Chemical properties
It appears as white cubic crystalline powder. Industrial products often contain magnesia, alumina and ferric oxide and other impurities so exhibit dark gray, light yellow or brown. It is soluble in acid.
Uses
1. Calcium oxide can be used in the manufacture of calcium carbide, soda ash, bleaching powder, used as building materials, refractoriness’, desiccant and soil conditioner and calcium fertilizer
2. It can be used as an analysis reagent and flux agent for manufacturing fluorescence powder.
3. It can be used in the manufacture of calcium carbide, soda ash, bleaching powder, also used for leather, waste water purification
4. Calcium oxide can be used as building materials, metallurgical flux agent and the major raw materials for the manufacturing of calcium hydroxide and a variety of calcium compounds. It is also the inexpensive alkali in the chemical industry. It is widely used in pesticides, paper, food, petrochemical, leather, waste water purification and so on. It can also be used for the drying of the laboratory ammonia and alcohol dehydration.
5. Use as drug carriers.
6. Uses as analysis reagents; Calcium oxide can be applied to steel, pesticides, pharmaceuticals, non-ferrous metals, fertilizers, leather and manufacturing of calcium hydroxide, drying of laboratory ammonia, carbon dioxide absorbent and alcohol dehydration.
Content analysis
Approximately 1 g of the sample was burned to constant weight (accurately weighed) and dissolved in 20 ml of dilute hydrochloric acid solution (TS-117). After cooling, dilute to 500.0ml with water and mix uniformly. Take 50 mL of this solution into the appropriate container, add 50ml of water. Add 30 mL 0.05ml/L disodium EDTA via a 50 mL burette with stirring (preferably with a magnetic stirrer); further add 15ml sodium hydroxide solution (TS-224) and hydroxy naphthol blue indicator (300 mg) for continue titration to the blue end. Per ml of 0.05 mol/L of EDTA corresponds to 2.804 mg of calcium oxide.
Identification test
1 g of the sample was shaken with 20 ml of water, and the acetic acid test solution (TS-1) was added to dissolve the sample. The calcium test (IT-10) of this solution was positive.
Toxicity
ADI is not subject to restrictive regulations (FAO/WHO, 2001).
GRAS (FDA, §18.5210; §184.12l0, 2000);
See Calcium Oxide.
It can stimulate the mucous membrane, causing sneezing, in particular, can cause fat saponification so the water will be absorbed by the skin, dissolving the protein with stimulating and corroding the tissue. It has strong effect against the eye mucosa, being able cause oral and nasal mucosa superficial ulcers, and sometimes there may be perforation of the nasopharyngeal diaphragm, deep respiratory tract disease. Inhalation of lime dust may cause pneumonia.
In case of inhalation of dust, it can be treated via inhaling water vapor (add some of the citric acid crystals to the water in advance) and coat the mustard cream in the chest. If falling into the eyes, we can open up the eyes and immediately rinse with running water for 10~30 min and then rinse with 5% ammonium chloride solution. When the skin burns, it can be used with 5% citric acid, tartaric acid, acetic acid or salt solution of mineral oil or vegetable oil to remove the lime residue sticking to the skin.
The maximum allowable concentration in the United States is 5 mg/m3.
During operation, it should be paid attention to the protection of respiratory organs. Wear uniforms manufactured using dust-proof fiber, gloves and closed dust-proof glasses. Coat the ointment-containing grease. Clean after work. During the preparation and application, it should be prevented of dust inhalation.
Production method
Calcium carbonate calcination first apply calcium carbonate for reaction with hydrochloric acid to generate calcium chloride, followed by addition of ammonia for neutralization, standing for precipitation and filtration, followed by adding sodium bicarbonate for reaction to generate calcium carbonate precipitate. It is further subject to centrifugal separation dehydration, drying and calcination, followed by crushing and screening to obtain the finished product of medicinal calcium oxide. Its reaction is:
CaCO3 + 2HCl → CaCl2 + CO2 + H2O
CaCl2 + 2NH3? H2O? Ca (OH) 2 + 2NH4Cl
Ca (OH) 2 + NaHCO3 → CaCO3 + NaOH + H2O
CaCO3 [△]→CaO + CO2 ?.
Limestone calcination method: crush the coarse limestone to 150 mm, and screen for the fine residue below 30 to 50 mm. Anthracite or coke required a particle size to be below 50 mm, which contains not too much low melting point ash content. The amount of anthracite or coke is 7.5% to 8.5% of that of limestone by weight. The selected limestone and fuel are timely and quantitatively supplied from the kiln crown to the kiln, further calcinated at 900~1200 ℃ and then lead to the finished product after cooling. In the calcination process, carbon dioxide is produced as by-product. Its reaction equation is:
CaCO3 [△]→CaO + CO2 .
Usage limitation
GB 14880-94 (in terms of Ca, g/kg): beverages, cereals and their products, 1.6~3.2; infant food, 3.0~6.0.
GB 2760-2001: Preparation of water 100mg/L (36mg/L in terms of Ca).
Hazards & Safety Information
Category Corrosive items
Toxic classification poisoning
Acute toxicity Intraperitoneal-mouse LD50: 3059 mg/kg
Explosive and hazardous properties it is corrosive to the skin; powdered calcium oxide can be mixed with water to be explode; its mixture with alcohol can be flammable and explosive upon heating
Flammable hazardous characteristics exothermic upon water with its heat being able to cause organic combustion; one of the air pollutants with heating together with alcohol mixture being able to cause combustion
Storage and transportation characteristics Treasury: Ventilated, low temperature and drying; Store separately from combustible materials, acids and phosphorus pentoxide.
Fire extinguishing agent mist water, sand
Occupational Standard TLV-TWA 2 mg/m3; STEL 5 mg/m3
Description
Calcium oxide (CaO, CAS Reg. No. 1305-78-8) is also known as lime, quick lime, burnt lime, or calx. Lime does not occur naturally since it reacts so readily with water (to form hydrated lime) and carbon dioxide (to form limestone). It is produced from calcium carbonate, limestone, or oyster shells by calcination at temperatures of 1,700-2,450℃.
Calcium Oxide is a solid with a very high affinity for water - it will react with water in the air, or in your skin or anywhere it can and form calcium hydroxide. This reaction is exothermic so it releases a lot of heat while it is reacting - there fore as well as being corrosive and causing significant skin irritation, calcium oxide's reaction with water can also cause burns. Calcium hydroxide is basically hydrated calcium oxide. It is alkali so can be corrosive. In solution it makes limewater.
CaO is not found pure in nature but rather is contained in various abundant minerals (i.e. calcite, aragonite, limestone, marble) but vary greatly in their purity (impurities usually include magnesia, iron, alumina, silica, sulfur). Of these iron and sulfur are most troublesome (i.e. where clarity is important in glass). Lime minerals vary in the degree of crystallization and cohesion of the crystalline mass and the homogeneity of the matrix.
Calcium oxide is the principle flux in medium and high temperature glazes, beginning its action (within the glaze) around 1100C. It must be used with care in high-fire bodies because its active fluxing action can produce a body that is too volatile (melting if slightly overfired).
Lime, or calcium oxide, is a principle ingredient in the production of Portland cement, the basis for most mortars and concrete. Hydrated or ‘slaked’ lime is the chemical calcium hydroxide. This chemical is also used in mortars. Both types of lime are strong bases and are also used in food production (calcium hydroxide is commonly used in making corn tortillas), petroleum refining and sewage treatment. In the household it is used by aquarium hobbyists to add bioavailable calcium to fish tanks. It is also found in hair relaxers.
Chemical Properties
Calcium oxide, CaO, occurs as white or
grayish-white lumps or granular powder. The presence of iron
gives it a yellowish or brownish tint.
Physical properties
Calcium oxide is a white caustic crystalline alkali substance that goes by the common name lime. The term lime is used both generically for several calcium compounds and with adjectives to qualify different forms of lime. This entry equates lime, also called quicklime or burnt lime, with the compound calcium oxide. Hydrated lime, made by combining lime with water, is calcium hydroxide and is often referred to as slaked lime (Ca(OH)
2). Dolomite limes contain magnesium as well as calcium. Limestone is the compound calcium carbonate. The term lime comes from the Old English word lm for a sticky substance and denotes lime’s traditional use to produce mortar. Calx was the Latin word for lime and was used to name the element calcium.
History
Calcium oxide dates from prehistoric times. It is produced by heating limestone to drive off carbon dioxide in a process called calcination: CaCO
3(s) CaO
(s) + CO
2(g). At temperatures of several hundred degrees Celsius, the reaction is reversible and calcium oxide will react with atmospheric carbon dioxide to produce calcium carbonate. Efficient calcium oxide production is favored at temperatures in excess of 1,000°C. In prehistoric times limestone was heated in open fires to produce lime. Over time, lined pits and kilns were used to produce lime. Brick lime kilns were extensively built starting in the 17th century and the technology to produce lime has remained relatively constant since then.
Uses
The major uses of lime are metallurgy, flue gas desulfurization, construction, mining, papermaking, and water treatment. About one third of calcium oxide production in the United States is used for metallurgical processes, principally in the iron and steel industry. Calcium oxide is used to remove impurities during the refining of iron ore. Calcium oxide combines with compounds such as silicates, phosphates, and sulfates contained in iron ores to form slag. Lime is also used for purification in other metal refining and to control pH in mining processes such as leaching and precipitation. The calcium oxide is also used in remediation of mine wastes to recover cyanides and to neutralize acid mine drainage.
Uses
Calcium Oxide is a general food additive consisting of white granules
or powder of poor water solubility. it is obtained by heating limestone
(calcium carbonate) in a furnace. it is also termed lime or quicklime.
it is used as an anticaking agent, firming agent, and nutritive supple-
ment in applications such as grain products and soft candy.
Uses
In bricks, plaster, mortar, stucco and other building and construction materials; manufacture of steel, aluminum, magnesium, and flotation of non-ferrous ores; manufacture of glass, paper, Na2CO3 (Solvay process), Ca salts and many other industrial chemicals; dehairing hides; clarification of cane and beet sugar juices; in fungicides, insecticides, drilling fluids, lubricants; water and sewage treatment; in laboratory to absorb CO2 (the combination with NaOH is known as soda-lime, q.v.).
Production Methods
Calcium oxide is commercially obtained from limestone. The carbonate is roasted in a shaft or rotary kiln at temperatures below 1,200°C until all CO
2 is driven off. The compound is obtained as either technical, refractory or agri cultural grade product. The commercial product usually contains 90 to 95% free CaO. The impurities are mostly calcium carbonate, magnesium carbon ate, magnesium oxide, iron oxide and aluminum oxide.
Definition
ChEBI: Calcium oxide is a member of the class of calcium oxides of calcium and oxygen in a 1:1 ratio. It has a role as a fertilizer.
Aroma threshold values
Aroma at 1.0%: intense, high impacting fresh sweet juicy lime, citral with a distilled lime note, cool and
refreshing with green juicy nuances.
Taste threshold values
Taste characteristics at 10 ppm in 5% sugar and 0.1% CA; intense fresh tangy lime juice, citrus citral candy
lime character with notes of West Indian lime
General Description
Calcium oxide appears as an odorless, white or gray-white solid in the form of hard lumps. A strong irritant to skin, eyes and mucous membranes. Used in insecticides and fertilizers.
Air & Water Reactions
Crumbles on exposure to moist air. Reacts with water to form corrosive calcium hydroxide, with evolution of much heat. Temperatures as high as 800° C have been reached with addition of water (moisture in air or soil). The heat of this reaction has caused ignition of neighboring quantities of sulfur, gunpowder, wood, and straw [Mellor 3: 673 1946-47].
Reactivity Profile
A base and an oxidizing agent. Neutralizes acids with generation of heat. Nonflammable, but will support combustion by liberation of oxygen, especially in the presence of organic materials. Reacts very violently with liquid hydrofluoric acid [Mellor 2, Supp. 1:129 1956]. Reacts extremely violently with phosphorus pentaoxide when reaction is initiated by local heating [Mellor 8 Supp.3:406 1971].
Hazard
Evolves heat on exposure to water. Danger-
ous near organic materials. Upper respiratory tract
irritant.
Health Hazard
Causes burns on mucous membrane and skin. Inhalation of dust causes sneezing.
Fire Hazard
Non-combustible, substance itself does not burn but may decompose upon heating to produce corrosive and/or toxic fumes. Vapors may accumulate in confined areas (basement, tanks, hopper/tank cars etc.). Substance will react with water (some violently), releasing corrosive and/or toxic gases and runoff. Contact with metals may evolve flammable hydrogen gas. Containers may explode when heated or if contaminated with water.
Flammability and Explosibility
Not classified
reaction suitability
reagent type: catalyst
core: calcium
Agricultural Uses
Calcium oxide (CaO) is a white powder with a
neutralizing value or calcium carbonate equivalent
(CCE) of 179%, compared to 100% for calcium
carbonate (CaCO
3). For quick results, either calcium
oxide or calcium hydroxide [Ca(OH)
2] is used. Calcium
oxide is also known as lime, unslaked lime, burned lime
or quicklime. Roasting CaCO
3 in a furnace makes
calcium oxide. A complete mixing of calcium oxide with
soil is difficult because it cakes due to absorption of
water.
Industrial uses
Lime is the most widely used reagent in the mineral industry for flotation of sulfides and, in some cases, non-sulfide minerals. The word “lime” is a general term used to describe any kind of calcareous material or finely divided form of limestone and dolomite. In more strict chemical terms, lime is calcinated limestone known as calcium oxide (CaO), quicklime or unslaked lime.The slaked or hydrated lime Ca(OH)2 is the form of lime primarily used in mineral flotation. Production of high-calcium lime is based on calcination of limestone at a temperature of 1100–1300 °C in kilns.
CaCO3+heat--->CaO+CO2 For high-magnesium (dolomitic) limestone, the calcination reaction (at 1000–1200 °C) is CaCO3·MgCO3 (limestone) + heat--->CaOMgO (quicklime-2CO2)
Safety Profile
A caustic and irritating
material. See also CALCIUM
COMPOUNDS. A common air
contaminant. A powerful caustic to living
tissue. The powdered oxide may react
explosively with water. Mixtures with
ethanol may igmte if heated and thus can
cause an air-vapor explosion. Violent
reaction with (I3203 + CaCl2) interhalogens
(e.g., BF3, CIF3), F2, HF, P2O5 + heat, water.
Incandescent reaction with liquid HF.
Incompatible with phosphoms(V) oxide.
Potential Exposure
Calcium oxide is used as a refractory
material; a binding agent in bricks; plaster, mortar, stucco,
and other building materials. A dehydrating agent, a flux in
steel manufacturing, and a labora
First aid
If this chemical gets into the eyes, remove anycontact lenses at once and irrigate immediately for at least15 min, occasionally lifting upper and lower lids. Seek medical attention immediately. If this chemical contacts the skin,remove contaminated clothing and wash immediately withsoap and water. Seek medical attention immediately. If thischemical has been inhaled, remove from exposure, begin rescue breathing (using universal precautions, including resuscitation mask) if breathing has stopped and CPR if heart actionhas stopped. Transfer promptly to a medical facility. Whenthis chemical has been swallowed, get medical attention. Ifvictim is conscious, administer water or milk. Do not inducevomiting. Medical observation is recommended for 24-48 hafter breathing overexposure, as pulmonary edema may bedelayed. As first aid for pulmonary edema, a doctor or authorized paramedic may consider administering a corticosteroidspray.
storage
Color Code—Green: General storage may be used.Prior to working with calcium oxide you should be trainedon its proper handling and storage. Should be stored on dryflooring in a fire-resistant room, well protected from theweather. The area should be cool and adequately ventilated.Store in containers protected from physical damage, acidsand oxidizing materials, such as permanganate, dichromate,or chlorine.
Shipping
UN1910 Calcium oxide, Hazard class: 8; Labels:
8-Corrosive material.
Incompatibilities
The water solution is a medium strong
base. Reacts with water, forming calcium hydroxide and
sufficient heat to ignite nearby combustible materials.
Reacts violently with acids, halogens, metals.
Waste Disposal
Pretreatment involves neutralization with hydrochloric acid to yield calcium chloride.
The calcium chloride formed is treated with soda ash to
yield the insoluble calcium carbonate. The remaining brine
solution may be discharged into sewers and waterways
