerous industries. Sodium hydrogen carbonate, bicarbonate of soda, is used in food as well as for glassmaking and textiles. Sodium carbonate is used in making paper, plastics, detergents, and the artificial fabric rayon.

  By the time of the Civil War, commercially made soda was common, and soda fountains had already become widespread in America. A popular American women’s magazine gave a recipe for making carbonated drinks.

  Put into a tumbler lemon, raspberry, strawberry, pineapple or any other a
cid syrup, sufficient in quantity to flavor the beverage very highly. Then pour in very cold ice-water till the glass is half full. Add half a teaspoonful of bicarbonate of soda (to be obtained at the druggist’s) and stir it well in with a teaspoon. It will foam up immediately, and must be drank during the effervescence.

  By keeping the syrup and the carbonate of soda in the house, and mixing them as above with ice-water you can at any time have a glass of this very pleasant drink; precisely similar to that which you get at the shops. The cost will be infinitely less.—Godey’s Lady’s Book, 1860

  For many centuries there had been a great confusion between potash and soda. The name potash is derived from the process used for making potassium carbonate, cooking down water and wood ash in earthen pots. Like soda, potash had many industrial applications long before it was chemically understood. Among other things, it was used in making glass and soap.

  Before sodium carbonate in the form of baking soda was manufactured, potash was used in baking. Amelia Simmon’s cookbook, originally published in Hartford and then Albany in 1796, is considered the first American cookbook not only because it was published after the Revolution, but because it was written by an American, for Americans. Simmons used enormous quantities for apparently huge cakes. One recipe, for “Independence cake,” called for twenty pounds of flour, fifteen pounds of sugar, ten pounds of butter, and twenty-four eggs. Many of her baking recipes called for “pearl-ash,” which was potash, as a rising agent.