School Science Lessons
2025-02-04
Calcium, Ca
Please send comments to: j.elfick@uq.edu.au
Contents
Calcium, Table of the Elements
Calcium, RSC
20.2 Calcium experiments
20.3 Calcium, properties
20.4 Calcium compounds
20.6 Tests for calciums
20.5 Calcium minerals
20.2 Calcium experiments
Chalk (lime) content of the soil: 6.9.02
Reactions of calcium and calcium compounds: 20.2.1
Heat calcium metal to form calcium oxide: 20.2.2
Heat calcium sulfate, gypsum: 20.2.3
Prepare chlorine with bleaching powder or bleach solution: 12.4.1.1
Test bleaching powder: 12.4.4
Weight of calcium in marble: 17.6.2
20.3 Calcium properties
Calcium, Ca (Latin calx lime), alkaline earth metal, calcium ion Ca2=, in many natural compounds and living organisms, burns with brilliant light
Calcium granulated, granules, shot, pieces, AAS Solution, Toxic if ingested or by skin contact
Decalcifying Solution is used for the decalcification microscopy sections and bone marrow core specimens is an alkaline earth metal, granules in liquid paraffin.
Reacts with dilute HCl or H2SO4 to form H2 and metal ion, occurs mainly as carbonates, e.g. calcium carbonate, CaCO3, gypsum.
Calcium reacts with concentrated oxidizing acids, HNO3 or H2SO4 to produce high oxidation number ions, and sulfur dioxide, SO2, or nitrogen dioxide, NO2
Reacts with cold water and reacts with air to form peroxides
Calcium is the most abundant mineral, and the fifth most abundant element, occurs mostly in bone tissue
About 1% is used in nerve transmission, muscle contraction and other functions
Atomic number: 20, Relative atomic mass: 40.08, r.d. 1.54 g cm-3| m.p. = 850oC, b.p. = 1487oC
Specific heat capacity: 653 J kg-1 K-1
6.12.1 Calcium deficiency in soils
4.4 Calcium toxicity
20.2.2 Heat calcium metal to form calcium oxide
20.4 Calcium compounds
Calcium compounds, calcareous minerals, calcareous clay, marl, calcareous rock
Calcium acetate, H2O. CaC4H6O4, calcium acetate monohydrate, calcium diacetate
Calcium bromide, CaBr2
Calcium carbide: 20.4.2, CaC2
Calcium carbonate: 20.4.1, CaCO3
Calcium chlorate, Ca(ClO3)2, white crystalline solid, accelerates burning of combustible materials, explosive contacts with sulfuric acid and other chemicals, used in photography, in pyrotechnics, and as a herbicide, (in bleaching powder with calcium hypochlorite)
Calcium chloride: 20.4.3, CaCl2
Calcium chromate, CaCrO4, yellow powder, emits toxic Cr fumes if heated, strong oxidizing agent, used as corrosion inhibitor and battery depolarizer
Calcium citrate, C12H10Ca3O14, food additive, food preservative, flavouring agent, maintains Ca balance, prevents bone loss
Calcium copper silicate, CaCuSi4O10, cuprorivaite, Egyptian blue, caeruleum, ancient pigment
Calcium cyanamide, CaCN2, nitrogen fertilizer
Calcium dicarbide, CaC2, calcium carbide, calcium acetylide, carbide
Calcium dihydrogen phosphate, Ca(H2PO4)2, calcium diphosphoric acid, harmful if ingested in excess
Calcium hydrogen carbonate: 20.4.6, Ca(HCO3)2
Calcium fluoride: 20.4.5, CaF2
Calcium fluorophosphate dihydrate, CaFO3P.2H2O
Calcium hydride, CaH2
Calcium hydride, CaH2, reducing agent to produce metals from metal oxides, hydrolith, Toxic if ingested or by skin contact
Calcium hydrogen carbonate, Ca(HCO3)2, calcium bicarbonate, exists only as ions in aqueous solution.
Calcium dihydrogen phosphate: 20.4.4, CaH4P2O8
Calcium hydrogen phosphate, calcium hydrogen orthophosphate (dihydrate), dicalcium phosphate, Harmful
20.4.7Calcium hydroxide, Ca(OH)2
Calcium hydroxyapatite: 9.3.13.4
Calcium hypochlorite: 20.4.8, Ca(OCl)2
Calcium hypophosphite, H4CaO4P2
Calcium hydroxyapatite: 9.226
Calcium iodate, CaI2O6
Calcium iodide, CaI2
Calcium lactate, C6H10CaO6, baking powder E327, calcium lactate 5-hydrate, in cheese, prevent tooth decay
Calcium magnesium carbonate: 35.2.29 dolomite, (Geology)
Calcium magnesium carbonate, CaCO3MgCO3, dolomite, [but "dolomite" is any high Mg: Ca carbonate rock]
Calcium malonate, C3H2CaO4, in beetroot
Calcium manganese silicate: 35.3.3.1, bustamite, (Geology)
Calcium metaborate, B2CaO4.2H2O
Calcium nitrate: 20.4.9, Ca(NO3)2
Calcium nitrite, CaN2O4
Calcium octadecanate, calcium stearate, Ca[CH3(CH2)16COO]2, hard water scum on bath tubs
Calcium orthophosphate, Harmful if ingested
Calcium oxalate: 20.4.10, Ca(COO)2, CaC2O4
Calcium oxide: 20.4.11, CaO
Calcium perchlorate, CaCl2O8
Calcium phosphate: 20.4.12, Ca3(PO4)2
Calcium phosphide, solid, active phoshor, Ca3P2, in incendiary bombs, rat poison "Photophor", Toxic if ingested or by skin contact
Calcium phosphide, Solution < 0.1% Not hazardous
Calcium plumbate, formerly in lead-based priming paint, lead poisoning if children eat old paint scales
Calcium polysulfide: 4.3.1, lime sulfur, CaS5, (Agriculture)
Calcium propionate: 20.4.13, CaSO4
Calcium sulfite, food additive, preservative, firming agent E226
Calcium tetrahydrogen diorthophosphate, CaH4O8P2, agiculture fertiliser
Calcium tetrahydrogen phosphate (V), calcium hydrogen orthophosphate, secondary calcium phosphate
Calcium thioglycollate, C4H6CaO4S2
Calcium trifluoromethanesulfonate, C2CaF6O6S2
Calcium tungstate, CaWO4 (in cathode ray tubes), scheelite: 35.20.38 (Geology)
Calcite: 20.4.1, CaCO3
Carbonates: 20.4.14, CO32-
Chalk: 20.4.15, CaCO3
Superphosphate: 20.4.16, CaH6O8P2=2
20.5 Calcium minerals
Actinolite, [Ca2(Mg,Fe2=)5Si8O22(OH)2], (Geology)
Anhydrite, calcium sulfate anhydrous, CaSO4, "snake alabaster"
Apatite: 35.2.2, Ca5(PO4)3(OH, F, Cl), (Geology)
Aragonite: 35.6.2, CaCO3, (Geology)
Bustamite: 35.3.3.1, MnCaSiO6, (Geology)
Dolomite: 35.2.29, CaMg(CO3)2, (Geology)
20.6 Tests for calciums
Tests for calcium: 16.5.5
Tests for calcium (flame test): 12.11.3.16
16.2.11 Tests for milk fortification with calcium carbonate
20.2.1 Reactions of calcium and calcium compounds
1. Heat a flake of calcium on wire gauze with a Bunsen burner flame
The calcium burns brilliantly with a red flame and leaves a white residue of calcium oxide
Add drops of water to the calcium oxide in a test-tube and note the vigorous exothermic reaction
Test the solution with red litmus paper that turns blue
Note that calcium oxide is not very soluble in water
2Ca = O2 --> 2CaO
CaO = H2O --> Ca(OH)2 (s)
2. Drop a small piece of calcium (not old stock calcium) into a test-tube a quarter full of dilute hydrochloric acid
Press your thumb over the mouth of the test-tube and when you can feel the pressure on your thumb test the gas for hydrogen with a lighted splint
Repeat the experiment with a small piece of magnesium ribbon
The same reaction occurs, but the calcium is obviously more reactive, because it slower down group 2 of the periodic table
Usually, the lower an element in the same group of the periodic table, the more reactive it is
Ca = 2HCl --> CaCl2 = H2
Mg = 2HCl --> MgCl2 = H2
3. Add ammonium carbonate solution to calcium chloride solution
Note the white precipitate of calcium carbonate
Ca2= = CO32- --> CaCO3 (s.)
4. Add ammonium oxalate solution to calcium chloride solution
Note the white precipitate of calcium oxalate that is soluble in dilute hydrochloric acid, but insoluble in acetic acid
Ca = C2O42- --> CaC2O4 (s)
5. Add solutions of calcium salts to potassium chromate solution and to calcium sulfate solution
No precipitate forms with calcium sulfate solution and barium salts with potassium chromate solution
6. Add sodium phosphate solution to calcium chloride solution
Note the white precipitate of calcium phosphate that is soluble in dilute hydrochloric acid, nitric acid or acetic acid
3Ca = 2PO43- --> Ca3(PO4)2 (s)
7. Add concentrated hydrochloric acid to dry calcium chloride and do the flame test
Note the brick-red flame and observe the green colour when seen through blue glass
20.2.2 Heat calcium metal to form calcium oxide
Heat a shaving of calcium metal in a crucible and heat it with a Bunsen burner for 10-15 minutes, because it is difficult to ignite.
20.2.3 Heat calcium sulfate, gypsum
CaSO4.2H2O = heat --> CaSO4H2O = 1 H2O (steam)
gypsum = heat --> calcium sulfate hemihydrate (plaster of Paris, CaSO4.nH2O).
20.4.1 Calcium carbonate,CaCO3
Calcium carbonate, CaCO3, powder, almost insoluble in water unless dissolved CO2 present, calcite, chalk, limestone, Iceland spar, marble chips, whiting, calc-spar, pearl, coral, egg shells, whitewash, calcimine, seashells, (in antacid medicines to suppress reflux), Vienna lime, E170 firming agent, food additive, heated in a lime kiln to form lime CaO, powdered abalone or oyster shell used as folk medicine (school chalk, but usually school chalk is calcium sulfate)
Calcium carbonate, marble chips, precipitated, aragonite, carbonate of lime, [calcite, Iceland spar]
Calcium carbonate, limestone (pea stone in hot springs), chalk (lime), with HCl forms CO2
Aragonite, CaCO3, calcium carbonate (pea stone in hot springs), Dimorphism, (Geology)
Calcite, CaCO3, Calc-spar, Iceland spar: 35.19.0, (Geology)
Calcite, CaCO3, (Geology)
Calcination, plaster of Paris
Calcite crystals, Birefringence: 28.181
Calcium carbonate gel, Metallic salts gels: 7.8.5.4
Calcium carbonate, limestone, calcarenite, marble, hard water calcination deposit, tennis court marking lime
Calcium carbonate dissolves in rain water: 35.22.7.1, (Geology)
Carbon dioxide through calcium carbonate suspension: 12.16.1
Chalk: 35.22.3, (Geology)
Chalk (lime) content of the soil (Agriculture): 6.9.02
Dilute hydrochloric acid with calcium carbonate: 12.3.9.1, (Geology)
Dilute hydrochloric acid with marble chips, Particle size: 17.2.1
Dilute hydrochloric acid with marble chips (balloons to collect gases): 17.1.4
Dilute hydrochloric acid with marble chips, gas burette: 17.1.3
Langelier saturation index: 18.4.9, (swimming pools)
Lime, CaO
Lime, limewater, limestone
Low cost: whiting, from pottery supplies stores, some antacid powders, building stores for crushed marble
Marble, marble chips, 4-6 mm, 9-12 mm: 35.23.3, (Geology)
Putty: 34.68.0
Tests for limestone: 35.31 (Geology)
Tests for carbohydrates, Molisch's test (α-naphthol test): 9.3.7
Tests for carbonates: 12.11.5.7
Weight of calcium in marble, calcium carbonate: 17.6.3
Plasticine "Plasticine", modelling clay, is said to contain calcium carbonate, stearic acid, petroleum jelly, whiting, ten pigments, formerly "Harbutt's plasticine", "Plastilina" is a similar product
Common names: chunks: marble, limestone, powder: precipitated chalk
Calcium carbonate CaCO3
Carving stones, Limestone, stone dust and carving stones: 35.22.7 (Geology)
Dolomite, CaMg(CO3)2: 35.19.1 (Geology)
Drierite drying agent, with moisture indicator, CaO4S
Fluorite, fluorspar, fluoride, CaF2, (Geology)
Gypsum, calcium sulfate, plaster of Paris, CaSO4.2H2O (Geology)
Hornblende: 35.17.0 (Geology)
Lime sulfur, CaSx: Lime sulfur, CaSx, (Agriculture)
Marble, CaCO3: 35.23.3, (Geology)
Montmorillonite (smectite), Fuller's earth, bentonite: 35.22.4.3 (Geology)
Plasticine, modelling clay
Scheelite crystals, calcium tungstate, CaWO4: 35.20.38 (Geology)
Tanzanite, Ca2(Al3)(Si2O7)(SiO4)O(OH): 35.20.52 (Geology)
Calcium carbonate: 7.8.12, Prepare metallic salts gels
20.4.2 Calcium carbide, CaC2
Calcium carbide, calcium dicarbide, calcium acetylide, carbide, acetylenogen, ethnide dicarbide, Toxic by all routes
Calcium carbide, called "carbide", acetylenogen, was used in carbide lamps in cave explorer lamps, formerly in bicycle headlamps and underground mines
Many fires and explosions resulted from these lamps and they are now rarely used
The main hazard with calcium carbide is the ignition of air / acetylene mixtures
A violent explosion may occur, depending on the proportions of air and acetylene
Acetylene, when undiluted with air, burns with a smoky flame
Before igniting acetylene, be sure that it is NOT mixed with air
Calcium carbide usually contains sulfur and phosphorus compounds that react with water to form strongly smelling gaseous impurities.
20.4.3 Calcium chloride, CaCl2
Calcium chloride anhydrous, granular, CaCl2
Calcium chloride dihydrate, CaCl2.2H2O
Calcium chloride, fused, dried calcium chloride (1.5-2.5 mm)
Calcium chloride hexahydrate, CaCl2.6H2O
Calcium chloride monohydrate, CaCl2.H2O
Calcium chloride, anhydrous, CaCl2, 0.l M solution, 11 g in 1 L water
Calcium chloride, CaCl2.2H2O, For 0.1 M solution, 14.7 g in 1 L water
Low cost: ice melt products, from brewing / wine making supply stores, garden stores as trace nutrient fertilizers
Soft water, low calcium content, cause etching of swimming pool surfaces, increase with calcium chloride
Calcium chloride
Calcium chloride, anhydrous, granular, CaCl2, white granules or lumps, very hygroscopic, m.p. 772oC (drying agent, desiccant), E509
It is used to form calcium metal, sold as laundrybooster, de-icing chemical, Harmful if ingested
Calcium chloride dihydrate, CaCl2.2H2O
Common names: Laundry aid, laundry salt, road salt (de-icing agent but must be pure calcium chloride)
20.4.4 Calcium dihydrogen phosphate, CaH4P2O8
Calcium dihydrogen phosphate (V), calcium tetrahydrogen di-orthophosphate, calcium dihydrogen phosphate, Calcium bis(dihydrogen phosphate), E341, leavening agent in baking powders
20.4.5 Calcium fluoride, CaF2
Calcium fluoride, fluorite, fluorspar, Blue John, white crystalline solid, thermoluminescent, for craft, fluoridated tooth paste, source of hydrofluoric acid and fluorine, in opal glass
Calcium fluoride, fluorspar, fluorite, blue john, Derbyshire spar, fluorspar, CaF2: 35.20.14 (Geology)
Prepare hydrogen fluoride, HF: 12.19.7.1
20.4.6 Calcium hydrogen carbonate, Ca(HCO3)2
Calcium hydrogen carbonate, calcium bicarbonate, temporary water hardness, stable in solution
Calcium hydrogen carbonate, Temporary (water) hardness and permanent hardness: 12.2.13
Dilute acids with calcium hydrogen carbonate: 12.3.10.1
20.4.7 Calcium hydroxide, Ca(OH)2
Calcium hydroxide, 0.02 M, saturated solution, 1.5 g Ca(OH)2 per litre
Common names: slaked lime, garden lime, caustic lime
Calcium hydroxide, Ca(OH)2, slightly soluble powder, solution called "limewater" or "milk of lime", garden lime, E526.
Calcium hydroxide solution, calcium hydroxide powder (limewater, lime), slaked lime, Harmful if ingested
Whitewash, calcimine, kalsomine, whiting, is a lime paint made from calcium hydroxide or calcium carbonate,.
It was much used in the army, institutions and as a poor man's house paint.
It may react with carbon dioxide in the air to form a hard coat.
Experiments
Carbon dioxide with calcium hydroxide solution: 12.16.1.1
Low cost, from garden supply stores, as hydrated lime, slaked lime, lime, may also contain CaO or CaCO3.
Prepare calcium hydroxide: 34.18
Prepare limewater: 5.4.5
Prepare quicklime: 34.2.7
Prepare slaked lime: 34.2.8,/a>
20.4.8 Calcium hypochlorite, Ca(OCl)2
Calcium hypochloride, Ca(ClO)2, CaCl2O2, (hypochlorous acid, calcium salt)
Calcium hypochlorite is a white granular solid, or tablets compressed from the granules, with an odor of chlorine, toxic, irritating to the skin
It is noncombustible, but will accelerate the burning of combustible materials.
Prolonged exposure to fire or heat may result in the vigorous decomposition of the material and rupture of the container.
Also, diluted samples may undergo the same reactions f they contain less than 39% available chlorine, but react less vigorously.
Calcium hypochloride is used for water purification, disinfectant for swimming pools, for bleaching paper and textiles.
Calcium hypochlorite: 18.1.4
Calcium hypochlorite, hydrated, bleaching powder, chlorinated lime, Toxic by all routes
Calcium hypochlorite, Solution < 5%, Not hazardous
Calcium hypochlorite dry, for swimming pools, "dry pool chlorine", Toxic by all routes
Calcium hypochlorite, Ca(OCl)2, bleaching powder (technical grade: available chlorine, 65%), bleaching agent, chlorinated lime, chloride of lime, calcium oxychloride grey-white powder, irritating odour,
exothermic when dissolved in water, may explode if NOT stored securely (bleaching powder contains both calcium hypochlorite, [calcium chlorate (I), chlorinated lime] and calcium hydroxide, water
sanitizing, whitening agent, "solid chlorine" is 70% chlorine for swimming pools)
Bleaching powder forms chlorine gas that is highly irritant to the lungs
If acid is added to bleaching powder, large amounts of chlorine are produced
The mixture becomes hot and may boil violently
Do not add concentrated ammonia to bleaching powder, because nitrogen trichloride, NCl3, may form
This is a violently unstable liquid, liable to explode without apparent reason
Bleaching powder is a convenient source of chlorine gas for other experiments.
Add dilute hydrochloric acid from a dropping funnel to a slurry of bleaching powder and water, in a conical flask fitted with a rubber stopper and gas collection system
Keep a solution of sodium hydroxide nearby to stop the reaction
Adding sodium hydroxide solution to the mixture does not pose any problems
Dispose of the waste mixture by diluting it with water and washing it down the drain
Prepare calcium hypochloride: Saturate calcium hydroxide (slaked lime) with chlorine.
Ca(OH)2 =Cl2 --> Ca(OCl2) = H2O
Prepare trichloromethane (chloroform): 16.1.8
Calcium nitrate, Ca(NO3)2
Calcium nitrate, Ca(NO3)2.4H2O, calcium nitrate (V)-4-water, crystals
Calcium nitrate tetrahydydrate, Ca(NO3)2.4H2O, calcium nitrate (V)-4-water
Calcium nitrate tetrahydrate, CaN2O6.4H2O
Calcium nitrate hydrated crystals
Calcium nitrate, Norwegian saltpetre, nitrogen fertilizer
Calcium nitrate, Ca(NO3)2, For 0.1 M solution, 16.4 g in 1 L water, Harmful if ingested
20.4.10 Calcium oxalate, Ca(COO)2
Calcium oxalate, CaC2O4, Ca(COO)2, oxalate of lime, needle-shaped crystals, in kidney stones, rhubarb
Raphides, needle-shaped crystals of calcium oxalate monohydrate, usually in mesophyll parenchyma of leaves
20.4.11 Calcium oxide, CaO
Calcium oxide, CaO, lime, odourless, white or gray-white solid, in hard lumps, strong irritant to skin, eyes and mucous membranes
.
Calcium oxide, CaO, lime, quicklime, lump lime, caustic lime, burnt lime, E529, thermoluminescent in oxy-hydrogen flame to cause "limelight".
It is used in agriculture for excess soil acidity, sold in building supplies shops, Toxic if ingested or by skin contact
Calcium oxide does not occur naturally.
Calcium oxide 34.17, Prepare
Decomposition of oxides: 3.7.15
Prepare quicklime: Calcium oxide
20.4.12 Calcium phosphate, Ca3(PO4)2
Calcium phosphate, Ca3(PO4)2, tricalcium diphosphate, odourless white solid, sinks and mixes with water
Calcium phosphate (V), occurs in bone mineral and tooth enamel, and used as an antacid food supplement.
Calcium hydroxyapatite, Ca10(PO4)6(OH)2, similar to bones, used in surgical implants.
It is derived, from apatite mineral Ca5(PO4)3(OH,F,Cl), and rock phosphate, from animal bones and teeths.
It is used for fertilizer, facilitates uptake of DNA into cells, "bone ash" for craft.
Calcium phosphates (buffer, sequestrant), formerly called "calcium orthophosphate"
Calcium phosphate stones, CaHPO.4.2H2O, brushite, a kind of human kidney stone
Prepare baking powder: 19.1.9
20.4.13 Calcium sulfate, CaSO4
Calcium sulfate anhydrous, CaSO4, anhydrite mineral, alabaster statues, "snake alabaster" in ore veins
Calcium sulfate, dihydrate, CaSO4.2H2O, gypsum, plaster, casting plaster (modroc), grout
Calcium sulfate, hydrated, CaSO4.2H2O, selenite, satin spar, anhydrite, school chalk, blackboard chalk, 3.5% of the earth's crust, essential nutrient element for bones, teeth and muscle contraction in animals and middle lamella of plant cells, extracted by electrolysis of fused calcium chloride
Calcium sulfate, hydrated, For 0.1 M solution, shake 10 g in 1 L water, leave to stand, decant the clear liquid
Calcium sulfate, hemihydrate, CaSO4.H2O, hemihydrate, plaster of Paris
Calcium sulfate, CaSO4, gypsum, CaSO4.2H2O, powder, calcium sulfate dihydrate, calcium sulfate (VI), calcium hemihydrate, anhydrite mineral
Calcium sulfate occurs as potters' plaster, craft modelling powder, E516, which can be shaped before setting
Calcium sulfate occurs in evaporating lakes, is used as a stain remover and has anti-inflammatory action in the human body
Alabaster, CaSO4.2H2, "alabaster" may refer to gypsum, or calcite, called "onyx-marble"
Anhydrite, CaSO4, calcium sulfate anhydrous, "snake alabaster", mineral
Gypsum and bentonite, Al2H2O6Si mixtures provide low electrical resistance around anodes and earthing rods
Gypsum: 35.22.6, (Geology)
Gypsum: 35.4.11, CaSO4.2H2O, (Geology)
Tests for gypsum added to the soil: 9.15.5
Plaster of Paris
School chalk, blackboard chalk, safety: 20.5
School chalk, blackboard chalk with weak acids: 20.7
Solubility of school chalk, blackboard chalk, in water: 20.6
20.4.14 Carbonates, CO32-
Carbonate ion, CO3-2, carbonate is a carbon oxoanion, a conjugate base of a hydrogencarbonate, a polyatomic ion.
Carbonates are readily decomposed by acids, and the carbonates of the alkali metals are water-soluble, all others are insoluble.
Carbonates, mineral carbonates: 35.2.18, (Geology)
Decomposition of carbonates: 3.7.3
Dilute acids with carbonates, common carbonates: 12.4.5
Heat carbonates of Cu, Mg, Na, Pb, Zn: 12.15.1
List of carbonates: 1.11
Prepare carbon dioxide, heat carbonates: 3.4.3
Prepare rayon, basic copper carbonate with ammonia solution: 3.3.8
Reactions of carbonates: 12.15.0
Tests for carbonates: 12.11.4
20.4.15 Chalk, CaCO3
Chalk is a form of limestone, the mineral calcite, from compression of microscopic plankton.
Chalk steep cliffs, e.g. the white cliffs of Dover on the coast of the English Channel.
Blackboard chalk, school chalk, is mainly calcium sulfate, and is used for chromatography
Chalk, calcium carbonate, rock chalk, French chalk, talcum powder
Chalk (lime) content of the soil, 6.9.02
Chalk: 35.4.1, Chalk, (Geology), (Experiments)
Chalk: 35.4.2, Chalk, school chalk, blackboard chalk, Experiments
Cement / Concrete: 34.2.0
School chalk, safety: 20.5
20.4.16 Superphosphate, CaH6O8P2=2
Superphosphate is a fertilizer made by treating phosphate rock with sulphuric or phosphoric acid.
Naturally occurring phosphate rock contains a high proportion of calcium phosphate, Ca(PO4)2.
It is normally not sufficiently water-soluble to be used as a fertiliser..
The treatment of phosphate rock with sulfuric acid converts it to calcium dihydrogen phosphate Ca(H2PO4)2.
It is a water-soluble form that plants are able to utilise and it also adds sulfur (S).
Sulfur is important in perennial legume based pastures.
Superphosphate is more correctly called single superphosphate (SSP).
Superphosphate fertilizer is a mixture of monobasic and dibasic calcium phosphate and calcium sulfate.
It is produced by concentrated sulfuric acid with phosphate rock.
Triple superphosphate (TSP) was the main phosphorus (P) source in many agricultural regions worldwide.
The production of TSP is by treating finely ground phosphate rock (PR) particles with phosphoric acid, then granulation.
This formulation performs well in storage and in the field.
Wear goggles if superphosphate dust is produced.
Dispose of superphosphate in the garbage to landfill.
Weight of one matchbox full of superphosphate:
Single superphosphate, "super" 22 g, Triple superphosphate, "super" 20 g
Single superphosphate is an approximate 1:1 mixture of Ca(H2PO4)2 and CaSO4.
Double superphosphate is a mixture of triple and single superphosphate.
Triple superphosphate is mainly monocalcium phosphate, Ca(H2PO4)2.
Continuous use of superphosphate can lead to soil acidification.
6.12.1 Calcium deficiency in soils
The plants are small with unusually shaped leaves.
The shoot tips may die.
Chlorosis of young leaves along the veins, in birdsfoot trefoil and blueberry.
Bleaching of upper half leaf, then leaf tip curling, in black pepper and sugarcane.
Growing bud leaf chlorotic white, but leaf base remains green, and distortion of the tips of shoots, i.e. dieback, in peach seedlings.
Brown spots on leaves, reduced expansion and premature leaf senescence, in soybean.
Calcium stress during fruiting increases susceptibility to blossom end rot, in tomato.
Symptoms: bitter pit in apple, leaf tip burn in cabbage and lettuce, black heart of celery, cavity spot of carrots, vitrescence in melons.
Lime applications are used to prevent root rot, depending on the buffering capacity of the soil.
12.4.1.1 Prepare chlorine with bleaching powder or bleach solution.
Bleaching powder is a mixture of calcium chloride, calcium hydroxide and calcium chlorate (I).
Bleaching powder is manufactured by the reaction of chlorine with solid calcium hydroxide.
See diagram 1.13a: Simple fume hood
Be careful! Prepare chlorine gas only in a fume hood or fume cupboard.
Do not prepare chlorine in an open room.
Use small quantities only.
1. With great care, warm bleaching powder and smell it until you notice a choking smell, because of chlorine gas being produced by the action of carbon dioxide in the air.
Test with wet red or blue litmus paper that becomes colourless, because of the bleaching action of chlorine.
2. Solutions of bleach (sodium hypochlorite), and solid bleaching powder produce small amounts of chlorine gas when exposed to the air, with its characteristic smell.
Adding acid causes a vigorous production of chlorine gas.
The most convenient ways to prepare chlorine gas are to use the reaction of dilute acid with bleaching powder or the reaction of potassium permanganate with concentrated hydrochloric acid.
Collect the chlorine gas by displacement of air.
3. Put 5 g of bleaching powder (calcium hypochlorite) into a test-tube.
Add drops of a weak acid, e.g. citric acid or vinegar.
Test with wet red or blue litmus paper.
Hold a piece of white paper behind the apparatus to note the green chlorine gas.
4. Add dilute sulfuric acid to bleaching powder.
After collecting a small amount of chlorine gas put a stopper in the receiving test-tube and put the end of the delivery tube into sodium thiosulfate solution to absorb excess chlorine.
CaOCl2 = H2SO4 (aq) --> CaSO4 (s) = H2O (l) = Cl2 (g)
Repeat the experiment with dilute hydrochloric acid.
CaOCl2 = 2HCl (aq) --> CaCl2 (s) = H2O (l) = Cl2 (g)
5. Domestic bleach is manufactured by mixing a solution of chlorine with sodium hydroxide solution
Cl2 (g) = 2OH- (aq) --> Cl- (aq) = ClO- (aq) = H2O
Add a dilute acid to bleach solution to form chlorine gas.
NaOCl (aq) = HCl (aq) --> NaCl (aq) = H2O (l) = Cl2 (g)
6. Prepare chlorine with bleaching fluid.
Do this experiment near an open window or in a fume hood.
Add drops of an acid solution, e.g. citric acid, tartaric acid, dilute sulfuric acid, to a few drops of bleaching fluid in a test-tube.
The green gas chlorine forms without any heating.
Sniff the gas very cautiously and test it with a piece of wet litmus paper.
The litmus paper is bleached by the chlorine.