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Calcium Compounds
   Calcium carbonate
   Calcium chloride
   Calcium hypochlorite
   Calcium oxide
   Hydroxylapatite
   Lime sulfur
Calcium carbonate CaCO3
: Irritant :
The main use of calcium carbonate is in the construction industry, either as a building material in its own right (e.g. marble) or limestone aggregate for roadbuilding or as an ingredient of cement or as the starting material for the preparation of builder's lime by burning in a kiln.
Calcium carbonate is widely used as an extender in paints, in particular matte emulsion paint where typically 30% by weight of the paint is either chalk or marble.
Calcium carbonate is also widely used as a filler in plastics. Some typical examples include around 15 to 20% loading of chalk in uPVC drain pipe, 5 to 15% loading of stearate coated chalk or marble in uPVC window profile. Fine ground calcium carbonate is an essential ingredient in the microporous film used in babies nappies and some building films as the pores are nucleated around the calcium carbonate particles during the manufacture of the film by biaxial stretching.
Calcium carbonate is widely used medicinally as an inexpensive dietary calcium supplement(1), antacid, and/or phosphate binder. It is also used in the pharmaceutical industry as a base material for tablets of other pharmaceuticals.
As a food additive, it is used in some soy milk products as a source of dietary calcium.
Calcium chloride CaCl2
: Irritant :
Because it is strongly hygroscopic, it can be used to dry air as well as other gases and organic liquids. In this capacity, it is known as a drying agent or desiccant.
Aided by the intense heat evolved during its dissolution, calcium chloride is also used as an ice-melting compound. Unlike the more-common sodium chloride (rock salt or halite), it is relatively harmless to plants and soil. It is also more effective at lower temperatures than sodium chloride.
Calcium chloride tastes extremely salty and is used an ingredient in some foods, especially pickles, to give a salty taste while not increasing the food's sodium content.
Calcium hypochlorite Ca(ClO)2
Used for the disinfection of drinking water or swimming pool water. For use in outdoor swimming pools, calcium hypochlorite can be used as a sanitiser in combination with a cyanuric acid stabiliser. The stabiliser will reduce the loss of chlorine because of UV radiation.
Calcium hypochlorite (known as 'bleaching powder') is also used for bleaching cotton and linen and used in the manufacture of chloroform.
Calcium oxide CaO
Used in water and sewage treatment to reduce acidity, to soften, as a flocculant, and to remove phosphates and other impurities; in paper making to dissolve lignin, as a coagulant, and in bleaching; in agriculture to improve acidic soils; and in pollution control - in gas scrubbers to desulfurize waste gases and to treat many liquid effluents. It has traditionally been used in the burial of bodies in open graves, to hide the smell of decomposition.
Hydroxylapatite Ca5(PO4)3(OH)
Hydroxylapatite makes up 70% of bone, carbonated-calcium deficient hydroxylapatite is the main mineral of which dental enamel and dentin are comprised.
Lime sulfur 
Lime sulfur is sold as a spray for deciduous trees to control fungi, bacteria and insects living or dormant on the surface of the bark. Lime sulfur burns leaves so it is not as useful for evergreen plants.
Bonsai enthusiasts use undiluted lime sulfur to bleach and sterilise portions of trees to give an aged look known as Jin.