Commonly the most dangerous chemical found in a household, bleach is an inorganic aqueous
solution of 5.25% sodium hypochlorite
. Bleach is a clear to yellowish liquid with a distinct chlorine
like odor. Often mistakenly referred to as "chlorine bleach" because of its strong smell, bleach does not release a considerable amount of chlorine gas during its normal mode of action. Bleaches often include sodium hydroxide
to maintain a pH-dependent equilibrium between the hypochlorite
the solution contains. Household bleach normally has a very alkali pH
of around 12.5, and it is highly corrosive
. Different solution strengths are marketed for different uses. High strength bleach is usually a 10% sodium hypochlorite solution
, and some industrial bleaches may be up to 50%. Pool
chlorine is usually 12%.
Household bleach is an unstable solution
. Chlorine evaporates from it at a rate of 0.75 gram active per day. When heated to temperature above 40C, or placed in direct sunlight, bleach disintegrates into its component chemicals. It is vigorous
ly reactive with many chemicals, is a strong oxidator
and reacts with flammable compounds and reductors.
Given these facts, why would any one want to have bleach around?
The key is disinfection
. Every day, millions of households throughout the world
rely on sodium hypochlorite bleach for their disinfection, deodorizing and cleaning
needs. Bleach has long been recognized as having outstanding disinfective properties. The Institute Pasteur
lists it as the most effective disinfectant
against all known pathogenic bacteria
es. Its low cost
and ready availability makes it an invaluable weapon for the maintenance of human
health and proper preventative hygiene
, throughout the world. It is also used in the removal of mold
relied on bleach during the Apollo
program to assure destruction of any potentially harmful organisms introduced from space by returning spacecraft
. It has the advantage that microorganism
s cannot build up any resistance
to it. It can be produced, stored and transported, and used easily and safely. Dosage
calculation is simple. Sodium hypochlorite bleach is as chemically effective
as chlorine gas for disinfection and it leaves residual disinfectant products when used. In Canada, "Javex
" brand bleach has been sold continuously since 1935. It definitely has a commercial future.
How does bleach disinfection work?
By adding hypochlorite to water, hypochlorous acid (HOCl) is formed:
NaOCl + H2O = HOCl + NaOH-
Hypochlorous acid is divided into hydrochloric acid (HCl) and oxygen (O). The oxygen atom is a very strong oxidator.
What else is it good for?
Bleach is also used as a whitener
, stain remover
. When used as a supplement to laundry detergent
, It is highly effective at removing a wide range of tough stains e.g. blood
, body soil
, and red wine
. Conversely, one of the hazards of laundry bleach use is the tendency for it to blanch
bright colors and weaken
fibers. If directly dripped on fabrics, it can cause spotting or even hole
s. Bleach is more commonly used when washing white clothing as a brightening agent
Not happy with the title of "World's Most popular Germ-Killer", bleach is also used in great quantities by industries worldwide. An enormous commercial market
for industrial bleach
exists, where it used for waste water treatment
, drinking water
disinfection and textile
manufacturing. It is used to treat sewage
and industrial wastes to reduce odors and increase digesting efficiency. Hypochlorite bleach neutralizes sulphur hydrogen
gas (SH) and ammonia
(NH3). It detoxifies cyanide
baths in metal finishing industries and treats cyanide effluent
s created by gold
mining. Bleach is also used to recover precious metals from manufacturing solutions. Air scrubbing
systems use bleach to destroy pathogen
s and neutralize gases. Without bleach, much of the food processing
done in North America
would not be possible. It is used to clean dairy equipment and food processing equipment, in fruit, vegetable, mushroom, hog, beef, poultry, fish and maple syrup
processing. One of the first uses for commercial uses bleach was its use as a cotton
whitener. It remains one of the most important chemicals used in textile manufacturing
. Bleach is also used to whiten paper
and many other organic
The common smell of swimming pool
s is created by bleach. It is used in swimming pool water disinfection, both as a daily regimen and as a shock treatment. An interesting tidbit is that if a pool smells of chlorine
, it probably isn't very clean. When bleach reacts with ureum
(a mixture of urine and sweat), hypochlorous acid and ureum react to form chloramine
s. These chloramines irritate mucous membranes and cause the so-called 'chlorine smell'.
Who came up with this wonderful stuff?
French chemist Claude Louis Berthollet
, while working in the town of Javel
on the outskirts of Paris
, discovered sodium hypochlorite in 1787. Berthollet focused much of his work on the use of dye
s, and was primarily interested in bleaches when used to whiten textiles. His discovery was quickly put to commercial use
. The Javel Company
introduced bleach to France, naming the product 'eau de Javel'. It was so popular that bleach is still known by that colorful name in France
today. Another enterprising French scientist, Louis Pasteur
, discovered the potent effectiveness of bleach when used against disease-causing bacteria. After Pasteur detailed the unsurpassed disinfection spectrum
of bleach, its use as a disinfectant skyrocketed.
How is bleach made?
Sodium hypochlorite bleach is usually created in one of these two ways:
was is by creating a concentrated brine solution by dissolving salt
) in softened water (H20). By running electricity through this solution, sodium hypochlorite forms in water. This solution contains 150 g active chlorine (Cl2) per liter. During the electrolyzing reaction, explosive hydrogen gas
is also formed. This is the safest way? Actually, yes.
The far more dangerous
way to make bleach, which was also the method used by Berthollet, is by adding chlorine gas
(Cl2) to caustic soda (NaOH). When this is done, sodium hypochlorite, water (H2O) and salt
(NaCl) are produced according to the following reaction:
Cl2 + 2NaOH + = NaOCl + NaCl + H2O
This solution is also known as "Eau de Labarraque", and "Eau de Javel".
What are the danger of misusing bleach?
Bleach is made up of sodium
, some of the most reactive
of all chemicals. When bleach reacts with another substance, or is broken down in any way, these chemicals are released in ways that are rarely beneficial to biology
The most important thing to remember about bleach
around the house are other cleaning substances that it reacts with dangerously. Ammonium
, found in some cleaning products, mixed with sodium hypochlorite
evolves nitrogen trichloride
. Nitrogen trichloride smells like chlorine and is nearly as deadly. Deadly chlorine gas
is created when bleach and hydrochloric acid
are mixed, but few people use acid around the house for cleaning. As a strong base
, bleach should not be mixed with a strong acid
. That sort of thing is basic chemistry, what with the hydrogen ions
being passed around in an energetic manner.
Bleach decomposes slowly when stored properly, but decomposition
is speeded up by temperatures above 40 degrees C and light. While decomposing, bleach becomes chlorine gas, oxygen gas, and sodium chlorate
There are lots of other things you shouldn't mix bleach with. Nitrogen compounds
(e.g., ammonia, urea, amines, isocyanurates) can form toxic, reactive chloramines
and nitrogen gas. Methanol
and bleach can form methyl hypochlorite
, which is explosive. Metals, like copper
, speed up the decomposition of NaOCl, while others will rapidly corrode
because of oxygen reactions. Assume the worst
when using bleach, because it will react with almost anything.
So, you messed up. How can bleach kill you?
The previously mentioned nitrogen trichloride
gases cause burning in the throat and coughing. High levels of exposure
can lead to swelling and obstruction of the airway. In serious cases noncardiogenic pulmonary edema
can occur. Bleach will react with skin
and eyes causing corrosive
burns and tissue necrosis
. In small amounts it is a skin irritant
, and inhaled aerosols can inflame the lungs. It is very harmful
when ingested, as it reacts with the acidic
environment of the digestive tract. Extensive damage to the mouth, throat, eyes, lungs, esophagus, nose, and stomach are possible. Damage can continues to occur to the esophagus and stomach for several weeks after the alkali
was swallowed, and death may occur as long as a month later. If bleach is swallowed, vomiting
be induced. Give milk or water and seek emergency medical care immediately. If bleach is on the skin
, wash with lots of water. Ingested bleach can cause a severe change in blood pH
which can damage all internal organs
, but it is rare. Deaths caused by the misuse of bleach are extremely rare
is a known mutagenic
, but bleach is not a mutagen
or skin sensitizer
. The IARC (the International Agency for Research on Cancer) has concluded that chlorinated drinking water
is not a "classifiable" human carcinogen
. Bleach decomposition creates tiny amounts of absorbable organic halides
(AOX), which have potential negative health effects in humans. That being said, the majority of these AOXs are easily degradable
, are primarily water soluble
and not bio-accumulative
. Highly chlorinated species, such as dioxins
, are not formed.