The calcium hypochlorite is an inorganic compound of formula Ca (ClO) 2. It is a salt marketed as granules or tablets. It decomposes easily in water releasing oxygen and chlorine. It has a strong smell of chlorine and sIt is mainly used as a bleaching or disinfecting agent. Its structure is presented in figure 1.
The calcium hypochlorite production process basically consists of a reaction of hydrated lime (calcium hydroxide) with gaseous chlorine by chlorination of a suspension of lime and caustic soda with subsequent precipitation of calcium hypochlorite dihydrate, dried under vacuum (Lewis, 2007).
The reaction is: 2Cl2 + 2Ca (OH) 2 → Ca (OCl) 2 + CaCl2 + 2H2O.
Powdered bleach is not a simple mix of calcium hypochlorite, calcium chloride, and calcium hydroxide. Rather, a mixture consisting primarily of calcium hypochlorite Ca (OCl) 2, dibasic calcium hypochlorite, Ca3 (OCl) 2 (OH) 4, and dibasic calcium chloride, Ca3Cl2 (OH) 4. It is made from slightly damp slaked lime.
Physical and chemical properties
Calcium hypochlorite is a white granular solid that is often commercially compressed into tablets and has a characteristic chlorine odor (National Center for Biotechnology Information, 2017). Its appearance is illustrated in figure 2 (kingnod, 2015).
The compound has a molecular weight of 142.98 g / mol and a density of 2.35 g / ml. It has a melting point of 100 ° C and a boiling point of 175 ° C where it begins to decompose (Royal Society of Chemistry, 2015).
The compound is soluble in water, being able to dissolve 21 grams for every 100 ml of this solvent. It also reacts with alcohols, oxidizing them to their respective carboxylic acids.
Calcium hypochlorite is a powerful oxidizing agent, particularly in aqueous media and by decomposing when heated to release oxygen and chlorine gases. May react explosively with finely divided carbon. Reacts with acetylene to form explosive chloroacetylenes.
Reaction with alcohols can lead to explosions. Reactions with nitromethane, methanol, ethanol (and other alcohols) can become violent after a while. Reacts with possible ignition and / or explosion with organic sulfur compounds and sulfides.
It breaks down the evolution of oxygen, a change that can be catalyzed by rust in metal containers. Highly explosive NCl3 forms in contact with urea or ammonia. Evolves highly toxic gaseous chlorine gas when heated or in contact with acids.
Reacts violently with a mixture of wet sulfur expelling molten sulfur. The combination of calcium hypochlorite, sodium hydrogen sulfate, starch and sodium carbonate. When it is compressed, it causes the incandescence of materials, followed by an explosion (calcium hypochlorite, 2016).
Reactivity and hazards
Calcium hypochlorite is an unstable compound classified as a strong oxidizing agent. It is corrosive and irritant in case of contact with the skin, in contact with the eyes and in case of ingestion. It is also very dangerous in case of inhalation.
The chemical product has properties (corrosive effects and acute respiratory toxicity) that indicate a danger to human health.
Although there are some open uses, consumer exposure is sufficiently regulated under the laws of drinking water and other water-related activities and occupational exposure is adequately controlled in the sponsoring country to ensure safe handling (CALCIUM HYPOCHLORITE, 2016).
In case of contact with the eyes, check if you are wearing contact lenses and remove them immediately.
Eyes should be flushed with running water for at least 15 minutes, keeping the eyelids open. Cold water can be used. Eye ointment should not be used.
If the chemical comes into contact with clothing, remove it as quickly as possible, protecting your own hands and body.
Place the victim under a safety shower. If the chemical accumulates on the victim’s exposed skin, such as hands, the contaminated skin is gently and carefully washed with running water and non-abrasive soap.
The acid can also be neutralized with dilute sodium hydroxide or a weak base such as baking soda. If irritation persists, seek medical attention. Wash the contaminated clothing before using it again.
If the contact with the skin is severe, it should be washed with a disinfectant soap and cover the contaminated skin with an antibacterial cream.
In case of inhalation, the victim should be allowed to rest in a well-ventilated area. If inhalation is severe, the victim should be evacuated to a safe area as soon as possible. Loosen tight clothing such as a shirt collar, belt, or tie.
If it is difficult for the victim to breathe, oxygen should be administered. If the victim is not breathing, mouth-to-mouth resuscitation is performed.
Always taking into account that it can be dangerous for the person providing aid to give mouth-to-mouth resuscitation, when the inhaled material is toxic, infectious or corrosive.
In case of ingestion, do not induce vomiting. Loosen tight clothing such as shirt collars, belts, or ties. If the victim is not breathing, perform mouth-to-mouth resuscitation.
In all cases, immediate medical attention should be sought (National Institute for Occupational Safety and Health, 2015).
The main use for calcium hypochlorite is as a water bleach and disinfectant (Calcium Hypochlorite: A Pool Chemical And Much More, SF). The compound is added as a granule or tablet to pool water to kill germs that can make swimmers sick.
Used correctly, by well-trained pool operators, this compound destroys germs that are capable of causing numerous health problems for pool users.
Some of these are diarrhea, swimmer’s ear (an unpleasant earache), and various respiratory, skin, and wound infections. Hot springs and whirlpools are also disinfected with calcium hypochlorite.
Its advantage when compared with sodium hypochlorite is that, due to its stoichiometric ratio, it has a higher chlorine content, 65 to 70% higher than its sodium analog (3v-tech, 2017).
The compound is also used as an algaecide, bactericide, deodorant, disinfectant, fungicide and in sugar refining.
Calcium hypochlorite is a general oxidizing agent and therefore finds some use in organic chemistry. For example, the compound is used to cleave glycols, α-hydroxycarboxylic acids, and keto acids. Also to produce aldehydes or fragmented carboxylic acids.
Calcium hypochlorite can also be used in haloform reaction to make chloroform based on the reaction:
3Ca (ClO) 2 + 2 (CH3) 2CO → 2CHCl3 + 2Ca (OH) 2+ Ca (CH3COO) 2
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5. kingnod. (2015). Calcium hypochlorite. Recovered from ikingnod.com.
6. Lewis, RS (2007). Hawley’s Condensed Chemical Dictionary 15th Edition. New York: John Wiley & Sons, Inc.
7. National Center for Biotechnology Information. (2017, April 15). PubChem Compound Database; CID = 24504. Recovered from PubChem.
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