Sodium hypochlorite is a chemical compound with chemical formula NaOCl. Sodium hypochlorite solution is commonly known as whitening agent or Clorox. This chemical compound is also used commonly as disinfectant as well. Sodium hypochlorite is first produced in 1789 by Claude Louis Berthollet in his laboratory in Paris, France. This chemical compound is made by passing the chlorine gas through sodium carbonate solution. The liquid that became the result of this reaction is known as weak sodium hypochlorite solution. However, this process is not efficient and the alternative production method is searched.
One of these methods involves calcium hypochlorite extraction using sodium carbonate in order to produce low levels chlorine. This method is commonly used to produce hypochlorite solution for antiseptic in hospital that is sold with trade name “Eusol.” Toward the end of 19th century, E.S. Smith patented the production method of sodium hypochlorite that involves salt water electrolysis in order to produce sodium hydroxide and chlorine gas that later combined to form sodium hypochlorite.
This process is known as chloralkali process. Both electrical power and salt water solution are available with affordable price that time. There are many marketers that take advantage of this situation to meet the market demand for sodium hypochlorite. Sodium hypochlorite solution that is bottled then sold with various brand names.
These days, one of the methods that are considered as improvement of chloralkali method is hooker process. This process is the only process that is used to produce sodium hypochlorite in large scale. In this process, sodium hypochlorite and sodium chloride are formed when chlorine is passed in low temperature state and dilute the sodium hydroxide solution.
This chemical compound is produced in industrial process through electrolysis with the minimal separation of anode and cathode. The solution should be kept under 40°C temperature (using circular freezer) to prevent the formation of sodium chlorate that is not expected. Since chlorine is reducted and oxidized gradually, then this process is known as disproportionation. This commercial solution always contains the significant amount of sodium chloride as main side product.
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The Uses of Sodium Hypochlorite
There are several applications of sodium hypochlorite uses in everyday life. Below are the applications of this chemical solution.
1. Whitening Agent
Whitening agent or also known as bleach for household is commonly the solution that contains 4-6% of sodium hypochlorite and 0.01-0.05% of sodium hydroxide while sodium hydroxide is used to delay the breakage of sodium hypochlorite into sodium chloride and sodium chlorate. For household purpose, sodium hypochlorite is used for getting rid of the stain from clothing.
This solution is very effective for stains on cotton fiber since it can remove the stains perfectly. For standard size washing machine, you only need to use 50 to 250ml of this solution depend on the amount of clothes that you want to wash. The properties of bleach for household that is effective for removing stains might also cause cumulative damage on organic fiber such as cotton. If you use the bleach regularly on clothes that are made of cotton, the durability of the clothes will be reduced. Sodium hydroxide that is also used in bleach might also cause fiber degradation as well.
This chemical compound can’t vaporize easily and the residue of sodium hydroxide that is not rinsed will keep damage the organic fiber slowly with helps from humidity. For this reason, if the stain only appears on certain spot, the treatment should be considered if necessary.
With caution, the treatment using vinegar (or weak acid) will neutralize the sodium hydroxide and vaporize the chlorine that came as residue from hypochlorite. T-shirt and cotton sheets that rip easily show the effect of using bleach when washing the clothes. Hot water can increase the effectiveness of bleach since there is the increase of reactivity of those molecules.
Weak solution from 2% household bleach that is added to warm water can be used for cleaning soft surface before the making of wine or beer. The surface needs to be rinsed to prevent the damage on the taste of those drinks. The side product that contains chlorine from the process of surface cleaning might also dangerous as well.
US government regulation (21 CFR part 178) allows direct contact with surface of food processing tools that are cleaned using solution that contains bleach as long as the solution can be rinsed as thoroughly as possible before it has direct contact with the foods and also the solution shouldn’t be contained chlorine more than 200 ppm (for example, one tablespoon of household bleach contains 5.25% of sodium hypochlorite per gallon of water).
If higher concentration is used, the surface should be rinsed with drinking water after sanitation. The dilution of household bleach using water (one part of bleach with 4 parts of water) is effective for many bacteria and some viruses. This solution is corrosive and really needs to be rinsed after being used.
Disinfection with bleach sometimes is followed with disinfection using ethanol. Disinfectant solution that is produced commercially such as Virocidin-X is usually contains sodium hypochlorite as single active ingredient even though this product also contains surfactant (to prevent spots) and fragrance (to conceal the smell of bleach).
3. Water treatment
For breakpoint chlorination of water or well system, solution of 3% household bleach can be used. For larger system, sodium hypochlorite is more practical since lower level of this chemical compound can be used. Alkalinity of sodium hypochlorite solution might also cause the sedimentation of minerals such as calcium carbonate so that breakpoint chlorination is commonly followed by clogging effect.
The sedimentation also might maintain bacteria as well so that this process is not too effective. Sodium hypochlorite has been used for drinking water disinfection. A concentration that is equivalent with about 1 liter of household bleach per 4000 liters of water is used for this purpose. The exact amount is needed depends on the water chemistry, temperature, contact period, and whether there is sediment or not. In large scale application, chlorine residue is measured for the right titration in dosage level.
For emergency disinfection, US Environmental Protection Agency recommends the use of 2 drops of 4% to 6% household bleach per liter of water. If the water that is required doesn’t have bleach smell, the bleach can be added more than 2 drops. More people prefer to store drinking water for long term to be used in emergency situation. If you do this, you need to consider following the same protocols of treatment during the storing process (and not when it came to access the water) which usually uses additional level of processing about 15 drops per gallon of water.
You need to make sure that you confirm that the water has the smell of bleach after it left for a half of hour. Besides that, dispose the water and replace it each 3 to 5 years is recommended. All this time, washing the container for foods (usually made of polyethylene) is recommended to use warm soap water or water and bleach solution with strong concentration and followed by flushing it using clean water.
4. Endodontic Therapy
Sodium hypochlorite is also used in endodontic therapy during the treatment for root canal of the teeth. This chemical compound is a perfect choice due to its ability in fighting the pathogen organisms and pulp decay. In the past, Henry Drysdale Dakin solution (0.5%) is used for this treatment. The concentration of sodium hypochlorite that is used in endodontic therapy these days may vary between 0.5% and 5.25%.
In low concentration, this chemical compound will dissolve the necrotic tissue while in higher concentration, the dissolving of tissue is better but also might dissolve vital tissue as well which is the common effect that is not expected. Studies showed that the clinical effectiveness is not increased significantly for concentration that is higher than 1%.
5. Household Bleach Compound
Household bleach and pool chlorination solution are usually stabilized by lye (NaOH) concentration that is significant as the part of its formation reaction. Skin that is exposed to this will experience irritation or burnt due to the elimination of lipid and destruction of tissue. Bleach will be slippery on skin due to this process. Trichloramine is the gas that is used for pool and might cause atopic asthma.
Sodium thiosulfate is an effective chlorine neutralizer. Rinse your skin with 5mg/L solution that is followed with the washing with soap and water immediately will remove the smell of chlorine from your skin. Combining bleach with several household cleaners might be dangerous.
For example, combining cleaner that is made of acid with sodium hypochlorite bleach will create chlorine gas. Combining sodium hypochlorite with ammonia solution (including urine) might create chloramines. The mix of other cleaning material or organic materials with sodium hypochlorite might create gas reaction that might cause acute lung damage. Both chlorine gas and chloramines are toxic. Bleach can react tremendously with hydrogen.
6. The Source of Nucleotide Adenine
Barrette investigated the loss of nucleotide adenine by studying the energy content of cells that are exposed to hypochlorite. It is found that the cells that are exposed to hypochlorite are unable to increase the energy content after the enhancement of nutrients.
The conclusion is that the cells that are exposed lost their ability to control their adenylate pool according to the fact that metabolic intake is just decreased for 45% only after the exposure to hypochlorite and the observation that showed hypochlorite can cause intracellular ATP hydrolysis. This is also confirmed that in the level of bactericide hypochlorite, the cytosolic component is not effective.
It is reported that the modification of several proteins that are bond to the membrane might cause wide scale ATP hydrolysis. This process, together with cells that are unable to remove the AMP from cytosol, will repress the metabolic function. One protein that involves in the loss of ability to reproduce ATP is discovered. This protein is known as ATP synthase.
More Uses of Sodium Hypochlorite
Meanwhile, here are more sodium hypochlorite uses in the general fields.
7. Nerve neutralization material
In various facilities for nervous damage treatment across the US, 50% sodium hypochlorite is used as material for removing all traces of nerve material or dangerous material from PPE (Personal Protective Equipment) after an entry is made by personnel to contagious area. 50% sodium hypochlorite is also used for neutralizing the release of nerve material in contagious area as well. Lower concentration of sodium hypochlorite is used in the same way in Pollution Prevention System (PPS) in order to make sure that there is no nerve material that is released into furnace exhaust.
8. Packaging and Marketing
Whitening agent for household that is sold to be used for washing the clothes is 3-6% sodium hypochlorite solution. The power of this solution is difference from one formulation to another and the power will gradually decrease during storing. The 12% solution is used widely for water chlorination and the 15% solution is commonly used as disinfectant for wastewater in refineries. Sodium hypochlorite also can be used for disinfecting the drinking water as well. This solution also can be found in store shelves as daily sanitation spray.
The household bleach that is used with transfer-phase catalyst is reported can be used to oxidize alcohol in related carbonyl compound. Sodium hypochlorite is a strong oxidator. Oxidation reaction is corrosive. The solution will burn the skin and might cause damage to the eyes, especially when it’s being used in high concentration.
However, according to NFPA, only solution that contains more than 40% of high concentration sodium hypochlorite is considered as dangerous oxidator. Solution with less than 40% of sodium hypochlorite is considered as moderate dangerous oxidator. Chlorination of drinking water might oxidize the organic contaminants that produce trihalomethane (also known as haloform) that no other than carcinogenic substance.
10. Disinfectant Action Mechanism
Escherichia coli that are exposed to sodium hypochlorite will lose its ability to survive in less than 100 ms due to the inactivation of vital system. Sodium hypochlorite can cause 100% detainment of growth just in 5 minutes. However, it’s important to be noticed that the concentration of bactericide that is needed in this process is also very depended on the concentration of bacteria.
The Cautions of the Uses of Sodium Hypochlorite
However, there are many Sodium Hypochlorite uses, you need to pay to these cautions.
1. Glucose Oxidation Blocker
In 1948, Knox was reported the idea of glucose oxidation blocking as the main factor in natural bactericide chlorine solution. He reported that the active ingredient or the diffusion material that penetrates cytoplasm membrane is the key to stop the activity of enzyme that contains sulfhydryl in glycolytic pathway.
This group is also first recorded as the chlorine solution (HOCl) that hampers the sulfhydryl enzyme. Recent studies have been showed that in level of bactericide the cytosol component is not reacted to hypochlorite (HOCl or NaOCl). According to this, McFeters and Camper discovered that aldolase, the enzyme that is suggested by Knox will not be activated, will not be affected by hypochlorite in vivo.
This result showed that the loss of sulfhydryl is not correlated with inactivation. This left a question about what is the cause of the glucose oxidation blocking. The discovery that HOCl can hamper the induction of β-galactosidase by lactose that is added might provide possible answer for this question.
The absorption of substrate that is labeled as radioactive by ATP hydrolysis and the transportation along with proton can be blocked by hypochlorite expose that has been lost its viability before. Hypochlorite (HOCl or NaOCl) plays a role as disinfectant. From this observation, it is suggested that hypochlorite can block the nutrition absorption by disabling the trans-protein. The question about the loss of glucose oxidation is explored even further in the subject of the loss of respiration.
2. Block the DNA Replication
Recently is reported that the bacteria inactivation by hypochlorite occurs due to the blocking of DNA replication. When bacteria are exposed to hypochlorite, there is the deficit of sedimentation in DNA synthesis that precedes the protein synthesis blocking and this is usually occurred reciprocally with the loss of viability.
During genome replication in bacteria, the original replication (ori C in E. coli) that bond to the protein is joined together with cell membrane and this is examined that the treatment with hypochlorite will decrease the affinity of cell membrane that is extracted for ori C and this deficit of affinity is also proportional with the loss of viability.
A study that is conducted by Rosen compared the blocking rate of hypochlorite on plasmid DNA with the different original replication and found out that certain plasmids show the delay in replication blocking when compared to plasmid that contains ori C. Rosen group reported that the inactivation of protein membrane that is involved in DNA replication is action mechanism of hypochlorite.
3. Outspread Protein and Aggregation
Hypochlorite is known cause post-translation change in protein, except cysteine oxidation and methionine. A test to the role of hypochlorite bactericide reveals that it is a potential inductor from protein aggregation. Hsp33, a molecular chaperone, is known activated by the post-oxidative tension, is protecting bacteria from the effect of hypochlorite by acting as a holdase which effectively prevent the coagulation of protein.
Strains from E. coli and Vibrio cholerae are lack of Hsp33, especially the ones that are sensitive to hypochlorite. Hsp33 is protected by many essential proteins from aggregation and inactivation due to hypochlorite which is a possibility of mediator from the effect of hypochlorite bactericide.
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