BLEACHING POWDER WAS NO MATCH FOR THE ‘GREAT STINK’ OF LONDON
MPs tried to counter stench coming from the Thames in sweltering summer of 1858
It was during the summer of 1858 that Londoners experienced the “Great Stink.” The city was sweltering with temperatures that reached 36 C, but it was not the heat that bothered people.
It was what the heat did to the human waste that had been accumulating on the banks of the Thames. The rising temperature had increased the microbial activity in the fecal matter causing the release of putrid smelling compounds like indole, skatole, methanethiol, dimethylsulphide and hydrogen sulphide, the classic odour of rotten eggs. The stench in the city was overwhelming and within the House of Parliament the smell was so bad that members walked around clutching handkerchiefs to their nose.
An attempt was made to remedy the problem by saturating the window curtains with calcium hypochlorite, known at the time as “chloride of lime” or “bleaching powder.”
When dissolved in water, calcium hypochlorite forms hypochlorous acid, a strong oxidizing agent. Oxidizing agents have an appetite for electrons and look to steal them from other molecules.
Since electrons are the essence of chemical bonds, the result of oxidation is the alteration of the molecular structure of the substance being oxidized. In this case, the malodorous compounds are converted into less odorous ones.
Calcium hypochlorite is also a strong disinfectant, meaning that it can destroy bacteria, including those that convert fecal components like sulphates into hydrogen sulphide and methionine, a component of proteins, into stinky mercaptans. That explains why bleaching powder was a component of one of the most widely used antiseptic solutions in the First World War. Developed by a team of pathologists at the University of Edinburgh, it was known as “eusol,” an acronym for “Edinburgh University Solution of Lime.” That, though, wasn’t the first time the powder was used to control disease. Back in 1846, the Hungarian physician Ignaz Semmelweis had stamped out an epidemic of childbed fever with it.
Bleaching powder is made by reacting calcium hydroxide, or lime, with chlorine gas in a process that was developed over 200 years ago by Scottish chemists Charles Tennant and Charles Macintosh.
The latter became a household name because of an unrelated invention, the sandwiching of a layer of rubber between two sheets of fabric to produce a water-resistant material. Raincoats made of this novel fabric were christened “Macintoshes.”
While bleaching powder can indeed serve as deodorizing substance, it was too weak in the face of the Big Stink. The nasally tortured Members of Parliament decided that something had to be done, and finally allocated funds to start the construction of a new sewer system that would transport the ever-increasing amount of human waste to a point in the Thames downstream from London. The massive project under the guidance of civil engineer Joseph Bazalgette took 15 years and involved building three massive embankments on the shores of the Thames to house the sewer tunnels.
Sewer systems had existed before in London, but they were primitive pipes that emptied into cesspools or into Thames in the middle of the city. Even before the “Great Stink,” there had been much talk about a need to clean up the river, a problem that famed scientist Michael Faraday highlighted with an article in the Times in which he described dropping pieces of white paper into the river and seeing them disappear as soon as they hit the murky water.
The worry was that the dirty water emitted contaminated air, or “miasma,” that spread diseases like cholera. This was not the case, but the smelly water was indeed responsible for disease when it was ingested.
Physician John Snow had already noted during a cholera outbreak in 1853-54 that the incidence of cholera was especially high in the vicinity of Broad Street, where people relied on a pump for their water.
Snow thought the water was contaminated and even suggested the handle of the pump be removed to curb the epidemic.
Water-borne disease finally began to be controlled at the end of the 19th century with the introduction of water disinfection. Once again, bleaching powder came to the fore. In 1897, a typhoid epidemic broke out in Maidstone, England and Dr. Sims Woodhead suggested its use to treat the town’s drinking water, which was done, but not without opposition. People did not want chemicals added to their water! It took another 18 years before chlorination was accepted as being helpful in controlling water-borne disease, with London finally adding bleaching powder to Thames water before it was routed into the city’s main aqueduct for drinking water.
Unfortunately, today there are still some two billion people who do not have access to safe water. As a result, hundreds of thousands die every year from cholera, dysentery, typhoid and polio due to drinking water contaminated with feces. And that really stinks. joe.schwarcz@mcgill.ca Joe Schwarcz is director of McGill University’s Office for Science & Society (mcgill.ca/oss). He hosts The Dr. Joe Show on CJAD Radio 800 AM every Sunday from 3 to 4 p.m.