Chlorine: From toxic chemical to household cleaner

Hello again! Here's yet another interesting article I found. This time it is about one of the most common chemicals around us. It is massively used for cleaning and disinfection. We can say that we have mastered the beast, because it is a very dangerous chemical. However, we use it every day.

This article is as dense as it is interesting. So I split it in paragraphs for easier digestion.

This is the link to the original article, in case you want to read it directly:

http://www.bbc.com/news/magazine-27057547

BBC News Magazine 18 April 2014 Last updated at 23:26 GMT

Chlorine: From toxic chemical to household cleaner

By Justin Rowlatt BBC World Service

Few chemicals are as familiar as table salt. The white crystals are the most common food seasoning in the world and an essential part of the human diet. Sodium chloride is chemically very stable - but split it into its constituent elements and you release the chemical equivalent of demons. The process is brutal. Vast amounts of electricity are used to tear apart the sodium and chlorine atoms in salt molecules through the process of electrolysis. It happens at vast industrial sites known as chlor-alkali plants, the biggest of which can use as much electricity as a small country. Which is why the price of both chlorine and sodium tend to track the price of electricity very closely. It also explains why Industrial Chemicals Ltd's chlor-alkali plant in Thurrock, Essex, is right next to an electricity substation.

1. Seasoning: products like spices, used to improve or change the flavour and taste of some food. 
2. Constituent elements: the parts of something.
3. vast amounts: very big quantities
4. tear apart: to separate by breaking something which is very strongly connected. For example a piece of cloth, paper, cardboard or meat (for example a roast chicken leg).
5. right next: immediately next to something, very very close.

David Compton, ICL's chief chemist, shows me a huge mound of pure white salt. It comes, he tells me, from the rock salt deposits buried under Cheshire, in the north of England, a resource that was first mined by the Romans. And it's at least as pure, he says, as the salt you sprinkle on your dinner. It is mixed with water in huge basins to make a concentrated brine, which is pumped into a big industrial barn that contains what looks like a giant chemistry set. A series of huge tanks are connected by a web of pipes painted in different colours, all leading back to a big black tank. This is the business end of the process, the electrolyser. It exploits an equivalence between chemistry and electricity that was first codified by Michael Faraday.

1. mound: an accumulation of something like salt, sugar, sand...
2. buried: kept under the surface, for example, dead people in a cemetery.
3. resource: something needed to do something else. For example oil, wood, gas...
4. sprinkle: to distribute something in a way that it will not be concentrated, for example salt over a piece of meat. In many office buildings there are sprinklers on the ceiling, which spray water in case of fire. 
5. basin: a container for liquids which is open at the top. For example, in a bathroom you have a washbasin, at which you brush your teeth, wash your face and your hands.
6. brine: water with a very high concentration of salt. Often used in the past as a preservative for foods such as meat, fish or others.
7. barn: a storage building in a farm, where food for the animals or farming equipment are stored.
8. to exploit: to use something to your advantage.

Sodium and chlorine are both highly reactive - bring them into contact with each other and an electron passes between them, gluing them together to become salt. Reverse the process - by creating an enormous electrical current in the opposite direction - and you can split them apart again.

Inside the electrolyser, the brine is fed into a series of cells each separated by a membrane. Chlorine gas is produced at one electrode, and hydrogen gas - split off from the water molecules in the brine - at the other, leaving behind a solution of sodium hydroxide, also known as caustic soda. Until fairly recently the process used mercury as one of the electrodes. This produced chlorine-free sodium hydroxide, but released tiny traces of mercury, which is very toxic, into the environment. So mercury cells are gradually being phased out around the world.

1. to glue: to put to things together so they will not separate, by using glue (e.g. "Loctite")
2. by: this preposition introduces some instrumental meaning. e.g. if you travel by car, it means you use the car to carry yourself from one place to another. 
3. split them apart: to split means to break. to split apart means to break and separate.
4. brine is fed: (see brine above). to feed means to introduce some material (solid or liquid) into a system. This includes food and drink in animals and people. You can also use it with things, such as "I fed the printer more paper".
5. split off: same meaning as split apart. Off means separation or disconnection. 
6. tiny traces: very small quantities.
7. to phase out: to gradually stop producing or using some product. For example mercury-cadmium batteries or CFC gases have been phased out. 

Inside ICL's laboratory, Andrea Sella, professor of chemistry at University College London, hands me a fragile-looking glass balloon. It is an evil-looking greenish-yellow colour. "That's chlorine," says Professor Sella, with a wicked grin, "one of the most ferociously aggressive materials out there." I grasp the bulb of lethal gas more carefully. Andrea describes chlorine as aggressive because it is very reactive. That makes it extremely useful, but also very dangerous. It takes its name from its sickly colour - chloros is the Greek word for green. As all chemists know, you need to be very careful with chlorine. Its reactivity makes it very toxic. If you inhale chlorine, it reacts with the water in your lungs, converting it into powerful acids.

1. evil-looking: if something is evil it might have a negative effect or intention. Something evil-looking is something whose image gives you that impression.
2. wicked: a wicked person is a very bad person. 
3. grin: a face gesture between a laugh and a smile.
4. to grasp: to hold something. Metaphorically you can grasp concepts or ideas.
5. sickly: something with the appearance of being sick or causing sickness.
6. inhale: to absorb through the nose or mouth some gas or smoke. The opposite is to exhale. 

The effects can be horrific, as the World War One poet, Wilfred Owen, witnessed first-hand. "Dim, through the misty panes and thick green light, As under a green sea, I saw him drowning. In all my dreams, before my helpless sight, He plunges at me, guttering, choking, drowning."

1. dim: if something is dim, it means it is difficult to see clearly, for example if there is a lot of smoke. If light is dim, it means it is not strong enough to help you see clearly. If you ask someone to dim the lights, it is because they are to intense for you. Finally if you say someone is dim, it means their intelligence is limited.
2. misty: as if you see something through the mist. So not very clear or defined. If someone has misty eyes it is because they are full of tears.
3. panes: each section of glass in a window.
4. to plunge: to throw something or someone (including yourself) into some liquid or substance. e.g. As soon as I arrived home, I changed into my swimsuit and plunged into the swimming pool.
5. to gutter: to cry tears so they make gutters (channels) down your face.
6. to choke: to have difficulty breathing because something is in your mouth or throat.
7. to drown: to die of asfixiation caused by a liquid. e.g. he could not swim, so he drowned in the river.

In his poem Dulce et Decorum Est, Owen describes the effects of the deadly chlorine gas used by both the German and British armies during World War I. It was particularly effective as a chemical weapon because it is heavier than air and, on still days, would collect in the trenches. "Drowning" very accurately describes what happened to soldiers who were exposed to the gas. Their bodies responded to the irritation caused by the acid by filling their lungs with liquid. Many died from suffocation.

1. deadly: something that can kill you
2. still days: days when the wind doesn't blow.
3. accurately: with precision.
4. suffocation: not being able to breathe.

But while chlorine may have been put to some dastardly uses over the centuries, its reactivity has also been incredibly useful to humanity. It means chlorine is relatively easy to incorporate into other materials and often makes compounds more stable. "That's because," says Andrea with relish, "chlorine hangs on like grim death to the atoms it bonds with." One of the best examples is polyvinylchloride, or PVC, which consumes a third of chlorine. This incredibly versatile and durable plastic celebrated its centenary last year. PVC crops up everywhere - packaging, signage, old-fashioned vinyl records, the leatherette effect of many car seats.

1. dastardly: intentionally bad or cruel. (in my opinion, very unusual, literary word)
2. relish: pleasure, enjoyment
3. hang on like grim death:ok let's go one word at a time: a) hang on: to continue hanging, to insist on hanging from something. grim: sad, sinister. So to hang on like grim death means that something sticks to you so strongly that you can compare it with death (because death hangs to you forever... ) In Spanish you would say something like "hang on like a piece of chewing gum in your hair".
4. to bond: to connect in a solid way. 

But it is the construction industry that is by far the biggest end-user of this plastic. Over 70% of PVC ends up in everything from drainpipes to vinyl floors, roofing products to double-glazed window-frames. "We call it the construction polymer," says Mike Smith, chlorine market expert at the consultancy IHS. "Chlorine also goes into construction in other forms," he adds. "Polyurethane, which is a great insulation material." And that has the odd consequence that the demand for chlorine rises and falls in line with property booms and busts.

1. by far: this means there is a very big, clear difference between two things. So it is not only the biggest user, but the second is very clearly below. 
2. end-user: final user in a production chain. This expression appears a lot in software products. (End-user agreement.)
3. drainpipes: pipes (conducts) used to evacuate liquids from places, for example a roof or a kitchen sink. If they are open they can be called gutter (see gutter as a verb above).
4. double-glazed window: a window which has two layers of glass to offer protection against temperature changes.
5. insulation: double glazing is an insulation system. Insulation is protection against factors such as noise, heat, cold, humidity...
6. odd: strange, unusual.
7. in line: in parallell, at the same time.

And because the supply of sodium is inextricably tied to that of chlorine, it has an even odder consequence. A collapse in the housing market - as Spain suffered in recent years - can make it more expensive to manufacture staple products like soap and paper, which rely on sodium. But PVC is just one of chlorine's many industrial applications. Chlorine is one of the most versatile and widely used industrial chemicals. "It is a real workhorse," says Mike Smith, adding that much of the chemical industry would be impossible without it. Something like 15,000 different chlorine compounds are used in industry, including the vast majority of pharmaceuticals and agricultural chemicals.

Often chlorine is used during the production process and doesn't actually turn up in the final product. That's true of the production of two vital elements. From a battered cardboard box Andrea produces a cylinder 15cm long and 3cm wide, encrusted with crystals of a beautiful silver-coloured metal. It is, he tells me, titanium. Titanium is the basis of much of the paint industry. It is used in hi-tech alloys for aircraft and bicycles as well as in dental implants and chlorine is an indispensable part of the purification process. Similarly the incredibly high-purity silicon essential for the production of computer chips and solar panels is only possible thanks to a process that uses chlorine.

1. staple products: basic products used by the vast majority of the population, such as soap, paper, milk, bread, eggs...
2. workhorse: something or someone who will do a lot of heavy-work.
3. to turn up: to appear, to be present.
4. alloy: a mix of metals, for example, steel is an alloy of iron with different proportions of other metals.

But it was chlorine's cleansing power that led to the first commercial applications of the element. Its efficacy as a disinfectant was discovered thanks to an early 19th Century effort to clean up the gut factories of Paris. The "boyauderies" processed animal intestines to make, among other things, strings for musical instruments. A French chemist and pharmacist called Antoine-Germain Labarraque discovered that newly-discovered chlorinated bleaching solutions not only got rid of the smell of putrefaction but actually slowed down the putrefaction process itself. Within a few decades chlorine compounds were being used to disinfect everything from hospitals to cattle sheds as well as to treat infected wounds in patients. Chlorine is credited with deodorizing the Latin Quarter of Paris, until then infamous for its terrible stench.

1. cleansing: to clean or purify.
2. to clean up: to clean something completely.
3. gut factories: guts are things such as the intestines. These factories make their products with the intestines of animals.
4. newly discovered: discovered recently.
5. cattle-sheds: small buildings, usually made of wood, where you keep cattle. There are other kinds of sheds, like the garden shed, which many people have and where you keep your gardening tools.
6. to be credited with: what happens when someone recognizes you did something, usually good things. 
7. infamous for: the opposite of famous for. Being famous for a negative thing.
8. stench: a very penetrating smell, like food in bad condition, or something putrid.

The early advocates of chlorine did not know how chlorine worked, they just knew that it helped clear the "miasmas" thought to spread contagion. It would be half a century before the microbes that chlorine destroys would be identified. Chlorine is used around the world to treat water to ensure it is safe to drink. It is the basis of many disinfectants and a key ingredient of the bleach you use to clean surfaces in your home and to purge any microbes from your toilet bowl.

It is also used to keep swimming pools free of bacteria, hence the distinctive smell. But here's something you probably didn't know, and if you are a regular swimmer, may not wish to know. That smell isn't chlorine, at least not the element. It is actually a chlorine compound called chloramine, which is created when chlorine combines with organic substances in the water. So what are those organic substances? We are talking about sweat and urine. So if you've ever noticed that the "chlorine" smell is stronger when the pool is full of kids, well now you know why.

1. advocate: someone who defends an idea or a cause. Not to be confused with "abogado" which is to be translated as lawyer, attorney, barrister and others...
2. bleach: cleaning liquid extensively used to clean and disinfect floors and other elements. It's main element is chlorine. It is also used to make clothes white, so the process of making something white by using bleach is "to bleach". This verb is also used for intense hair lightening processes. 
3. toilet bowl: an element in the bathroom where you sit and... do I need to explain more?
4. hence: therefore, for that reason
5. sweat: liquid coming out of your skin pores when it is very hot or you are performing some intense activity.
6. urine: waste liquid from the body that usually goes into the toilet.

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