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CAS NUMBER: 7778-18-9
EC NUMBER: 231-900-3
MOLECULAR FORMULA: CaSO4
MOLECULAR WEIGHT: 136.14
Calcium sulphate is obtained by firing the Calcium sulphate that has been powdered by firing at 160 ° C.
Calcium sulphate, when wetted and dried, hardens and freezes rapidly and turns into a white-colored fine powder.
Calcium sulphate is obtained by grinding Calcium Sulphate Dihydrate, called Calcium sulphate, and discharging 76% of its water at 192 ° C.
Calcium sulphate (or calcium sulphate) is the inorganic compound with the formula CaSO4 and related hydrates.
In the form of γ-anhydrite (the anhydrous form), Calcium sulphate is used as a desiccant.
One particular Calcium sulphate is better known as plaster of Paris, and another occurs naturally as the mineral Calcium sulphate.
Calcium sulphate has many uses in industry.
All forms are white solids that are poorly soluble in water.
Calcium sulphate causes permanent hardness in water.
The main use of calcium sulphate is to produce plaster of Paris and stucco.
These applications exploit the fact that calcium sulphate which has been powdered and calcined forms a moldable paste upon hydration and hardens as crystalline calcium sulphate dihydrate.
Calcium sulphate is also convenient that calcium sulphate is poorly soluble in water and does not readily dissolve in contact with water after its solidification.
Calcium sulphate converts to the partially dehydrated mineral called bassanite or plaster of Paris.
Calcium sulphate has the formula CaSO4·(nH2O), where 0.5 ≤ n ≤ 0.8.
Temperatures between 100 and 150 °C (212–302 °F) are required to drive off the water within its structure.
The details of the temperature and time depend on ambient humidity.
Temperatures as high as 170 °C (338 °F) are used in industrial calcination, but at these temperatures γ-anhydrite begins to form.
The heat energy delivered to the Calcium sulphate at this time (the heat of hydration) tends to go into driving off water (as water vapor) rather than increasing the temperature of the mineral, which rises slowly until the water is gone, then increases more rapidly.
The endothermic property of this reaction is relevant to the performance of drywall, conferring fire resistance to residential and other structures.
In a fire, the structure behind a sheet of drywall will remain relatively cool as water is lost from the Calcium sulphate, thus preventing (or substantially retarding) damage to the framing (through combustion of wood members or loss of strength of steel at high temperatures) and consequent structural collapse.
Calcium sulphate is exothermic and is responsible for the ease with which Calcium sulphate can be cast into various shapes including sheets (for drywall), sticks (for blackboard chalk), and molds (to immobilize broken bones, or for metal casting).
Mixed with polymers, Calcium sulphate has been used as a bone repair cement.
Small amounts of calcined Calcium sulphate are added to earth to create strong structures directly from cast earth, an alternative to adobe (which loses its strength when wet).
The conditions of dehydration can be changed to adjust the porosity of the hemihydrate, resulting in the so-called α- and β-hemihydrates (which are more or less chemically identical).
On heating to 180 °C (356 °F), the nearly water-free form, Calcium sulphate is produced.
Calcium sulphate reacts slowly with water to return to the dihydrate state, a property exploited in some commercial desiccants.
On heating above 250 °C, the completely anhydrous form called β-anhydrite or "natural" anhydrite is formed. Natural anhydrite does not react with water, even over geological timescales, unless very finely ground.
The variable composition of the hemihydrate and Calcium sulphate, and their easy inter-conversion, is due to their nearly identical crystal structures containing "channels" that can accommodate variable amounts of water, or other small molecules such as methanol.
Calcium sulphate hydrates are used as a coagulant in products such as tofu.
Calcium sulphate is known in the E number series as E516, and the UN's FAO knows it as a firming agent, a flour treatment agent, a sequestrant, and a leavening agent.
Calcium sulphate has a long history of use in dentistry.
Calcium sulphate has been used in bone regeneration as a graft material and graft binder/extender and as a barrier in guided tissue regeneration.
Calcium sulphate is an unusually biocompatible material and is completely resorbed following implantation.
Calcium sulphate does not evoke a significant host response and creates a calcium-rich milieu in the area of implantation.
When sold at the anhydrous state as a desiccant with a color-indicating agent under the name Drierite, it appears blue (anhydrous) or pink (hydrated) due to impregnation with cobalt(II) chloride, which functions as a moisture indicator.
Up to the 1970s, commercial quantities of sulfuric acid were produced in Whitehaven (Cumbria, UK) from anhydrous calcium sulphate.
Upon being mixed with shale or marl, and roasted, the sulphate liberates sulfur trioxide gas, a precursor in sulfuric acid production, the reaction also produces calcium silicate, a mineral phase essential in cement clinker production.
The dissolution of the different crystalline phases of calcium sulphate in water is exothermic and releases heat (decrease in Enthalpy: ΔH < 0).
As an immediate consequence, to proceed, the dissolution reaction needs to evacuate this heat that can be considered as a product of reaction.
If the system is cooled, the dissolution equilibrium will evolve towards the right according to the Le Chatelier principle and calcium sulphate will dissolve more easily.
Thus the solubility of calcium sulphate increases as the temperature decreases and vice versa.
If the temperature of the system is raised, the reaction heat cannot dissipate and the equilibrium will regress towards the left according to Le Chatelier principle.
The solubility of calcium sulphate decreases as temperature increases.
This counter-intuitive solubility behaviour is called retrograde solubility.
Calcium sulphate is less common than for most of the salts whose dissolution reaction is endothermic (i.e., the reaction consumes heat: increase in Enthalpy: ΔH > 0) and whose solubility increases with temperature.
Another calcium compound, calcium hydroxide (Ca(OH)2, portlandite) also exhibits a retrograde solubility for the same thermodynamic reason: because its dissolution reaction is also exothermic and releases heat.
So, to dissolve the maximum amount of calcium sulphate or calcium hydroxide in water, Calcium sulphate is necessary to cool the solution down close to its freezing point instead of increasing its temperature.
Calcium sulphate containing crystal water is called Calcium sulphate (Calcium sulphate).
Calcium sulphate is widely used in jewelry making and dentistry.
When Calcium sulphate is heated at 128 °C, Calcium sulphate loses 75% of the water it contains and turns into Calcium sulphate.
If plaster is mixed with water, Calcium sulphate hardens by binding the water to itself.
Because of this feature, Calcium sulphate is used in plaster molding, decoration works and medicine.
When Calcium sulphate is heated at higher temperatures (163 °C), it loses all of its water and turns into calcium sulphate.
Calcium sulphate is called anhydride.
Calcium sulphate is used as a desiccant in the laboratory and as a filler in the paper industry.
Calcium sulphate appears as odorless, white powder or colorless, crystalline solid.
Crystals sometimes have a blue, gray or reddish tinge or can be brick red.
Density: 2.96 g cm-3.
Calcium sulphate, usually as Calcium sulphate, is universally added to ground cement to control the otherwise rapid ‘flash set’.
Many other compounds have a retarding effect and these have been put on a systematic basis by Forsen, according to their effect on the solubility of alumina.
Following his categorization, retarders may be divided into four sets depending on their actions as a function of concentration.
Typical examples from each group as (i) CaSO4∙2H2O, (ii) CaCl2, (iii) Na2CO3, (iv) Na3PO4.
Type (iv) retarders may hold up setting and hardening indefinitely if used in sufficient quantity, but they are not all harmful and some, such as the calcium lignosulphonates, are used as water-reducing agents.
Calcium sulphate (CaSO4) is one of several sulphate scales and is also called Calcium sulphate.
Calcium sulphate can form either as a result of mixing dissimilar waters or naturally as a result of changes in temperature and pressure as the water travels from the subsurface to the surface treating facility.
CaSO4 solubility is at Calcium sulphates maximum level of 2150 mg/l at approximately 100 °F (38 °C) and diminishes to 2000 mg/l as it cools to 60 °F (15 °C).
The solubility of CaSO4 also declines with increasing temperature above 100 °F with its solubility reducing to 1600 mg/l at 200 °F (93 °C).
Calcium sulphate also increases in solubility as the salinity of the produced water increases.
Calcium sulphate doped with dysprosium was one of the earliest materials to be suggested for use as an OSL dosimeter.
The method chosen, however, was DOSL due to the optically stimulated transfer of charge to shallow metastable traps.
The irradiated sample was optically stimulated with light from a mercury lamp and the luminescence emission was measured after a delay of 15 s from the end of the stimulation.
This relatively long delay was possible because of the long-lived phosphorescence signal, which decayed to 50% of its initial value after about 80 s.
A minimum detectable limit of about 0.01 Gy (± 3%) was measured by these authors.
Calcium sulphate is a naturally occurring calcium salt.
Calcium sulphate is commonly known in its dihydrate form, CaSO4∙2H2O, a white or colourless powder called Calcium sulphate.
As uncalcined Calcium sulphate, the sulphate is employed as a soil conditioner.
Calcium sulphate is a food additive used as an anticaking agent, dough conditioner and strengthener, flour treatment agent, pH regulator, thickenner and yeast food.
Calcium sulphate is a white or white-yellow fine odorless powder.
Calcium sulphate Dihydrate is generally immediately available in most volumes.
High purity, submicron and nanopowder forms may be considered.
Calcium sulphates are salts or esters of sulfuric acid formed by replacing one or both of the hydrogens with a metal.
Most metal sulphate compounds are readily soluble in water for uses such as water treatment, unlike fluorides and oxides which tend to be insoluble.
Organometallic forms are soluble in organic solutions and sometimes in both aqueous and organic solutions.
The physical properties of the three forms of calcium sulphate differ somewhat from each other, but their chemical properties are essentially the same.
Calcium sulphate and calcium hemihydrate are fine white odorless powders or crystalline solids, while the dihydrate may occur either as a powder or as white lumps.
Calcium sulphate is essentially insoluble in water.
As their names suggest, the soluble form of the compound (soluble anhydrite) is somewhat more soluble in water than is the insoluble form (insoluble anhydrite).
The dihydrate and hemihydrate are only slightly soluble in water.
When water is added to the hemihydrate, a reaction occurs that results in the formation of a hard, solid mass (plaster of Paris) used in making casts, such as those used to hold broken bones in place.
Neither the anhydrous form of calcium sulphate or the dihydrate reacts with water in this way.
Both the anhydrous and dihydrate forms of calcium sulphate occur naturally in the form of the minerals anhydrite, angelite, muriacite, and karstenite (CaSO4); and Calcium sulphate (CaSO4·2H2O).
These minerals have been known to humans and used by them for thousands of years.
The most widely used form of calcium sulphate is the dihydrate, Calcium sulphate, which is an important raw material in the construction industry.
Calcium sulphate is used in the manufacture of Portland cement, in specialized plasters (known as Calcium sulphate plasters) for walls, in the production of wallboard, and in cement blocks and mortars.
Calcium sulphate is also used extensively in agriculture as a conditioning agent that adds both calcium ions (Ca2+) and sulphate ions (SO42-) to the soil.
Calcium sulphate is also used as a raw material in the synthesis of other calcium compounds and in the production of plaster of Paris.
The anhydrous form of calcium sulphate also has a number of practical applications, the most important of which are in the manufacture of cement and as a filler in the production of paper.
A filler adds body to paper, making it firmer, brighter, and easier to write, draw, and print on.
Calcium sulphate is used as a desiccant, which is a material that removes water from other substances.
Anhydrous: insoluble anhydrite is used in cement formulations and as a paper filler.
Soluble anhydride, because of Calcium sulphates strong tendency to absorb moisture, is useful as a drying agent for solids, organic liquids and gases; the desiccant used in laboratory and industry is known under the name Drierite.
Calcium sulphate can be regenerated repeatedly and reused without noticeable decrease in its desiccating efficiency.
Calcium sulphate is used for wall plasters; wallboard; tiles and blocks for the building industry; moldings; statuary; in the paper industry.
Calcium sulphate is used in the manufacture of portland cement; in soil treatment to neutralize alkali carbonates and to prevent loss of volatile and dissolved nitrogenous compounds by volatilization and leaching; for the manufacture of plaster of Paris, artificial marble; as a white pigment, filler or glaze in paints, enamels, pharmaceuticals, paper, insecticide dusts, yeast manufacture, water treatment, polishing powders; in the manufacture of sulfuric acid, CaC2,(NH4)2SO4, porous polymers.
USES:
Calcium sulphate (CaSO4) is a white solid that occurs naturally as a mineral anhydrite.
Calcium sulphate is found more commonly as dihydrate, called Calcium sulphate (CaSO4·2H2O).
When heated, Calcium sulphate loses water at 128°C to give a hemihydrate (2CaSO4·H2O), also known as plaster of Paris.
Calcium sulphate is sparingly soluble in water and makes water permanently hard.
Calcium sulphate is used in the manufacture of certain paints, ceramics and paper.
Calcium sulphates naturally occurring form is used in sulphuric acid manufacture.
Calcium sulphate is the cheapest and the most useful material in reclamation of sodic soils.Calcium, solubilized from Calcium sulphate, replaces sodium, leaving behind the watersoluble sodium sulphate, which is leached out as a result of the following reactions in the soil:
Since both reactions are reversible, adequate leaching arrangements have to be made to remove sodium sulphate.
The application of about 40 t/ha of Calcium sulphate in Nevada (USA) was seen to increase water infiltration and the depth of water penetration substantially.
These two measures increased hay yield up to 2.3 t/ha per year.
Calcium sulphate requirement (GR) is the amount of Calcium sulphate necessary to be added to reclaim soil and is calculated using the formula:
Calcium sulphate requirement is equivalent to (Nax)×4.50 metric tons of Calcium sulphate per hectare for a 30 cm fixed depth, where Na, is the milliequivalent of exchangeable sodium to be replaced by calcium from the added Calcium sulphate.
APPLICATION:
-As a flour bleaching agent: Calcium sulphate is mixed with benzoyl peroxide at a ratio of no more than 6:1 by weight.
-As a nutritional supplement: for calcium enrichment 0.64% of calcium sulphate and 0.6% of an emulsifier by flour weight can be added for optimum enrichment.
-As a sodium sulphate substitute: Calcium sulphate can replace up to 32% of sodium in the manufacturer of brown bread without affecting palatability and overall product quality.
-As a pH regulator: Calcium sulphate can be used at a usage level of 0.1 – 0.6%.
FUNCTION:
-Anticaking agent: prevents powder caking, lumping or agglomeration.
-Coloring adjunct: aids in the preservation of color in coatings.
-Dough strengthener: modifies starch and gluten to provide a more stable dough.
-Firming agent: prevents the collapse during processing.
-Flour bleaching treatment
-Leavening aid: provides food for yeast improving leavening.
-Nutrient supplement: provides calcium for nutritional value.
-Stabilizer and thickener: provides body and improved consistency.
-Texturizer: improves baked good texture.
-pH regulator: works as a pH buffer and processing aid
SPECIFICATION:
-Appearance: White Powder
-Melting Point: 128°C
-Boiling Point: 163°C
-Density: 2.32 g/cm3
-Exact Mass: 171.93545
-Monoisotopic Mass: 171.93545
PRODUCTION:
The main sources of calcium sulphate are naturally occurring Calcium sulphate and anhydrite, which occur at many locations worldwide as evaporites.
These may be extracted by open-cast quarrying or by deep mining.
World production of natural Calcium sulphate is around 127 million tonnes per annum.
In addition to natural sources, calcium sulphate is produced as a by-product in a number of processes:
-In flue-gas desulfurization, exhaust gases from fossil-fuel power stations and other processes (e.g. cement manufacture) are scrubbed to reduce their sulfur oxide content, by injecting finely ground limestone or lime.
-This produces an impure calcium sulfite, which oxidizes on storage to calcium sulphate.
-In the production of phosphoric acid from phosphate rock, calcium phosphate is treated with sulfuric acid and calcium sulphate precipitates.
-In the production of hydrogen fluoride, calcium fluoride is treated with sulfuric acid, precipitating calcium sulphate.
-In the refining of zinc, solutions of zinc sulphate are treated with hydrated lime to co-precipitate heavy metals such as barium.
Calcium sulphate can also be recovered and re-used from scrap drywall at construction sites.
These precipitation processes tend to concentrate radioactive elements in the calcium sulphate product.
This issue is particular with the phosphate by-product, since phosphate ores naturally contain uranium and its decay products such as radium-226, lead-210 and polonium-210.
Calcium sulphate is also a common component of fouling deposits in industrial heat exchangers, because its solubility decreases with increasing temperature.
SYNONYM:
Drierite
calcium sulphate
Anhydrous Calcium sulphate
Sulfuric acid, calcium salt (1:1)
Calcium sulphate, anhydrous
calcium;sulphate
Calcium sulphate anhydrous
CaSO4
UNII-E934B3V59H
Calcium sulphate
Calcium sulphate, 99%
Drierite, regular 8 mesh
MFCD00010912
Karstenite
CHEBI:31346
E934B3V59H
Calcium sulphate, Anhydrous, Puratronic
Calcium sulphate
Muriacite
Osteoset
Natural anhydrite
Calcium sulfuricum
Anhydrous sulphate of lime
Oparex 10
Basic calcium sulphate
