How Bleach Works: Disinfection, Stain Removal and Dangers

To bleach is to remove colour by exposure to sunlight or by a chemical process. Some types of  bleach can also destroy germs.
To bleach is to remove colour by exposure to sunlight or by a chemical process. Some types of bleach can also destroy germs. | Source

A Versatile Household Product

Bleach is an amazing, multipurpose product that is very useful in homes, hospitals, science laboratories and industry. It's a potent germ killer that can also whiten and brighten fabrics and remove stains. Some people even use bleach to create special effects in their art projects.

There are several chemicals that can act as bleaches. The most common is sodium hypochlorite, or NaOCl. (The formula is also written as NaClO.) Sodium hypochlorite dissolved in water is sometimes known as chlorine bleach. It destroys a wide range of bacteria, algae, fungi and viruses.

Other hypochlorites can also act as bleaches, including calcium hypochlorite. This is sold as "bleaching powder". Some chemicals that don't belong to the hypochlorite family are bleaches too, such as hydrogen peroxide and sodium perborate. This article is concerned with sodium hypochlorite bleach, however, which is easily obtainable and widely used. It's a very helpful product, but it must be used with caution since it's potentially dangerous.

Ultraviolet light from the sun can act as a bleach.
Ultraviolet light from the sun can act as a bleach. | Source

The History of Bleaches

The discovery that sunlight can bleach fabrics is a very ancient one. The ultraviolet radiation in sunlight is responsible for the colour fading action. Like chemical bleaches, UV light also kills germs if it's sufficiently intense.

The discovery of chemical bleaches was based on the work of three scientists in the eighteenth and nineteenth centuries.

  • A Swedish scientist named Carl Wilhelm Scheele discovered chlorine. (This is significant because sodium hypochlorite contains chlorine.)
  • A French scientist named Claude Berthollet discovered that chlorine could bleach fabrics. He was also the first person to make a solution of sodium hypochlorite, which he called "Eau de Javel" or Javel water. The name came from the part of Paris in which Berthollet worked.
  • Antoine Germain Labarraque, another French scientist, discovered that hypochlorites could act as disinfectants.

Laundry bleach brightens white fabrics.
Laundry bleach brightens white fabrics. | Source

Sodium Hypochlorite

Sodium hypochlorite is a white powder in its pure form. The bleach that is bought in stores contains sodium hypochlorite dissolved in water. It's a clear solution with a slightly yellow color. Household bleach that is intended to be used for disinfection generally contains about 5.25% sodium hypochlorite by weight, although one brand in my local supermarket contains 7.4% sodium hypochlorite.

Sodium hypochlorite is a very unstable substance and reacts chemically with the water in the bleach container. A variety of reactions may occur, but the most common ones are described below.

Production of Hypochlorous Acid

The reaction between NaOCl and water produces produces HOCl, or hypochlorous acid, and sodium hydroxide, or caustic soda, as shown in the following chemical equation.

NaOCl + H2O → HOCl + NaOH

Hypochlorous acid is responsible for bleach's ability to remove colour from objects and for its ability to disinfect surfaces.

Production of the Hypochlorite Ion and Oxygen

The NaOCl also breaks down to produce the hypochlorite ion, or OCl-. This ion decomposes into a very reactive form of oxygen and a chloride ion. Like hypochlorous acid, the oxygen can remove colour from items, but to a lesser extent.

Removing Colour with Bleach - An Art Technique

How Does Bleach Whiten Fabrics?

Sodium hypochlorite is classified as an oxidizing agent. An oxidizing agent takes electrons from other chemicals when it reacts with them.

Using its oxidizing ability, NaOCl (or the HOCl that it produces) breaks chemical bonds inside chromophores, which are the parts of molecules which give them colour. This causes the chromophores to either change their bonding structure or to break up. The ability of the chromophores to absorb and reflect light is altered and they are unable to produce colour. In this way the NaOCl removes stains from fabrics and also lightens their overall colour.

Bleach can be very useful in the kitchen.
Bleach can be very useful in the kitchen. | Source

How Does Bleach Kill Germs?

Sodium hypochlorite reacts with proteins in microbes, denaturing them, or changing their shape. A protein is made of one or more chains of amino acids. Each chain is twisted and folded into a specific shape. If the shape changes, the protein can no longer do its job.

The hypochlorous acid that forms when sodium hypochlorite reacts with water causes microbe proteins to denature and then clump together, forming a non-functional mass. This kills the microbes.

Antibacterial Action of Bleach

The Importance of Diluting Bleach

Bleach that is bought in stores for cleaning and disinfecting needs to be diluted with water before use. The dilution factor depends on the starting concentration of the bleach. It's important to look at the container to see the manufacturer's recommendations. The company's website should also be a good resource for both dilution recipes for different uses and for cleaning suggestions. The CDC link at the end of this article should be helpful in this respect as well. The idea is to dilute the bleach so that it's safe and economical to use but not to dilute it so much that it's no longer effective.

Diluted bleach will only be effective for about a day (twenty-four hours) or sometimes for an even shorter time. Even undiluted bleach has a shelf life and will eventually become ineffective. Once the NaOCl in bleach has finished reacting, salt (NaCl) and water are left. The container's "use by" date should be noted. This date is not a guarantee of the bleach's safety, though. Since we can't see the chemicals in a container of bleach, we don't know when they've finished reacting.

When diluting and using bleach it's important to work in a well-ventilated area, since the vapour may irritate the eyes and airways. It's also a good idea to wear protective gloves. Dilute solutions of bleach may be mildly irritating, but concentrated solutions can burn.

There are lots of uses for bleach in a bathroom.
There are lots of uses for bleach in a bathroom. | Source

Uses of Bleach as a Disinfectant and Cleanser

Bleach is an excellent germ killer and can be very helpful in a home. For example, bleach can:

  • remove mold and mildew from bathroom tiles and shower curtains
  • clean shower mats
  • remove plants from cracks in a driveway or path
  • clean concrete
  • clean surfaces on which raw foods have been placed, such as cutting boards
  • clean kitchen counters
  • clean refrigerators and stoves
  • clean floors
  • clean porcelain toilets (but make sure that you read the "Bleach Dangers" section below before you do this!)
  • disinfect door handles, toilet flushers and faucets
  • disinfect sinks
  • disinfect garbage cans
  • disinfect non-porous toys
  • disinfect pet areas, such as litter trays and bird cages
  • disinfect garden tools to prevent spreading an infection from one plant to another
  • act as a cut flower preservative

Bleach is useful for cleaning bathroom tiles. As in any cleaning job with bleach, however, the correct concentration is important. Safety and effectiveness need to be combined.
Bleach is useful for cleaning bathroom tiles. As in any cleaning job with bleach, however, the correct concentration is important. Safety and effectiveness need to be combined. | Source

If cleaning instructions say to use a 1:10 bleach solution, they mean that one part of bleach should be mixed with nine parts of water. For example, mixing one cup of bleach with nine cups of water would create a 1:10 solution.

How to Kill Germs With Bleach

If bleach is being bought specifically to kill germs, it's important to read the bottle label carefully. The more concentrated solutions should have a word like "disinfectant" on the label. The less concentrated solutions are used as laundry bleaches and may not be able to kill germs.

Bleach that is being used to disinfect surfaces should be left in contact with the surface for at least five minutes (or ten minutes for some microbes) before being rinsed off. The surface should then be allowed to air dry whenever possible. It's important to think about the materials that are used to rinse or dry an item after it's been sanitized with bleach. If a contaminated cloth is used it will re-introduce germs to the area.

Sodium hypochlorite is used as a bleach in some swimming pools.
Sodium hypochlorite is used as a bleach in some swimming pools. | Source

Sodium Hypochlorite in Drinking Water and Swimming Pools

The safety of bleach is related to its concentration. Sodium hypochlorite is often used to disinfect drinking water and swimming pool water. When some people hear this, they think that they drink or swim in bleach. In fact, they do, since bleach is simply sodium hypochlorite dissolved in water! The concentration of NaOCl is kept to a safe level in water that's designed for human use, however.

A human and dog water fountain; many communities disinfect drinking water with sodium hypochlorite
A human and dog water fountain; many communities disinfect drinking water with sodium hypochlorite | Source

Laundry Bleach

Bleach can also be useful when doing the laundry. The bleach can be added to detergent to clean and brighten white fabrics or the fabrics can be soaked in bleach to remove a stain.

The washing instructions on a fabric and the instructions on the bottle of bleach should be followed carefully. The labels on some bleach containers say that the product is safe for certain types of colorfast fabrics, but it may be advisable to test the product on a small, hidden area of the fabric first.

Bleach may also weaken the material used to make an item of clothing if it's used over a long period of time. Some laundry bleaches contain an additive ("Fiber Guard") to protect fabrics and keep them strong.

How to Bleach White Clothes

Bleach Dangers

Sodium hypochlorite is very reactive, so it's important to take safety precautions, even with diluted bleach. Bleach must be kept in a firmly closed container which is labelled carefully and kept out of the reach of children and pets.

Here are some potential dangers of NaOCl.

  • When NaOCl reacts with light it produces dangerous chlorine gas (Cl2). Chorine is also made when the solution is heated. Even at room temperature, some chlorine escapes from the solution.
  • The caustic soda in bleach can irritate or burn skin, depending on its concentration.
  • Bleach is corrosive, especially at higher concentrations.
  • Bleach and cleansers containing ammonia must never be mixed. They react to produce a dangerous gas that contains toxic chloramine. The bleach must also be kept away from acids (including vinegar), rust remover and toilet bowl cleaner.

If safety precautions are followed, bleach is a great substance to have in a home. It improves the appearance of fabrics, cleans surfaces and can be an excellent germ killer. Even hospitals use it to kill dangerous microbes!

Disinfection According to the CDC (Centers for Disease Control and Prevention)

The CDC has a webpage that discusses disinfection in a hospital setting, but a lot of the information applies to homes, too. The "Chlorine and Chlorine Compounds" section describes the dilutions and exposure times needed to kill various microbes, using household bleach containing 5.25% to 6.15% sodium hypochlorite.

© 2013 Linda Crampton

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Comments 30 comments

billybuc profile image

billybuc 3 years ago from Olympia, WA

Having taught science for a number of years, I give you an A+ for your report. :) Good job Alicia. I hope you are enjoying this beautiful summer we are having.

bill


AliciaC profile image

AliciaC 3 years ago from British Columbia, Canada Author

Thank you very much for the A+, Bill. I appreciate it!! Yes, I'm enjoying the summer very much. There's been so much good weather this year. I hope you enjoy the rest of the weekend.


Sue Bailey profile image

Sue Bailey 3 years ago from South Yorkshire, UK

I love bleach; I use it all the time Alicia. I never even thought about the 'mechanics' of it so this was very interesting to me. Voted up and interesting and shared and pinned. Thank you


havingmysay profile image

havingmysay 3 years ago from USA

That was a very informative hub on bleach. I know there were many times when I was younger when I ruined clothes of mine with its splatter or had to run out the room because I used too much when cleaning. One question, I once heard (or read-I can't remember) that you can kill ringworm by taking a bleach-filled swab and placing it on the area of your skin. While this was not recommended, in your research is that possible?


AliciaC profile image

AliciaC 3 years ago from British Columbia, Canada Author

Thank you very much for the comment, the vote and the shares, Sue! I appreciate them all.


AliciaC profile image

AliciaC 3 years ago from British Columbia, Canada Author

Thanks for the visit and the comment, havingmysay. I've read claims that bleach has helped some people's ringworm, but I've never seen any scientific research about this idea. The thought of deliberately putting bleach on the skin is scary! The effects can range from an irritation to a serious burn.


havingmysay profile image

havingmysay 3 years ago from USA

Thanks for responding AliciaC! Yes, it is quite scary after reading all about such a powerful solution and then considering that people actually let it seep into their skin...on purpose! Thanks again for your research!


AliciaC profile image

AliciaC 3 years ago from British Columbia, Canada Author

Thank you very much, havingmysay.


bdegiulio profile image

bdegiulio 3 years ago from Massachusetts

Hi Linda. What a fascinating read on something that we use day in and day out. I never stopped to think exactly how does bleach work. Thank you for the great explanation that even I can understand. Great job. Voted up, shared, etc... Have a great week.


AliciaC profile image

AliciaC 3 years ago from British Columbia, Canada Author

Thank you very much for commenting and for the vote and the share, Bill. I hope you have a great week, too!


moonlake profile image

moonlake 3 years ago from America

I use bleach and cleaned my bathroom with it yesterday. Later when I took my sweat pants off I found a big white print on the back of my sweats. I must have wiped my hand on my pants. I just have to learn not to wear good clothes while handling bleach. Voted up on your hub.


AliciaC profile image

AliciaC 3 years ago from British Columbia, Canada Author

Thank you for sharing your experience - which a great warning for us all - and thanks for the vote, too, moonlake!


Eiddwen profile image

Eiddwen 3 years ago from Wales

Interesting and useful Alicia; thanks for sharing.

Eddy.


AliciaC profile image

AliciaC 3 years ago from British Columbia, Canada Author

Thanks for the visit and the comment, Eddy.


aviannovice profile image

aviannovice 3 years ago from Stillwater, OK

Bleach is one of the best things made available to us, but like you say, it must be used properly. A great article for such a simple cleaner/disinfectant.


AliciaC profile image

AliciaC 3 years ago from British Columbia, Canada Author

Thank you, Deb. I appreciate your comment.


Laura in Denver profile image

Laura in Denver 3 years ago from Aurora

Interesting hub and appropriate videos. I have tended to avoid bleach because to me it stinks, but I also, I had a mishap with bleach cleaner plus ammonia cleaner reacting! For this reason, it is wise to CAREFULLY read all the ingredients in your cleaners. Thanks!


AliciaC profile image

AliciaC 3 years ago from British Columbia, Canada Author

Thanks for the comment and for emphasizing the potential dangers of bleach, Laura!


teaches12345 profile image

teaches12345 3 years ago

As a former child care director, we used bleach regularly to disinfect just about every inch of the place. It is especially useful during cold season. Great post, as always!


drbj profile image

drbj 3 years ago from south Florida

Alicia - My housekeeper once told me, "... if you ain't cleanin' with bleach, you ain't cleanin'." She must have read your hub. :)


AliciaC profile image

AliciaC 3 years ago from British Columbia, Canada Author

Hi, Dianna. Bleach can be amazingly useful! People often think of it as a simple substance, but it's really very helpful. Thanks for the comment and for sharing the information.


AliciaC profile image

AliciaC 3 years ago from British Columbia, Canada Author

Your housekeeper sounds like a wise person, drbj! Thanks for the visit and the comment.


Pamela99 profile image

Pamela99 3 years ago from United States

I have always used bleach to do a lot of cleaning and with laundry. You still listed several facts that I didn't know. Very useful hub.


AliciaC profile image

AliciaC 3 years ago from British Columbia, Canada Author

Thank you very much for the comment, Pamela.


DDE profile image

DDE 3 years ago from Dubrovnik, Croatia

How Bleach Works - Disinfection and Stain Removal a well advised article on this topic and you have informed us to the point and shared the simple ways of how bleach works and what it is used for in other circumstances .


AliciaC profile image

AliciaC 3 years ago from British Columbia, Canada Author

Thanks for the visit and the comment, DDE.


CraftytotheCore profile image

CraftytotheCore 3 years ago

Such interesting facts about bleach! I had no idea it can act as a cut flower preservative or be used in art. Amazing!


AliciaC profile image

AliciaC 3 years ago from British Columbia, Canada Author

Thank you very much, Crafty! I appreciate your comment.


Greensleeves Hubs profile image

Greensleeves Hubs 2 years ago from Essex, UK

Comprehensive article on all things connected with bleach, including of course the science, Linda. It occurs to me that the application of science to such seemingly mundane household products as bleach is a great way of teaching how science - in this case molecules and chemical reactions - has practical applications for us all.

And for some who have never had an interest in chemistry because they don't see how it directly affects them, it may bring the subject to life.


AliciaC profile image

AliciaC 2 years ago from British Columbia, Canada Author

Hi, Alun. I agree. Learning about the chemistry of substances and materials that we encounter every day could bring science to life! Thank you very much for the comment.

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