Re: Question-Answer about disinfectants
Runninghorses, I plan to do so. First mix up the granulated calcium hypochlorite with the right amount of water for a common household bleach solution, then add water as per directions to further reduce the hypochlorite content and then add the small amount of vinegar to acidify the bleach solution.
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Calcium hypochlorite:
http://en.wikipedia.org/wiki/Calcium_hypochlorite
Calcium hypochlorite
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Calcium hypochlorite Image:Calcium hypochlorite.jpg Systematic name Calcium hypochlorite Other names HTH
Molecular formula Ca(ClO)2
Molar mass 143.1 g/mol
Density x.xxx g/cm3
Solubility (
water) x.xx g/l
Melting point xx.x ?C
Boiling point xx.x ?C
CAS number [xx-xx-xx]
Disclaimer and references Calcium hypochlorite is a
chemical compound with
formula Ca(
ClO)2. It is widely used for
water treatment and as a
bleaching agent (bleaching powder). This chemical is considered to be relatively stable and has greater available
chlorine than
sodium hypochlorite (liquid bleach).
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Preparation
It is manufactured using the calcium process and sodium process. Or it can be prepared by the action of slaked lime on
chlorine:
Ca(OH)2 + Cl2 → Ca(OCl)2 + H2 [
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Properties
It is a yellow white solid which has a strong smell of
chlorine. Calcium hypochlorite is not highly soluble in water. For that reason it should preferably be used in soft to middle hard water. There are two types of calcium hypochlorite - a dry form and a hydrated form. The hydrated form is safer to handle.
Calcium hypochlorite reacts with
carbon dioxide to form
calcium carbonate and release
chlorine:
Ca(OCl)2 + CO2 → CaCO3 + Cl2 Calcium hypochlorite reacts with
hydrochloric acid to form
calcium chloride:
Ca(OCl)2 + 2 HCl → CaCl2 + H2O + Cl2 [
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Uses
Calcium hypochlorite is used for the disinfection of drinking water or swimming pool water. For use in outdoor swimming pools, calcium hypochlorite can be used as a sanitiser in combination with a
cyanuric acid stabiliser. The stabiliser will reduce the loss of chlorine because of UV radiation.
Calcium hypochlorite is also used for bleaching cotton and linen and used in the manufacture of
chloroform.
Retrieved from "
http://en.wikipedia.org/wiki/Calcium_hypochlorite"
Categories:
Antiseptics |
Bleaches |
Hypochlorites |
Calcium compounds
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Sodium hypochlorite
http://en.wikipedia.org/wiki/Sodium_hypochlorite
Sodium hypochlorite
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Sodium hypochlorite
General Other names Sodium chlorate(I)
Molecular formula NaOCl
Molar mass 74.44 g/mol Appearance white solid
CAS number [7681-52-9] Properties
Density and
phase ?
Solubility in
water Fully miscible
Melting point 18 ?C Pentahydrate
Boiling point ? ?C Decomposes
Acidity (p
Ka) ?
Basicity (p
Kb) ? Hazards
EU classification Corrosive (
C)
Dangerous for
the environment (
N)
R-phrases R31, R34, R50
S-phrases S1/2, S28, S45,
S50, S61
NFPA 704
Related compounds Other
anions Sodium chloride
Sodium chlorite
Sodium chlorate
Sodium perchlorate Other
cations Lithium hypochlorite
Calcium hypochlorite Related compounds
Hypochlorous acid Except where noted otherwise, data are given for
materials in their
standard state (at 25 ?C, 100 kPa)
Infobox disclaimer and references Sodium hypochlorite is a
chemical compound with the
formula NaOCl. A solution of sodium hypochlorite is frequently used as a
disinfectant and as a
bleaching agent; indeed, often it is simply called "bleach", though other chemicals are sometimes given that name as well.
Contents
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Production
Sodium hypochlorite may be prepared by absorbing
chlorine gas in cold
sodium hydroxide solution:
2NaOH + Cl2 ⇌ NaCl + NaOCl + H2O Sodium hydroxide and chlorine are commercially produced by the
chloralkali process, and there is no need to isolate them to prepare sodium hypochlorite. Hence NaOCl is prepared industrially by the
electrolysis of
sodium chloride solution without any separation between the
anode and the
cathode. The solution must be kept below 40 ?C (by cooling coils) to prevent the formation of
sodium chlorate.
The commercial solutions always contain significant amounts of sodium chloride (common salt) as the main byproduct, as seen in the equation above.
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Packaging and sale
Household bleach sold for use in laundering clothes is a 3-6
% solution of sodium hypochlorite at the time of manufacture. Strength varies from one formulation to another and gradually decreases with long storage.
A 12% solution is widely used in waterworks for the chlorination of water. High-test hypochlorite (HTH) is sold for chlorination of swimming pools and contains approximately 30% sodium hypochlorite. The crystalline salt is also sold for the same use; this salt usually contains less than 50% of sodium hypochlorite. However, the level of "active chlorine" may be much higher.
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Uses
In household bleach form, sodium hypochlorite is used for removal of stains from laundry. It is particularly effective on cotton fiber, which stains easily but bleaches well. 50 to 250 ml per load is usually recommended for a standard-size washer. Hot water increases the activity of the bleach, owing to the thermal decomposition of hypochlorite which ultimately generates environmentally-undesirable chlorate.
A weak solution of 1 % household bleach in warm water is used to sanitize smooth surfaces prior to brewing of beer or wine. Surfaces must be rinsed to avoid imparting flavors to the brew; these chlorinated byproducts of sanitizing surfaces are also harmful.
A 1 in 5 dilution of household bleach with water (1 part bleach to 4 parts water) is effective against many
bacteria and some
viruses, and is often the disinfectant of choice in cleaning surfaces in hospitals (Primarily in the United States). The solution is
corrosive, and needs to be thoroughly removed afterwards, so the bleach disinfection is sometimes followed by an
ethanol disinfection.
For
shock chlorination of wells or water systems, a 2% solution of household bleach is used. For larger systems, HTH is more practical because lower rates can be used. The alkalinity of the sodium hypochlorite solution also causes the precipitation of minerals such as calcium carbonate, so that the shock chlorination is often accompanied by a clogging effect. The precipitate also preserves bacteria, making this practice somewhat less effective.
Sodium hypochlorite has been used for the disinfection of drinking water, at a concentration equivalent to about 1 liter of household bleach per 4000 liters of water is used. The exact amount required depends on the water chemistry, temperature, contact time, and presence or absence of sediment. In large-scale applications, residual chlorine is measured to titrate the proper dosing rate. For
emergency disinfection, the US
EPA recommends the use of 2 drops of 5%ac household bleach per quart of water. If the treated water doesn't smell of bleach, 2 more drops are to be added.
The use of chlorine-based disinfectants in domestic water, although widespread, has led to some controversy due to the formation of small quantities of harmful byproducts such as
chloroform.
It is also used in
dentistry, during root canal treatment, disinfecting the canal and dissolving any remaining pulp tissue. Historically,
Henry Drysdale Dakin's solution (0.5%) had been used. Nowadays, 2.5-5.25% solutions are being used.
An alkaline solution (pH 11.0) of sodium hypochlorite is used to treat dilute (< 1 g/L) cyanide wastewater, e.g. rinsewater from an electroplating shop. A well-mixed solution is fully treated when an excess of chlorine is detected. More concentrated cyanide solutions are much more difficult to dispose of.
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Mechanism of action
Like all hypochlorites, sodium hypochlorite is a
salt of
hypochlorous acid, HClO. Sodium hypochlorite is a colorless, transparent liquid. In water, it partially splits into the sodium
cation Na+ and the
hypochlorite anion ClO-, while a substantial portion
hydrolyses into
sodium hydroxide and
hypochlorous acid. The
oxidizing power of the latter and of the hypochlorite anion cause the bleaching effect. Its negative charge, however, prevents it from diffusing through the cell walls of bacteria and microbes, making it a poor disinfectant. However the hypochlorous acid molecules that exist in equilibrium with the hypochlorite anion, due to their neutral charge and small size, easily diffuse through the cell walls of bacteria. This changes the oxidation-reduction potential (ORP) of the cell, and inactivates the enzyme
triosephosphate dehydrogenase. Triosephosphate dehydrogenase (or
glyceraldehyde 3-phosphate dehydrogenase/GAPDH) is essential for the digestion of glucose, but is particularly sensitive to oxidizing agents. Its inactivation effectively destroys the micro-organism's ability to function.
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Cautions
Hypochlorite is a strong oxidizer, and the products of the oxidation reactions are corrosive, and can burn skin and cause eye damage, particularly when used in concentrated forms. Hypochlorite must not be mixed with organic materials (e.g. dirt), as the resulting
trihalomethanes (also called haloforms) are carcinogenic. The extent of the hazard thus created is a subject of disagreement.
Bleach should never be mixed with other household cleaners, especially not with ones containing
acid, since this results in the generation of
chlorine gas. It should also never be mixed with anything containing
ammonia, since
chloramine gas can be gained from this combination.
Urine contains ammonia, so bleach should not be used to clean urine spills. Both chlorine gas and chloramine gas are highly
toxic. Bleaches also react rather violently with
hydrogen peroxide.
It is estimated that there are about 3300 accidents needing hospital treatment caused by sodium hypochlorite solutions each year in British homes (RoSPA, 2002).
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See also
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Bibliography
- Jones, F.-L. (1972). "Chlorine poisoning from mixing household cleaners". J. Am. Med. Assoc. 222: 1312.
- Institut National de Recherche et de S?curit?. (2004). "Eaux et extraits de Javel. Hypochlorite de sodium en solution". Fiche toxicologique n? 157, Paris.
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External links
Retrieved from "
http://en.wikipedia.org/wiki/Sodium_hypochlorite"
Categories:
Sodium compounds |
Hypochlorites |
Antiseptics |
Disinfectants |
Bleaches
