Calcium chloride (chemical formula: CaCltwo）It is a white or yellowish solid inorganic compound, belonging to salt, and is a typical ionic halide. It is widely used in many fields due to its high solubility, hygroscopicity and dehydration.According to its hydration form, it exists in different physical forms, and the most common is dihydrate (CaCltwo·2HtwoO），Its high solubility enables it to dissolve rapidly in water, releasing a lot of heat, so it is very useful in applications requiring rapid heating or drying.In addition, calcium chloride is also often used in brine, road deicing agent and desiccant used in refrigeration equipment.
Chinese name
calcium chloride
Foreign name
Calcium chloride
Alias
Anhydrous calcium chloride
chemical formula
CaCltwo
molecular weight
one hundred and ten point nine eight four
CAS login number
10043-52-4[1]
EINECS login number
233-140-8[1]
Melting point
772 ℃[1]
Boiling point
1600 ℃[1]
Water solubility
Easily soluble in water, exothermic when dissolved
Colorless cubic crystal, white or grayish white, in granular, honeycomb block, spherical, irregular granular and powder forms.Slightly toxic, odorless, slightly bitter.It is easily deliquescent when exposed to air.Easily soluble in water, the solubility is 74.0 g/100 g water at 20 ℃, and a large amount of heat is released at the same time (the dissolution enthalpy of calcium chloride is - 176.2 cal/g).This property makes it very useful in applications requiring rapid heat generation, for example, as a heat source in some heating processes. In addition, the specific heat capacity and thermal conductivity of calcium chloride are also important physical parameters, affecting its efficiency in thermal management and regulation applications[24-25]。The calcium chloride aqueous solution is neutral.It is easily soluble in a variety of polar and proton solvents. Solubility (g/100mL solvent) in the following solvents at 20 ℃: methanol: 29.2, absolute ethanol: 25.8, n-propanol: 15.8, n-butanol: 25.0, n-pentanol: 11.5, ethylene glycol: 21.6 (25 ℃), formic acid: 43.1, acetic acid: 15.0 (30 ℃), hydrazine: 16.0.However, in dipolar solvents and low polar solvents, such as ether, tetrahydrofuran, etc., it is only slightly soluble or insoluble.React with ammonia or ethanol to generate CaCl respectivelytwo·8NHthreeAnd CaCltwo·4CtwoHfiveOH complex.The solution crystallizes at low temperature and precipitates hexahydrate. When it is gradually heated to 30 ℃, it will dissolve in its own crystal water. After continuous heating, it will gradually lose water. When it is heated to 200 ℃, it will become dihydrate. When it is heated to 260 ℃, it will become white porous anhydrous calcium chloride.Some hydrolysis reaction occurs during heating and dehydration of hydrated calcium chloride, so the product often contains a small amount of CaO impurities[2-3]。
Figure 1 Calcium Chloride Cell
chemical property
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Electrolyte properties
In aqueous solution, calcium chloride is completely ionized into Ca ²+and Cl ⁻ ions, showing the characteristics of strong electrolyte.This electrolyte property enables calcium chloride solution to become an important chemical raw material and analytical reagent while having high conductivity and being able to conduct current effectively.In the fields of water treatment, metal processing and chemical synthesis, the use of this property of calcium chloride can effectively carry out ion exchange, pH adjustment and metal ion precipitation.
Reactions with other chemicals
Calcium chloride can also react with sodium sulfate (NatwoSOfour）Double substitution reaction takes place for other salts to generate sodium chloride and calcium sulfate precipitation.The characteristics of this chemical reaction have important applications in industrial production and laboratory analysis, such as the adjustment of water hardness or the use of precipitation agent.
antidote
The pH value of 5% aqueous solution is 4.5~9.2.1.7% aqueous solution is isotonic with serum.This product is made from calcium carbonate and hydrochloric acid, and is an antidote for magnesium poisoning[4]。Calcium ions can form insoluble calcium fluoride with fluoride, which can be used to rescue fluorosis.
Chemical reaction equation
Calcium chloride with higher solubility can undergo double decomposition reaction to generate precipitation with lower solubility:
The calcium chloride dihydrate is dried and dehydrated at 200~300 ℃ to obtain the edible anhydrous calcium chloride product.
Spray drying dehydration
The refined neutral calcium chloride solution, which has removed arsenic and heavy metals, is sprayed from the top of the spray drying tower through a nozzle into a mist, and is dried and dehydrated by countercurrent contact with the 300 ℃ hot air flow to obtain powdered anhydrous calcium chloride, which is used to prepare edible anhydrous calcium chloride products.
By products of chlor alkali industry
Chlor alkali wastewater, which contains many organic and inorganic substances, including sodium chloride, calcium chloride, magnesium chloride, etc., can be produced by special processes and technologies.[19]
Complex decomposition method
It is made from calcium carbonate (limestone) and hydrochloric acid.
Chemical reaction equation: CaCOthree+2HCl=CaCltwo+HtwoO+COtwo↑。
After the above steps are completed, heat to 260 ℃ and evaporate for dehydration.
Refining process
The by-product from the production of sodium hypochlorite is refined.
It is refined from the by-product of Solvay method for preparing sodium carbonate.
Prepare 10% sample solution (calculated by anhydrous calcium chloride CaCl2), and its calcium (IT-10) and chloride (IT-12) tests are positive.
Content analysis
Take about 1.5 g of the sample (or about 1 g of the sample if it is anhydrous calcium chloride), weigh it accurately, transfer it into a 250 mL volumetric flask, dissolve it with a mixture of 100 mL water and 5 mL dilute hydrochloric acid test solution (TS-117), and mix it with water to a constant volume.Take 50.0mL of this solution and put it into a suitable container, add 50mL of water, add about 30mL of 0.05 mol/L EDTA disodium solution from a 50mL buret under stirring (preferably mechanical stirring), then add 15mL of sodium hydroxide test solution (TS-224) and 300mg of hydroxynaphthol blue indicator, and continue to drip until blue color is generated.0.05 mol/L EDTA disodium solution per ml is equivalent to CaCltwo·2HtwoO 7.551mg。If it is anhydrous calcium chloride, 0.05mol/L EDTA disodium solution per milliliter is equivalent to CaCltwo5.550mg[18]。Main applications
Industrial use
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1. It is used as a multi-purpose desiccant, such as drying of nitrogen, oxygen, hydrogen, hydrogen chloride, sulfur dioxide and other gases.It is used as dehydrating agent in the production of alcohol, ester, ether and acrylic resin.Calcium chloride aqueous solution is an important refrigerant for refrigerator and ice making. It can accelerate the hardening of concrete and increase the cold resistance of building mortar. It is an excellent building antifreeze.It is used as port fog suppressant, road dust collector and fabric fire retardant.Used as protective agent and refining agent for aluminum magnesium metallurgy.It is a precipitant for producing lake pigments[26]。Used for deinking of waste paper processing.It is the raw material for calcium salt production.
3. It is used as desiccant, road dust collector, defogger, fabric fire retardant, food preservative and calcium salt manufacturing.
4. Used as lubricant additive.
5. Used as analytical reagent.
6. It is mainly used to treat tetany, urticaria, exudative edema, colic in intestines and ureters, and magnesium poisoning caused by low blood calcium.
7. It is used as calcium strengthening agent, curing agent, chelating agent and desiccant in the food industry.
8. It can increase the permeability of bacterial cell wall[2]。
Medical use
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indication
1. This product can be used for colic, etc.
2. It can be used for itchy skin diseases.
3. It is used to rescue magnesium salt poisoning.
4. For vitamin D deficiency rickets, rickets, pregnant women and lactating women calcium salt supplement.
5. To treat tetany and vitamin D deficiency caused by calcium deficiency, acute hypocalcemia, alkalosis and hypoparathyroidism;
6. Allergic disease;
7. Rescue of magnesium poisoning;
8. Rescue of fluorosis;
9. Use during cardiac resuscitation, such as rescue of cardiac dysfunction caused by hyperkalemia, hypocalcemia, or calcium channel block.
10. Calcium chloride solution can induce polymerization of actin monomer, and the critical concentration for polymerization of actin monomer is inversely related to the concentration of calcium chloride solution.The specific mechanism of the induced polymerization of actin is related to the binding of calcium ions to multiple specific sites of the protein.[28]
Dosage and usage
Dilute 10-20mL of 5% calcium chloride solution and 25% glucose solution twice before intravenous injection [28].
matters needing attention
1. During intravenous injection, the whole body may feel hot.The injection should be slow (no more than 2mL per minute). Because calcium salt excites the heart, too fast injection will suddenly increase the blood calcium concentration, causing arrhythmia, even cardiac arrest.
2. Do not use this product during the application of cardiac glycosides or within 7 days after drug withdrawal.
3. It is strongly irritant, and 5% solution cannot be directly injected intravenously. It should be diluted with the same amount of glucose solution before injection.It is also not suitable for skin injection or intramuscular injection.
4. The injection shall not leak out of the blood vessel, or it will cause severe pain and tissue necrosis.In case of extravascular leakage, 5% procaine solution shall be used for local sealing immediately.
5. Dosage for children: 25 mg/kg (6.8 mg calcium) for low calcium, intravenous drip slowly.
Intravenous injection may cause systemic fever, and too fast intravenous injection may cause nausea, vomiting, arrhythmia and even cardiac arrest.Hypercalcemia can be manifested as constipation, drowsiness, persistent headache, loss of appetite, metallic taste in the mouth, abnormal dry mouth, etc. in the early stage, and mental disorder, hypertension, light sensitivity of eyes and skin, nausea in the late stage.
In biological and medical research, calcium chloride is widely used to prepare buffer solution for biomedical experiments, such as adding CaCl when researching a new activator for potassium ion channel complextwoPrepare ND96 stock solution for separated oocytes;When studying the function of guanylyl cyclase C on midbrain dopamine neurons, CaCl2 was used to prepare brain slices;When studying the fluororibose switch used to resist fluoride toxicity in bacteria and archaea, the series labeling experiment was carried out with 1mmol/L CaCl2.
In the process of introducing the target gene into the receptor cell, calcium chloride can be used to increase the permeability of the receptor cell membrane, making it easier to import the plasmid. This method was discovered by Stanford University geneticist Stanley Norman Cohen when he studied E. coli in 1972.
Intravenous injection of 10% calcium chloride solution can be used to treat hypocalcemia, and calcium chloride can also be used to treat magnesium poisoning.It was found that injection of calcium chloride solution could antagonize cardiac toxicity through ECG measurement.In the case of high serum potassium concentration caused by hyperkalemia, calcium chloride can protect the myocardial layer and prevent arrhythmia.As a regular drug in the emergency room of American hospitals, calcium chloride can be used for rapid treatment of calcium channel blocker poisoning (this kind of poisoning can be caused by the side effects of taking the drug diltiazem to prevent heart disease) and poisoning caused by hydrofluoric acid, but it has no effective detoxification effect on poisoning caused by black widow spider bite.Calcium chloride sodium bromide injection is approved by the State Food and Drug Administration to be used as a water electrolyte regulator in China.
desiccant
The strong moisture absorption capacity of calcium chloride makes it an ideal desiccant in the manufacturing process, which is used to protect goods from moisture damage, especially when transporting and storing sensitive substances[22-23]。Granular anhydrous calcium chloride is often used as a desiccant to fill the drying tube. Giant algae (or sea grass ash) dried with calcium chloride can be used in the production of soda ash.Some household dehumidifiers use calcium chloride to absorb moisture in the air.Calcium chloride can also be used as a desiccant or dehydrating agent for gases and organic liquids.Since calcium chloride is neutral, it can dry acidic or alkaline gases and organic liquids, and can also dry these produced gases when making a small amount of gases in the laboratory, such as nitrogen, oxygen, hydrogen, hydrogen chloride, sulfur dioxide, carbon dioxide, nitrogen dioxide, etc.However, it cannot be used to dry ethanol and ammonia, because ethanol and ammonia will react with calcium chloride to form alcohol compound CaCltwo·4CtwoHfiveOH and ammonia compound CaCltwo·8NHthree。Anhydrous calcium chloride can also be made into household products and used as an air hygroscopic agent. Anhydrous calcium chloride has been approved by FDA as an hygroscopic agent for first-aid dressing. Its role is to ensure the dryness of the wound.
The anhydrous calcium chloride is spread on the gravel pavement, and the moisture in the air is condensed when the air humidity is lower than the dew point by using the hygroscopicity of anhydrous calcium chloride to keep the road surface wet, so as to control the dust rising on the road.
Deicing agent and coolant
Calcium chloride can reduce the freezing point of water. Spreading calcium chloride hydrate on the road can prevent icing, deicing and snow melting, but the salt water after the melting of ice and snow will damage the soil and vegetation along the road and deteriorate the pavement concrete.
Calcium chloride solution can also be mixed with dry ice to prepare a low-temperature cooling bath.Add the stick shaped dry ice into the brine solution in batches until ice blocks appear in the system.The stable temperature of the cooling bath can be maintained by different kinds and concentrations of salt solutions.Generally, calcium chloride is commonly used as salt raw material, and the required stable temperature is obtained by adjusting the concentration, not only because calcium chloride is cheap and easy to obtain, but also because the eutectic temperature of calcium chloride solution (that is, the temperature when the solution is completely condensed to form granular ice salt particles) is quite low, reaching - 51.0 ℃, which makes the adjustable temperature range from 0 ℃ to - 51 ℃.This method can be realized in a dewar bottle with heat preservation effect, or a general plastic container can be used to hold the cooling bath when the dewar bottle is limited in volume and more salt solution needs to be prepared at the same time. In this case, the temperature is also relatively stable.
Source of calcium ion
Adding calcium chloride to the swimming pool water can make the pool water become a pH buffer solution and increase the hardness of the pool water, which can reduce the erosion of the pool wall concrete.According to Le Chatelier's principle and the same ion effect, increasing the concentration of calcium ions in the pool water will slow down the dissolution of calcium compounds essential to the concrete structure.
Adding calcium chloride to the water of the marine aquarium can increase the content of calcium available to the organisms in the water. Molluscs and coelenterates bred in the aquarium will use it to form calcium carbonate shells.Although the same purpose can be achieved with calcium hydroxide or calcium reactor, adding calcium chloride is the fastest method and has the smallest impact on the pH value of water.
food
As a food ingredient, calcium chloride can act as a multivalent chelating agent and curing agent. It has been approved by the European Union for use as a food additive, and its E code is E509.It is considered by the US Food and Drug Administration as "generally recognized as safe substance".
Calcium chloride can be used as curing agent for canned vegetables.It can also solidify the soybean curd to form tofu, and can also be used as the raw material for cooking molecular food to gelatinize the surface of vegetable and fruit juice to form caviar like pellets by reacting with sodium alginate.Add to sports drinks or some soft drinks including bottled water as an electrolyte.Because calcium chloride has a very strong salty taste, it can replace salt in the production of pickled cucumbers without increasing the sodium content of food.Calcium chloride's ability to reduce freezing point is used to slow the freezing of caramel in chocolate bars filled with caramel.
Calcium chloride will be added to the beer brewing liquid lacking minerals, because calcium ion is one of the most influential minerals in the beer brewing process, which will affect the acidity of wort and the role of yeast.Moreover, calcium chloride can bring sweetness to the brewed beer.
other aspects
Hydrated calcium chloride solid can be used as phase change energy storage material.For example, because the melting point of calcium chloride hexahydrate is 30 ℃, and the melting heat (i.e. the heat absorbed during the transformation of substances from solid phase to liquid phase at the same temperature) reaches 190 kJ/mol, it can be used as a medium low temperature for industrial waste heat recovery and the absorption and utilization of solar radiation heat. However, like all inorganic hydrated salt phase change materials, it has a serious problem of supercooling (its supercooling degree reaches 20 ℃)It needs to add nucleating agent to overcome.
Calcium chloride plays a role in accelerating the initial setting in concrete, but chloride ion will cause corrosion of reinforcement, so calcium chloride cannot be used in reinforced concrete.Anhydrous calcium chloride can provide a certain degree of moisture for concrete due to its hygroscopicity.
Calcium chloride is also an additive in plastics and fire extinguishers. It is used as a filter aid in wastewater treatment and as an additive in blast furnace to control the aggregation and adhesion of raw materials so as to avoid the settlement of furnace burden. It acts as a diluent in fabric softener.
The exothermic nature of calcium chloride dissolution makes it used in self heating cans and heating pads.
In the petroleum industry, calcium chloride is used to increase the density of solid free brine, and can also be added to the water phase of emulsified drilling fluid to inhibit the expansion of clay.As a flux, it plays a role in reducing the melting point in the process of producing sodium metal by electrolytic melting sodium chloride with David method.When making ceramics, calcium chloride will be used as one of the material components, which will make clay particles suspend in the solution, so it is easier to use clay particles during grouting.matters needing attention
Hazard Overview
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Invasion route: dust inhalation, ingestion
Health hazard: dust can burn and stimulate the nasal cavity, mouth and throat, and can also cause epistaxis and damage nasal tissue;Dry powder may irritate skin, and solution may severely irritate or even burn skin
Skin contact: Take off contaminated clothes and wash with plenty of flowing water.
Eye contact: Lift the eyelid and flush with flowing water or physiological saline.Get medical attention.
Inhalation: leave the site to fresh air.If breathing is difficult, give oxygen.Get medical attention.
Ingestion: drink enough warm water to induce vomiting.Get medical attention.
Hypercalcemia caused by medical injection: cardiac arrest.
Emergency Management
Isolate the leakage contaminated area and restrict access.Avoid flying dust, carefully sweep it up, put it in a bag and transfer it to a safe place or transport it to a waste disposal site for disposal.
Operation precautions
Close operation and strengthen ventilation.Operators must be specially trained and strictly abide by the operating procedures.It is recommended that operators wear self-priming filter type dust masks to avoid dust generation.Load and unload gently during transportation to prevent damage to packaging and containers.
Precautions for storage
Store in a cool and ventilated warehouse.The packaging container must be sealed to prevent moisture.Stack separately from deliquescent articles.
Relevant limit
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1. GB 2760-96: Coagulants for canned and bean products, GMP; processing aids.
GB 2760-2001: Soft drinks 0.44 ～ 3.7 g/kg;Mixed water 100mg/L (36 mg/L as Ca).
2. FAO/WHO (1984, mg/kg) food additive: canned tomatoes, 800 pieces, 450 whole packs (calculated by Ca);Grape canned 350 (calculated by Ca);Canned green peas, strawberries, fruit salad, etc. 350 (calculated by Ca);Canned ripe peas 350 (calculated by Ca);Jam and jelly 200 (calculated by Ca);Low power concentrated milk, sweet condensed milk and thin cream, 2 g/kg for single use and 3 g/kg for combined use with other stabilizers (anhydrous);Milk powder and cream powder 5 g/kg (anhydrous);Pickled cucumber 250;Generally, cheese is 200% of the milk used.
3. GB 14880-94: As a nutritional fortifier, it is the same as "01202, calcium glycerophosphate".
4. FDA, § 184.1193 (2000): Baked food, dairy products 0.3%;Non alcoholic beverage and beverage stock 10.22%;0.2% cheese, processed fruit and juice, gravy and sauce;Coffee and tea 0.3294;Sugar food products 0.4%;Jam and jelly 0.1%;0.25% meat products;Plant protein products 2.0%;0.4% of processed vegetable juice;Other food 0.05%.
5. USDA, 9CFR, § 381.7, § 381.147 (2000): protease solution used for dipping or injecting raw meat, ≤ 3% by weight of untreated raw materials.
6. Soak fruits and vegetables with calcium chloride solution. After sterilization, the fruits and vegetables have good crispness and color protection effect.For example, it is used for canned foods such as apples, packaged tomatoes, assorted vegetables, winter melon, etc.[18]
toxicology
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Calcium chloride is irritant because it can dehydrate wet skin. When solid anhydrous calcium chloride is dissolved, it gives off a lot of heat. If it is accidentally ingested, it can cause burns to the mouth and esophagus.Ingestion of concentrated solution or solid calcium chloride may cause gastrointestinal irritation or ulcer[20]。
