Chlorine-releasing compounds
Clinical data | |
---|---|
Other names | Chlorine-releasing disinfectants,[1] chlorine base compounds, chlorine-releasing bleach, chlorine based bleach |
Drug class | Disinfectant |
ATC code |
Chlorine-releasing compounds, also known as chlorine base compounds, is jargon to describe certain chlorine-containing substances that are used as disinfectants and bleaches. They include the following chemicals:
Side effects if contact occurs may include skin irritation and
Chlorine-releasing compounds first came into use as bleaching agents around 1785,[5] and as disinfectants in 1915.[6] They are on the World Health Organization's List of Essential Medicines.[7] They are used extensively in both the medical and the food industry.[4]
Uses
Chlorine-based compounds are usually handled in water solutions, powders, or tablets, that are mixed with water before use.[2] They may have to be rinsed off after application to avoid corrosion of metals and degradation of organic materials.[3]
Disinfectants
Chlorine-based compounds are effective against a wide variety of
The presence of other organic matter in the place of application can make these disinfectants less effective, by consuming some of the released chlorine.[3]
Whitening agents
Chlorine-based bleaches have been used since the late 18th century to whiten
Colors of natural materials typically arise from organic
Industrially, chlorine-based bleaches are used in a wide variety of processes, including bleaching of wood pulp.
Safety
Chlorine-releasing products present significant risks. It is estimated that, in 2002, there were about 3300 accidents needing hospital treatment caused by liquid bleach in British homes, and about 160 due to bleaching powder.[8]
Chemical burns
Chlorine releasing solutions, such as liquid bleach and solutions of bleaching powder, can burn the skin and cause eye damage,[2] especially when used in concentrated forms. As recognized by the NFPA, however, only solutions containing more than 40% sodium hypochlorite by weight are considered hazardous oxidizers. Solutions less than 40% are classified as a moderate oxidizing hazard (NFPA 430, 2000).
Release of chlorine gas
Mixing a hypochlorite bleach with an acid can liberate chlorine gas.
Chlorine is a respiratory
Reaction with other products
Chlorine releasing compounds can react with other common household chemicals like vinegar or ammonia to produce toxic gases.
Mixing an
- Cl2 + H2O ⇌ 2H+ + Cl− + ClO−
A hypochlorite bleach can react violently with hydrogen peroxide and produce oxygen gas:
- H2O2(aq) + NaOCl (aq) → NaCl (aq) + H2O(l) + O2(g)
A 2008 study indicated that sodium hypochlorite and organic chemicals (e.g., surfactants, fragrances) contained in several household cleaning products can react to generate chlorinated
The hypochlorites in liquid bleach and bleaching powder can react with ammonia to form a number of products, including
Corrosion
Chlorine releasing products may also cause corrosion of many materials and unintended bleaching of colored products.[3]
Neutralization
Sodium thiosulfate is an effective chlorine neutralizer. Rinsing with a 5 mg/L solution, followed by washing with soap and water, will remove chlorine odor from the hands.[16]
Main compounds
Specific compounds in this family include:[2][4]
- Eau de Labarraque or "Labarraque's water",[17] is widely marketed as a household cleaning product, under the name "liquid bleach" or simply "bleach". More concentrated solutions are used to disinfect drinking water and as bleaching agents in industrial processes. A more diluted solution (up to 0.5%) has been in use since 1915 to cleanse and disinfect wounds, under the name of Dakin's solution.[17][18][19][2]
- Calcium hypochlorite, Ca(OCl)
2.[20] This product, known as "bleaching powder" or "chlorinated lime", it is used in many of the same applications as sodium hypochlorite, but is more stable and contains more available chlorine. It is usually marketed as a white powder that contains, besides the hypochlorite, also calcium hydroxide Ca(OH)
2 ("lime") and calcium chloride CaCl
2.[21] A purer, more stable form of calcium hypochlorite is called HTH or high test hypochlorite. It is also available as bleaching tablets that contain calcium hypochlorite and other ingredients to prevent the tablets from crumbling. A supposedly more stable mixture of calcium hypochlorite and quicklime (calcium oxide) is known as "tropical bleach".[22] Percent active chlorine in these materials ranges from 20% for bleaching powder to 70% for HTH. - Potassium hypochlorite, KOCl. This was the first chlorine-based bleaching agent, which became available around 1785 under the name Eau de Javel or "Javel water". It is no longer commonly used, having been superseded by the cheaper sodium analog.
- Chloramine, NH
2Cl. This chemical is commonly handled as a dilute aqueous solution. It is used as an alternative to chlorine and sodium hypochlorite for disinfection of drinking water and swimming pools. - Chloramine-T, or tosylchloramide sodium salt, [(H
3C)(C
6H
4)(SO
2)(NHCl)]−
Na+
. This solid compound is available in tablet or powder form, and used in medical establishments to disinfect surfaces, equipment, and instruments.[2] - Sodium dichloroisocyanurate [((ClN)(CO))
2(NCO)]−
Na+
. This solid compound, available as tablets, is widely used as a disinfectant, to sterilize drinking water, swimming pools, tableware, farming installations, and air; and as an industrial deodorant. It is also used for bleaching textiles.[2] - Halazone, or 4-((dichloroamino)sulfonyl)benzoic acid, (HOOC)(C
6H
4)(SO
2)(NCl
2). This compound was for a while used to disinfect drinking water in field situations, but has largely been replaced in that use by sodium dichloroisocyanurate.[2] - Chlorine dioxide, ClO
2.[23] This is an unstable gas, which is usually prepared in situ or stored as dilute aqueous solutions. Despite these limitations it finds large-scale applications for the bleaching of wood pulp, fats and oils, cellulose, flour, textiles, beeswax, skin, and in a number of other industries. It has also been used for chlorination of tap water.
Mechanism of action
The activity and applications of chlorine-releasing compounds are diverse. Some have strong oxidizing character. Chlorine readily inserts itself into double bonds, including those of aromatic rings, creating chlorinated organic compounds. This accounts for its bleaching action, since many colored organic substances owe their color to compounds with such bonds.[citation needed]
The extensive reactivity of chlorine is also responsible for its broad antimicrobial effect, since it can destroy or denature many proteins and other chemicals that are essential for microbes' metabolism.
Free chlorine
The strength of chlorine-releasing solutions, as well as their dosage in uses like water chlorination and pool sanitization, is usually expressed as
The strength of commercial chlorine-releasing products may be instead specified as the concentration of the active ingredient, as
A typical oxidation reaction is the conversion of iodide I−
to elemental iodine I
2. The relevant reactions are
- NaClO + 2 H+
+ 2 I−
→ NaCl + H
2O + I
2 - Cl
2 + 2 H+
+ 2 I−
→ 2 Cl−
+ H
2O + I
2
That is, one "molecule" of NaClO has the same oxidizing power as one molecule of Cl
2. Their molar masses are 74.44 g and 70.90 g, respectively. Therefore, 1 kilogram of the solution has 1000 × 0.05 × 70.90/74.44 = 47.62 g of "free chlorine".
In order to convert between mass ratios and mass per volume, one must take into account the density of the liquid in question. For chlorinated water, one can assume the density is the same as of pure water, about 1000 g/L (more precisely, about 997 g/L at 25 °C). For more concentrated solutions like liquid bleach, the density depends on the ingredients and their concentrations, and is usually obtained from tables.[24] When diluting a product, one must be aware that the volume of the diluted solution may not be the sum of the volumes of product and water. For example, one ml of 5.25 wt% NaClO bleach added to ten liters of water, will yield a NaClO concentration of about 5.76 mg/L, and 5.48 mg/L of free chlorine.[24]
History
Scottish chemist and industrialist Charles Tennant proposed in 1798 a solution of calcium hypochlorite as an alternative for Javel water, and patented bleaching powder (a solid product containing calcium hypochlorite) in 1799.[26]
Around 1820, French chemist Labarraque discovered the disinfecting ability of hypochlorites, and popularized the use of the cheaper sodium hypochlorite solution (known as Eau de Labarraque, "Labarraque's water") throughout the world for that purpose.[27] His work greatly improved medical practice, public health, the sanitary conditions in hospitals, slaughterhouses, and all industries dealing with animal products—decades before Pasteur and others established the germ theory of disease.[28] In particular, it led to the nearly universal practice of chlorination of tap water to prevent the spread of diseases like typhoid fever and cholera.[29][6]
In 1915, British chemist Henry Dakin, working at a field hospital in France during World War I, did an extensive study of compounds that could be used to disinfect wounds and prevent sepsis. He found that chloramine was optimal, but settled for a dilute sodium hypochlorite solution—still used today with the name of "Dakin's solution"—for reasons of cost and availability.[19][17]
See also
References
- ISBN 9781139445290.
- ^ ISBN 9789241547659.
- ^ ISBN 9781461535461.
- ^ ISBN 9780683307405.
- ISBN 9780857093691.
- ^ ISBN 9780080548487.
- hdl:10665/325771. WHO/MVP/EMP/IAU/2019.06. License: CC BY-NC-SA 3.0 IGO.
- ^ Royal Society for the Prevention of Accidents (2002): 24th Report of the Home and Leisure Accident Surveillance System (HASS)., page 150. Accessed on 2018-06-18.
- ^ OSHA (2018): "Table Z-1". Appendix to Permissible Exposure Limits – Annotated Tables. Published by U. S. Occupational Safety and Health Administration. Accessed on 2018-06-18.
- ISBN 978-0615702179.
- ISBN 0-471-17560-9.
- ^ PMID 18441786.
- ^ Rizk-Ouaini R, Ferriol M, Gazet J, Saugier-Cohen A, Therese M (1986). "Oxidation reaction of ammonia with sodium hypochlorite. Production and degradation reactions of chloramines". Bulletin de la Société Chimique de France. 4: 512–521.
- ISBN 9780683080278.
- S2CID 24606118.
- ISBN 978-0-87553-047-5. Method 9060a. Also available on CD-ROM and onlineby subscription.
- ^ a b c Daufresne M (1916). Mode de préparation de l'hypochlorite de soude chirurgical - Differénce entre la soulution de Dakin et celle de Labarraqu. Vol. xxiv. Presse médicale. p. 474.
- PMID 20767784.
- ^ a b Dakin HD, Kunham EK (1918). A Handbook of Antiseptics. New York: Macmillan.
- ISBN 9780323142304.
- S2CID 96905077.
- ^ "Calcium Hypochlorite: Different forms of calcium hypochlorite" (PDF). World Health Organization. Retrieved 27 May 2012.
- ISBN 9781118251164.
- ^ a b c "OxyChem Sodium Hypochlorite Handbook" (PDF). oxy.com. OxyChem. Archived from the original (PDF) on 2018-04-18. Retrieved 2018-06-13.
- ^ "Pamphlet 96, The Sodium Hypochorite Manual". www.chlorineinstitute.org. The Chlorine Institute.
- ^ a b c Chisholm H, ed. (1911). . Encyclopædia Britannica (11th ed.). Cambridge University Press.
- ^ Labarraque AM (1828). On the disinfecting properties of Labarraque's preparations of chlorine. Translated by Scott J. S. Highley.
- ^ "Labarraque AG". Nouvelle Biographie Générale. 28: 323–324. 1859.
- ^ Reece RJ (1907). Report on the Epidemic of Enteric Fever in the City of Lincoln, 1904-5. Thirty-Fifth Annual Report of the Local Government Board, 1905-6: Supplement Containing the Report of the Medical Officer for 1905-6. (Report). London: Local Government Board.