The Proper Chemistry: Madder root, Turkey purple oil and artificial detergents

This is some chemistry historical past to consider subsequent time you do your laundry.


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What an odd time period: “Turkey purple oil.” It has nothing to do with fowl. It owes its title to a reference to the dye generally known as “Turkey purple,” which in flip is called after the nation of Turkey from the place it was first imported into Europe across the 18th century. The supply of the dye is the foundation of the madder plant, Rubia tinctorum, which was cultivated in China, India and Egypt lengthy earlier than Turkey existed as a rustic. Fabric dyed with madder was recovered by archeologists exploring the traditional metropolis of Mohenjo-daro, based round 2500 BC, now in Pakistan, and was additionally discovered within the tomb of Tutankhamun.

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Varied strategies of manufacturing fabric dyed purple with madder have been handed down by means of historical past, with a number of curious steps concerned. It begins with steeping the material in rancid olive oil, soda ash and sheep dung, then treating it with alum, and eventually dyeing in vats of madder extract and bullock’s blood. Precisely which of those substances have been important was contentious, however the olive oil and soda ash have been seemingly useful as a result of they react to provide cleaning soap. With regards to dyeing, it is necessary that materials comprise no greasy residues that forestall the dye from adhering.

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A serious step ahead was taken in 1831, when French chemist Edmond Frémy reacted olive oil with sulphuric acid. Upon neutralizing the answer with lye, he obtained a liquid with a soapy really feel that lathered when blended with water. He didn’t understand it, however he had really made the world’s first artificial detergent. Not like cleaning soap, it didn’t react with calcium or magnesium in water to provide an insoluble scum that was the bane of dyers.

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This sulphated olive oil turned out to be adept at eradicating grease from fabric and, as is commonly the case with science, spurred efforts to search out “new and improved” variations. Varied animal fat and plant oils have been reacted with sulphuric acid with the oil extracted from castor beans proving to be particularly helpful. Sulphated castor oil was nice for treating fabric previous to dyeing, significantly with Turkey purple. It was christened “Turkey purple oil” and was embraced by European dyers. However their pleasure didn’t final very lengthy.

In 1869, German chemists Carl Graebe and Carl Liebermann, working for the chemical firm BASF, and English chemist William Henry Perkin independently discovered a option to synthesize alizarin, the purple part of madder root, from anthracene extracted from coal tar. This made Turkey purple the primary pure dye to be duplicated synthetically. In consequence, the madder trade, estimated to be price about $16 million a yr, an astounding quantity on the time, collapsed virtually in a single day. Artificial alizarin was cheaper and simpler to make use of. However finally, it, too, was changed by extra light-resistant quinacridone pigments developed by DuPont in 1958.

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The downfall of the madder trade didn’t spell the top for Turkey purple oil because it was nonetheless efficient for treating fabric earlier than dying with artificial alizarin. Right this moment, it’s used as a dyeing assistant, an emulsifier in cosmetics, and in aromatherapy merchandise the place dispersion of important oils in water is vital. However what’s of larger curiosity, is the position Turkey purple oil was destined to play within the creation of the fashionable detergent trade, though in a round-about means.

Till the Thirties, laundry merchandise have been primarily based on cleaning soap. Firms akin to Procter & Gamble, Lever Brothers and Colgate-Palmolive have been main producers however have been saddled with an issue. Cleaning soap labored properly in “comfortable” water with a low mineral content material, however in “arduous” water it reacted with calcium and magnesium to provide a precipitate that might deposit on garments. Easy methods to clear up this downside? A clue started to emerge in Germany through the First World Warfare when fat to make cleaning soap have been briefly provide as a result of they have been wanted to provide lubricants and glycerol for nitroglycerine. Options for cleansing have been wanted, and the I.G. Farben Firm turned to ox bile, since this fluid, produced within the liver, was identified to help digestion by breaking down fat, very similar to cleaning soap. Bile didn’t grow to be an excellent cleansing agent, nevertheless it did show to be helpful within the textile trade as a “wetting agent,” permitting a dye resolution to penetrate materials.

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Given the dimensions of the textile trade, Igepon, because the product was marketed, stirred up competitors. The Deutsche Hydrierwerke Firm, aiming for an “improved” model, now harkened again to Turkey purple oil. Like Igepon, it was not an excellent cleaner, however was additionally unaffected by arduous water. As an alternative of utilizing ricinoleic acid from castor oil, the corporate’s chemists turned to reacting lauric acid from palm kernel or coconut oil with sulphuric acid. Certainly, the sodium lauryl sulphate produced turned out to be wonderful agent for treating textiles earlier than dyeing and was not bothered by arduous water. The corporate, nonetheless, by no means considered utilizing it as a detergent for dwelling use as a result of it was not within the laundry product enterprise.

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As luck would have it, Robert Duncan, a course of engineer with Procter & Gamble, was visiting German chemical crops in 1931 to see in the event that they have been concerned in any analysis probably helpful for his firm. He heard concerning the sodium lauryl sulphate (SLS) story and was intrigued by the substance’s immunity to arduous water provided that scum was a serious downside with P&Gs cleaning soap merchandise. He bought 100 kg and had it shipped again to Cincinnati.

Inside a few years, P&G chemists confirmed that SLS labored properly in arduous water and Dreft, the primary industrial artificial laundry detergent, appeared available on the market. It was solely reasonably profitable as a result of it didn’t work properly on closely dirty garments. Clearly “new and improved” variations have been wanted. Dogged work by chemist David Byerly, code -named “undertaking X,” resulted in enormously improved cleansing effectivity with the addition of sodium tripolyphosphate, and Tide was born. Many enhancements within the formulation have been made since then, however it’s fascinating to notice that it was Turkey purple oil that turned the tide when it got here to the introduction of the artificial detergents we drop in our washing machines with out a lot thought as to their origin.

Joe Schwarcz is director of McGill College’s Workplace for Science & Society ( He hosts The Dr. Joe Present on CJAD Radio 800 AM each Sunday from 3 to 4 p.m.

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