Chapter 24. Solvay (Ammonia)


The greater part of the soda now employed is obtained by Leblanc's process, which while it admits of lixiviating the soda readily and completely, is defective, inasmuch as the residue, or waste as it is technically called, contains nearly all the sulphur used in the manufacture; and that this is not a slight loss may be inferred from Oppenheim's statement, that in the alkali works at Dieuze, Lorraine, the accumulated waste contains an amount of sulfur valued at 150,000. For every ton of alkali made there is accumulated 1 tons of waste, containing 80 per cent. of the sulphur used in the manufacture; and this waste, until lately thrown on a refuse heap in some fields adjacent to the works, often proved a nuisance in hot weather, giving rise to fumes of suphuretted hydrogen.

 Wagner's Chemical Technology, 1872 AD [1]


Four score and seven years ago our fathers brought forth on the European continent, a new industry, conceived in Liberty, and dedicated to the proposition that all men are created equal. The chemical revolution begun by Leblanc in 1790 had passed from France to Britain, where the repeal of the salt tax had stimulated the growth of a booming soda industry. This industry used as raw materials, salt, sulfur, limestone, saltpeter, coal, air, and water; its products were the alkalis, sodium carbonate and sodium hydroxide. Cheap alkalis brought to the ordinary citizen those luxuries which had formerly been enjoyed only by the rich and powerful: glass for bringing light into dark places, paper for bringing the printed word into proletarian homes, and soap for bringing sanitation into cities oppressed by filth and disease. And while the Leblanc process delivered on many of the promises of the revolution, you may very well wonder why the world has little noted, nor long remembered the work which it so nobly advanced. I will tell you.

You will, of course, recall that in addition to valuable alkalis, the Leblanc process produced two waste products, hydrogen chloride and calcium sulfide. Acidic hydrogen chloride gas was sent up the chimney, after which it decimated vegetation in the vicinity of an alkali works. Insoluble calcium sulfide was conveniently disposed of in heaps where the vegetation used to be. Unfortunately, when calcium sulfide reacts with rain water it farts out noxious hydrogen sulfide, a gas which will never have a rose named after it. Not surprisingly, there was little demand for posh plant-side homes in the neighborhood of the Widnes Alkali Works.

As a consequence, alkali manufacturers became popular targets for lawsuits and government regulations. The British Alkali Act of 1863, for example, required the absorption of 95% of the hydrogen chloride produced by the salt cake furnace.[2] This was easily accomplished, hydrogen chloride being quite soluble in water; the waste gas was sent up through a stone tower filled with coke; water dribbling down through the tower absorbed the hydrogen chloride, producing aqueous hydrochloric acid. Voila! Clean air. There being little demand for hydrochloric acid, however, it was natural to dispose of it in the nearest river, a loophole closed by the Alkali Act of 1874.

In addition to hydrogen chloride, calcium sulfide was a thorn in the side of soda manufacturers. While the community complained about stinking heaps of tank waste, the manufacturers themselves mourned the loss of valuable sulfur. Sulfur was then imported almost exclusively from Sicily and a monopoly established there in 1838 increased prices sharply.[3] An alternative to sulfur was found in sulfur dioxide, roasted from British and Spanish pyrites, but there was no getting around the stubborn fact that every ounce of sulfur procured from whatever source was destined to wind up as calcium sulfide waste. The one silver lining of the calcium sulfide cloud was that it could be converted into sodium thiosulfate, used by photographers to fix photographs. Even so, the demand for photographic fixer was dwarfed by the supply of tank waste; the noxious heaps became mountains, testing whether any industry so conceived could long endure.

It was into such a world that I, Ernest Solvay, was born in 1838. Son of a Belgian salt-maker, I cut my teeth on salt and at the age of 21 went to work for my uncle, who managed a coal-gas plant. Growing up as I did surrounded by salt, coal, gas, and ammonia, it was natural that I should apply my little gray cells to the problems of the soda industry. Many commercial enterprises had attempted to exploit the reaction of salt, ammonia, and carbon dioxide to produce ammonium chloride and sodium carbonate. But if the ammonia were not recovered, the process would suffer from the waste of ammonia, as the Leblanc process had from the waste of sulfur. To this end, I devised a recovery process using lime to liberate ammonia gas from ammonium chloride. I realized, however, that winning this battle would not be enough to win the war.

Ward and Roebuck, after all, had brought the chamber acid industry into being, but had failed to keep their secrets. Leblanc himself had given birth to the soda industry and yet political upheaval had robbed him of the fruits of his labors. Since it is not in the interest of secrets to be kept, I was careful to patent my ideas both in Belgium and in Britain. I then established a soda works in Belgium which began production in 1864. While the construction of a Solvay plant was more expensive than a comparable Leblanc plant, it required fewer raw materials; thus capital investment was higher but operating costs were lower. I built a second plant in France, but the real key to my commercial success was the sale of licenses abroad; my particular un-kept secrets were going to pay as they went. Solvay plants were established by Brunner, Mond & Co. in Britain and by Solvay Process Co. in the United States, paying royalties on every ton of soda produced.

The established alkali manufacturers were not about to surrender without a fight, however. In 1868 Henry Deacon introduced a process for turning waste hydrogen chloride into bleaching powder, which found a ready market in paper and textiles.[4] In 1887 Alexander Chance finally succeeded where so many others had failed in recovering sulfur from tank waste. But these piece-meal improvements would make a patchwork of existing alkali plants, sacrificing simplicity for efficiency. With lower operating costs, I was able to drop the price of soda to the point that my competitors were forced to sell it at a loss. Leblanc soda works, in an ironic twist, would be kept afloat only by sales of bleaching powder produced from acid formerly run to waste.

World production of soda in 1863 had been 150,000 tons, all produced in Leblanc plants. By 1902 world production of soda would soar to 1,760,000 tons, over 90% of which would be produced in Solvay plants.[5] It would be altogether fitting and proper to celebrate the victory of cleaner and more efficient processes over those crippled by pollution and waste. But, in a larger sense, we can not dismiss—we can not forget—we can not overlook those who struggled to bring light, literature, and lather to all peoples. It is rather for us to be here dedicated to the great task remaining before us—that from these honored dead we take increased devotion to that cause for which they gave the last full measure of devotion.



Reference [29], pp. 184-185.


Reference [68], p. 89.


Reference [75], p.33.


Reference [60], pp. 95-98.


Reference [52], p. 59.