Calcium chloride is a salt formed by chloride ions and calcium ions. Anhydrous calcium chloride has a strong moisture absorption, used as a desiccant for various substances, in addition to road dust, soil improver, refrigerant, water purification agent, paste agent. It is a widely used chemical reagent, pharmaceutical raw materials, food additives, feed additives and raw materials for the manufacture of metal calcium.
Physical properties of calcium chloride
Calcium chloride is colorless cubic crystal, white or off-white, granular, honeycomb block, spheroid, irregular granular, powdered. Melting point 782°C, density 1.086 g/mL at 20 °C, boiling point 1600°C, water solubility 740 g/L. Slightly toxic, odorless, slightly bitter taste. Extremely hygroscopic and easily deliqued when exposed to air.
Easily soluble in water, while releasing a large amount of heat (calcium chloride dissolution enthalpy of -176.2cal/g), its aqueous solution is slightly acidic. Soluble in alcohol, acetone, acetic acid. Reacting with ammonia or ethanol, CaCl2·8NH3 and CaCl2·4C2H5OH complexes were formed, respectively. At low temperature, the solution crystallizes and precipitates as a hexahydrate, which is gradually dissolved in its own crystalline water when heated to 30 ° C, and gradually loses water when heated to 200 ° C, and becomes a dihydrate when heated to 260 ° C, which becomes a white porous anhydrous calcium chloride.
Anhydrous calcium chloride
1, physical and chemical properties: colorless cubic crystal, white or off-white porous block or granular solid. The relative density is 2.15, the melting point is 782℃, the boiling point is above 1600℃, the hygrhygability is very strong, easy to delix, easy to dissolve in water, while releasing a lot of heat, odorless, slightly bitter taste, the aqueous solution is slightly acidic, soluble in alcohol, acrylic vinegar, acetic acid.
2, product use: It is a precipitating agent for the production of color lake pigments. Production of nitrogen, acetylene gas, hydrogen chloride, oxygen and other gas desiccant. Alcohols, ethers, esters and acrylic resins are used as dehydrating agents, and their aqueous solutions are important refrigerants for refrigerators and refrigeration. It can accelerate the hardening of concrete, increase the cold resistance of cement mortar, and is an excellent antifreeze agent. Used as a protective agent for aluminum magnesium metallurgy, refining agent.
Flake calcium chloride
1, physical and chemical properties: colorless crystal, this product is white, off-white crystal. Bitter taste, strong deliquescent.
Its relative density is 0.835, easily soluble in water, its aqueous solution is neutral or slightly alkaline, corrosive, soluble in alcohol and insoluble in ether, and dehydrated into anhydrous matter when heated to 260℃. Other chemical properties are similar to anhydrous calcium chloride.
2, function and use: flake calcium chloride used as refrigerant; Antifreeze agent; Molten ice or snow; Flame retardants for finishing and finishing cotton fabrics; Wood preservatives; Rubber production as a folding agent; Mixed starch is used as a gluing agent.
Calcium chloride aqueous solution
Calcium chloride solution has the characteristics of conductivity, lower freezing point than water, heat dissipation in contact with water, and has better adsorption function, and its low freezing point can be used in a variety of industrial manufacturing and public places.
The role of calcium chloride solution:
1. Alkaline: Calcium ion hydrolysis is alkaline, and hydrogen chloride is volatile after chloride ion hydrolysis.
2, conduction: there are ions in the solution that can move freely.
3, freezing point: calcium chloride solution freezing point is lower than water.
4, boiling point: calcium chloride aqueous solution boiling point is higher than water.
5, evaporation crystallization: calcium chloride aqueous solution evaporation crystallization to be in an atmosphere full of hydrogen chloride.
Desiccant
Calcium chloride can be used as a desiccant or dehydrating agent for gases and organic liquids. However, it cannot be used to dry ethanol and ammonia, because ethanol and ammonia react with calcium chloride to form alcohol complex CaCl2·4C2H5OH and ammonia complex CaCl2·8NH3, respectively. Anhydrous calcium chloride can also be made into household products used as an air hygroscopic agent, anhydrous calcium chloride as a water absorption agent has been approved by the FDA for dressing first aid, its role is to ensure the dryness of the wound.
Because calcium chloride is neutral, it can dry acidic or alkaline gases and organic liquids, but also in the laboratory to make a small amount of gases such as nitrogen, oxygen, hydrogen, hydrogen chloride, sulfur dioxide, carbon dioxide, nitrogen dioxide, etc., when drying these produced gases. Granular anhydrous calcium chloride is often used as a desiccant to fill drying pipes, and giant algae (or seaweed ash) dried with calcium chloride can be used for the production of soda ash. Some household dehumidifiers use calcium chloride to absorb moisture from the air.
The anhydrous calcium chloride is spread on the sandy road surface, and the hygroscopic property of anhydrous calcium chloride is used to condense the moisture in the air when the air humidity is lower than the dew point to keep the road surface wet, so as to control the dust on the road.
Deicing agent and cooling bath
Calcium chloride can lower the freezing point of water, and spreading it on roads can prevent freezing and deicing snow, but the salt water from melting snow and ice can damage soil and vegetation along the road and deteriorate the pavement concrete. Calcium chloride solution can also be mixed with dry ice to prepare a cryogenic cooling bath. Stick dry ice is added to the brine solution in batches until ice appears in the system. The stable temperature of the cooling bath can be maintained by different kinds and concentrations of salt solutions. Calcium chloride is generally used as a 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 all condensed to form granular ice salt particles) is quite low, which can reach -51.0 ° C, so that the adjustable temperature range is from 0 ° C to -51 ° C. This method can be realized in Dewar bottles with insulation effect, and can also be used in general plastic containers to hold cooling baths when the volume of Dewar bottles is limited and more salt solutions need to be prepared, in which case the temperature is also more stable.
As a source of calcium ions
Adding calcium chloride to swimming pool water can make the pool water a pH buffer and increase the hardness of the pool water, which can reduce the erosion of the concrete wall. According to Le Chatelier’s principle and the isoionic effect, increasing the concentration of calcium ions in the pool water slows down the dissolution of calcium compounds that are essential for concrete structures.
Adding calcium chloride to the water of Marine aquariums increases the amount of bioavailable calcium in the water, and mollusks and coelintestinal animals raised in aquariums use it to form calcium carbonate shells. Although calcium hydroxide or a calcium reactor can achieve the same purpose, adding calcium chloride is the fastest method and has the least effect on the pH of the water.
Calcium chloride for other uses
The dissolving and exothermic nature of calcium chloride makes it used in self-heating cans and heating pads.
Calcium chloride can help speed up the initial setting in concrete, but chloride ions can cause corrosion of steel bars, so calcium chloride cannot be used in reinforced concrete. Anhydrous calcium chloride can provide a certain degree of moisture to concrete because of its hygroscopic properties.
In the petroleum industry, calcium chloride is used to increase the density of solid-free brine, and can also be added to the aqueous phase of emulsified drilling fluids to inhibit the expansion of clay. It is used as a flux to lower the melting point in the process of producing sodium metal by electrolytic melting of sodium chloride by the Davy process. When ceramics are made, calcium chloride is used as one of the material components, which will allow clay particles to be suspended in the solution, so that the clay particles are easier to use when grouting.
Calcium chloride is also an additive in plastics and fire extinguishers, as a filter aid in wastewater treatment, as an additive in blast furnaces to control the aggregation and adhesion of raw materials to avoid the settlement of the charge, and as a diluent in fabric softeners.
Post time: Mar-19-2024
