General Description
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.
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].
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].
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.
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
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.
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
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 l?m 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: CaCO3(s) CaO(s) + CO2(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.
Definition
ChEBI: A member of the class of calcium oxides of calcium and oxygen in a 1:1 ratio.
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 CO2 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.
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
Flammability and Explosibility
Notclassified
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 (CaCO3). 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 CaCO3 in a furnace makes
calcium oxide. A complete mixing of calcium oxide with
soil is difficult because it cakes due to absorption of
water.
Agricultural Uses
Lime is a white caustic alkaline substance. It consists of
calcium oxide which is obtained by heating limestone,
and has a high neutralizing value.
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)
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.
