School Science Lessons
2024-06-17
Potassiun, K
(topicIndexPotassium) Contents
Potassium
Potassium compounds
Potassium minerals
Prepare potassium compounds
Potassium, Table of the Elements
Potassium, RSC

Platinum, Pt
Pyrogallol
Pyrrolines
Red phosphorus, P4
White phosphorus, P4
Purpureacin
Pyridoxine
Pyrolysis
Perindopril
Phosphorescence
PotassiumsafetyH">Potssium safety
Potassium safety: 12.14.01
Potassium deficiency in soils: 6.12.5
Potassium toxicity: 4.12
Storing sodium and potassium: 3.7.9
Storing sodium chlorate and potassium chlorate: 3.7.10
Tests for potassium: 12.11.3.25, sodium perchlorate
Tests for potassium: 12.11.3.1.1, tetraphenylborate test
Chemicals Not permitted in schools, Australia: Potassium and compounds
Potassium
Potassium, K (Dutch potasch, potasschen potash) (Latin kalium, K), metal, potassium rod stored in mineral oil,
AAS solution, toxic if ingested or contacts skin
Potassium is a soft and shiny white alkali metal, highest metal in the reactivity series so does not occur in the free state.
Potassium is about 2.5% of the earth's crust, is available in the laboratory as pieces of the metal in liquid paraffin and is used widely in chemistry.
Potassium is the " K" in the common fertilizer NPK, usually as (K2O).
It reacts with dilute HCl or H2SO4 to form H2 and metal ion, reacts with concentrated oxidizing acids, HNO3 or H2SO4 to produce high oxidation number ions,
and sulfur dioxide SO2 or nitrogen dioxide, NO2.
Potassium reacts with cold water and reacts with air to form peroxides.
Potassium has less concentration in extra cellular fluids than in intracellular fluids, where it is the primary cation.
Potassium ions are lost in sweat along with sodium ions.
Potassium metal is banned in many school systems.
Potassium reacts violently with water to form hydrogen gas that may ignite or explode.
Destroy potassium safely with 2-methylpropan-2-ol.
Potassium forms a crust of yellow oxide that may explode when cut.
For school science experiments, use sodium or lithium instead of potassium.
Atomic number: 19, Relative atomic mass: 39.0983, RD 0.86, MP = 63.7oC, BP = 774oC
Specific heat capacity: 753 J kg-1 K-1
Potassium compounds
Argol, tartar
Beeswing
Potash
Prepare potassium compounds
Prepare chlorine with hydrochloric acid / potassium manganate (VII): 12.4.1.2
Prepare chrome alum: 12.5.10
Prepare crystal clusters: 3.1.3
Prepare ethanal with potassium dichromate: 16.3.2.7
Prepare ethanal with potassium manganate (VII): 16.3.2.6
Prepare invisible inks: 4.19
Prepare iodic acid, HIO3, and potassium iodate, KIO3: 12.19.6.3.
Prepare oxygen gas with potassium manganate (VII): 3.49.2
Prepare potash from ash: 6.9.16
Prepare potash alum: 12.14.1
Prepare potassium bromide: 12.19.9.5
Prepare potassium dichromate: 12.5.6
Prepare potassium nitrate from manure: 3.9.1
Prepare potassium perchlorate: 12.19.8.5.
Prepare potassium permanganate: 12.8.3
Potassium minerals
Amazonite, microcline, KAlSi3O8, blue-blue/green crystals
Biotite mica, K2(Mg,Fe)6-4(Fe,Al,Ti)0-2(Si6-5Al2-3O20)(OH,F)4, (Geology)
Illite, KAl4(Si, Al)8O20(OH)4, KAl4(Si, Al)8O18.2H2O, most common clay mineral
Langbeinite, K2Mg2(SO4)3, may be in "potash fertilizers"
Alkaline feldspars, Microcline, KAlSi3O8, (Geology)
Moonstone, K(SiAl)4O8, feldspar
Muscovite mica, white mica, K2Al4Si6Al2O20(OH,F)4, (Geology)
Potassium chloride, Sylvite (sylvine) bitter taste, KCl.
Potash
Potash, potassium oxide, K2O
"Potash" was the name given to the potassium hydroxide, potassium carbonate and other potassium salts remaining when wood was burnt completely.
Then the ashes were dissolved in water boiling in iron pots, so "pot-ash".
Potassium carbonate
Potassium hydroxide
The potash could be boiled with fat to make produce soap.
Prepare soap: 12.9.0
Potash was used as a valuable. but cheap, plant fertilizer.
Prepare potash from ash: 6.9.16
Plant nutrients from plant ash: 9.4
Potassium compounds
Poisons and First Aid: 1.0
Reactions of potassium salts with water: 14.2.1
Solubility in water of different salts: 3.9 (Table)
Sports drinks (electrolytes): 15.8.6
Potassium acetate, (CH3COOK), potassium ethanoate, white crystalline powder, completely dissociated into ions: E261
Potassium adipate, C6H8K2O4, K2C6H80, dipotassium hexanedioate, E357, (acidity regulator, buffer)
Potassium alginate, (KC6H7O6): E402
Potassium alum, "alum"
Potassium aluminium silicate: E555
Potassium amide, Highly toxic, Violent reaction with water, Not permitted in schools
Potassium antinomate, [KSb(OH)6])
Potassium ascorbate, (KC6H7O6): E303
Potassium benzoate, (C6H5COOK), preservative: E212
Potassium borohydride, (BK), white solid, reacts violently with water, toxic
Potassium bromate, (Experiments)
Potassium bromide, (Experiments)
Potassium carbonate, (Experiments)
Potassium chlorate, (Experiments)>
Potassium chloride, (Experiments)
Potassium chromate, (Experiments)
Potassium chromium sulfate
Potassium citrate, K3C6H5O7, hygroscopic, deliquescent: E332
Potassium cobaltcyanide, C6CoK3N6, potassium hexacyanocobaltate
Potassium cyanate, KCNO, toxic if ingested, but not as toxic an cyanides, used as a herbicide, Not permitted in schools.
Potassium cyanide, KCN, Extremely poisonous, Not permitted in schools
Potassium dichromate
Potassium dihydrogen phosphate, (KH2PO4), potassium dihydrogen orthophosphate (V) (in baking powder, buffering agents, nutrient solutions)
Potassium dihydrogen phosphate, potassium phosphate monobasic, For 0.1 M solution, 13.6 g in 1 L water, toxic if ingested
Potassium disulfite, (K2S2O5), potassium pyrosulfite, potassium metabisulfite
Potassium ferricyanide
Potassium ferrocyanide
Potassium fluoride, KF, irritates skin, eyes, mucous membranes, toxic by ingestion, used in insecticides, solder flux and etching glass, Not permitted in schools
Potassium fumarate, C4H2K2O4, #E366 food acid
Potassium hexacyanocolbaltate, C6CoK3N6, potassium cobaltcyanide, toxic if ingested
Potassium hexafluorophosphate, F6KP
Potassium hydrogen carbonate
Potassium hydrogen ethanedioate, potassium hydrogen oxalate
Potassium hydrogen oxalate, C2HKO4, odourless white solid, sinks in water, in many plants, not metabolized, excreted in the urine, used as an analytical reagent
Potassium hydrogen phthalate, KHP, .C8H5KO4, potassium biphthalate
Potassium hydrogen phosphate, (Experiments)
Potassium hydrogen sulfate
Potassium hydrogen sulfite, KHSO3, potassium bisulfite: E326
Potassium phosphate dibasic, K2HPO4. dipotassium hydrogen phosphate, toxic if ingested, used as a buffer: 5.4.3
Potassium hydrogen phthalate, C8H5KO4 .harmful, primary standard to prepare volumetric base solutions, alkali solutions
Potassium hydrogen tartrate
Potassium hydroxide, (Experiments)
Potassium iodate, (Experiments)
Potassium iodide, (Experiments)
Potassium lactate, C3H5KO3, .E326
Potassium magnesium sulfate, K2SO42MgSO4
Potassium malates: E351
Potassium metabisulfite, .K2O5S2: E224
Potassium monoxide, "potash", (K2O), potassium monoxide equivalent in NPK fertilizer, but not (K2O) itself
Potassium niobate, KNbO3, perovskite ferroelectric crystal
Potassium nitrate, (Experiments)
Potassium nitrite
Potassium oxalate, potassium ethanedioate, potassium ethanedioate-1-water, toxic fumes if heated
Potassium oxalate, .C2K2O4, Solution / mixture < 5%, Not hazardous
Prepare: Potassium perchlorate
Potassium periodate, KIO4, ACS reagent
Potassium permanganate, (Experiments)
Potassium peroxymonosulfate, swimming pool: 18.7.49
Potassium persulfate
Potassium phosphate dibasic, harmful if ingested, skin irritant
Potassium phosphates: E340
Potassium propionate: E283
Potassium pyrosulfate, potassium disulfate, (K2S2O7), catalyst, the (S2O72-) ion looks like a dichromate ion
Potassium sodium tartrate
Rochelle salt, (KNaC4H4O6.4H2O)
Potassium sorbate, (C6H7KO2), food preservative and additive E202, inhibits yeast and moulds, allergic reactions
Potassium sulfate
Potassium sulfide
Potassium superoxide, KO2, oxidizing agent, oxygen source
Potassium tartrate, argol, (K2C4H4O6): E336
Potassium tert-butoxide, potassium t-butoxide, (K+(CH3)3CO), (non-nucleophilic base)
Potassium tetraborate, potassium tetraborate tetrahydrate, (K2B4O74H2O), solvent of metallic oxides, lubricant
Potassium tetrachloropalladate, potassium tetrachloropalladium, (Cl4KPd)
Potassium thiocyanate, (KSCN)
Potassium triiodide, (KI3), iodine water, Lugol's solution, (aqueous KI solution + dissolved (I2, I2KI)
Potassium alum
Potassium alum, KAl(SO4)2.12(H2O), "alum"
Alums
Potassium alum, aluminium potassium sulfate, potash alum, potassium aluminium sulfate, aluminium potash, potash alum, harmful
Al2(SO4)3.(K2(SO4).24H2O, (K2SO4.Al2(SO4)3.24H2O
Artificial gemstones, potassium sulfate, aluminium sulfate: 12.10.1
Fireproof cloth: 3.5.11
Kalinite, Aluminium potassium sulfate
Potassium alum and clay suspensions: 7.6.9
Potassium bromate
Potassium bromate, KBrO3, toxic, skin irritant, powerful oxidizing agent, explosive mixture with combustibles
Solution < 0.1%, Not hazardous
Flour treatment agent, effective after making dough: E924
Potassium bromate with propanedioic acid, double autocatalytic reaction, oscillating reaction: 17.3.7
Prepare iodic acid, HIO3, and potassium iodate, KIO3: 12.19.6.3
Potassium bromide
Potassium bromide, Kbr, toxic if ingested, colourless, white, cubic crystals or granules, RD 2.75, MP 730oC
(used in photography, formerly used as a sedative and was supposed to be put in tea of soldiers to control sexual urges).
Potassium bromide is used to prepare bromine water.
For 0.1 M solution, use 12 g in 1 L water.
Potassium carbonate
Potassium carbonate, (K2CO3), (anhydrous or hydrated), skin irritant, toxic if ingested
Lactic acid with potassium carbonate: 16.2.4, (See: Experiment)
Potassium carbonate properties
Potassium carbonate is a white salt, soluble in water, but insoluble in ethanol, to form a strongly alkaline solution.
Commercially it is made by the absorbent reaction of potassium hydroxide with carbon dioxide.
Potassium carbonate has a large capacity to absorb moisture.
Potassium carbonate, anhydrous, "potash" (pearl ash, industrial potassium carbonate), salt of tartar, white, odourless granules, RD. 2.29, MP 891oC (anhydrous is hygroscopic, cakes in moist air): E501
For 0.1 M solution of potassium carbonate, use 13.8 g in water, (soap making, glass making, sourdough).
Potassium carbonate dihydrate, K2CO3.2H2O
Potassium chlorate
Not permitted in schools
Potassium chlorate, KClO3, potassium chlorate (V), potassium perchlorate, chlorate of potash, spontaneous combustion, oxidizing, storage safety problem.
Potassium chlorate and potassium persulfate as oxidizing agents: 15.2.13
Potassium chlorate in pyrotechnic flash powders: 15.2.13.2
Chlorates, hazards (potassium chlorate and manganese dioxide): 3.7.2
Combustible solids, potassium chlorate: 3.5.10
Concentrated sulfuric acid with potassium chlorate, KClO3: 12.19.8.4
Decomposition of chlorates, potassium chlorate: 3.7.4
Gummi bears (gummi fruit) with potassium chlorate: 15.2.13.1
Heat potassium chlorate, manganese dioxide catalyst: 17.3.6
Matches, Safety matches
Sparklers: 15.2.13.3
Storing sodium chlorate and potassium chlorate: 3.4.13.10
Sugar with potassium chlorate, spontaneous combustion: 17.3.4
Potassium chlorate .properties
Potassium chlorate, KClO3, potassium perchlorate, Berthollet's salt, (Claude Berthollet 1748-1822)
It is colourless, white, odourless, monoclinic crystals, RD 2.32, MP 368oC, then decomposes, explodes in contact with sulfur compounds.
It is used in explosives, fireworks and weed killers.
Do NOT use potassium chlorate to prepare oxygen with manganese dioxide catalyst!
Matches. Safety matches
Matches, safety matches: Matches, potassium chlorate
Matchbox: See diagram 3.1.2.6a, potassium chlorate
Potassium chloride
E508 Potassium chloride, KCl
Ice melts, de-icers: 7.4.3.3
Muriate of potash, KCl: 9.17.2.1
Tests for electric polarity, potassium chloride with phenolphthalein: 11.7.1
Potassium chloride .properties
Potassium chloride, KCl, sylvite (sylvine), mineral, muriate of potash fertilizer, white, odourless, cubic crystals or powder, slightly hygroscopic, diet salt substitute, toxic if ingested, extracted from waters of Dead Sea, sold as "lite salt"
Low cost: from supermarkets as "sodium free salt", from garden supply stores as potassium fertilizer
Potassium chromate
Potassium chromate, K2CrO4
Coloured precipitates, double decomposition reactions: 12.2.4.02
Potassium chromate .properties
Potassium chromate, Highly toxic if ingested, carcinogenic, sensitizes skin
Potassium chromate, Solution < 0.5% Not hazardous
Potassium chromate, (K2CrO4, lemon yellow crystals, MP 975oC, alkaline aqueous solution
Potassium chromate, as with other chromium (VI) salts, may be carcinogenic, so handle it with care.
However, when used in dilute solution, near neutral pH, it is relatively safe.
When mixed with acid, chromate ions, CrO42-, first form dichromate ions, Cr2O72-, then chromic acid, H2CrO4.
Solutions containing chromic acid are powerfully oxidizing and highly corrosive.
Do NOT use the cleaning mixture called "chromic acid", prepared by dissolving a metal chromate or dichromate in concentrated sulfuric acid.
This cleaning mixture is NOT permitted in schools, because it is dangerously corrosive to skin and eyes.
It is probably no more effective as a cleaning agent than strong detergent solutions or a suitable solvent.
The reactions of potassium chromate and dichromate with sulfur, carbon, magnesium, aluminium and phosphorus are dangerous. and are NOT permitted in schools!.
Potassium chromium sulfate
Potassium chromium sulfate, KCr(SO4)2.12H2O, K2SO4.Cr2(SO4)3.24H2O, chrome alum, chromium alum, chromium potassium sulfate, alum and mordant, toxic if ingested
Prepare chrome alum: 12.14.4
Properties of chrome alum: 12.14.5
Chromium ions in solution; 12.14.6
Potassium dichromate
Potassium dichromate, K2Cr2O7
Breath test for alcohol using potassium dichromate: 15.2.11
Coloured precipitates, double decomposition reaction: 12.2.1c
Diffusion in liquids: 10.1.2zzz
Extract iodine from kelp: 10.13.2
Glass cleaning with potassium dichromate solution
Potassium dichromate as an oxidizing agent: 15.2.3
Potassium dichromate solution: 2.20.1
Prepare ethanal with potassium dichromate: 16.3.2.7
Prepare potassium dichromate: 12.5.6
Reactions of dichromates, potassium dichromate: 12.5.3
Solubility and temperature, solubility of salts in water: 3.6.7
Solubility of potassium dichromate and temperature: 7.7.6.1
Potassium dichromate .properties
Potassium dichromate, (K2Cr2O7), potassium bichromate (VI), toxic, Corrosive, Oxidizing, Not permitted in schools
Potassium dichromate ACS reagent (Poison, OXD 1479), potassium dichromate (VI)
Potassium dichromate, orange-red crystals, toxic, Corrosive, Oxidizing
Potassium dichromate, For 0.1 M solution, 29.4 g in 1 L water
Low cost: from pottery supply stores, may be called "potassium bichromate"
Potassium dichromate, (K2Cr2O7, potassium bichromate, red prussiate of potash, ferro prussiate, bichrome, orange to red, odourless, monoclinic crystals or granules, RD 2.69, MP 398oC, strong oxidizing agent, toxic and fire risk from oxidation
It was formerly used mixed with sulfuric acid to clean laboratory glassware, but nowadays this procedure NOT permitted in schools.
Oxidation reactions involve the reduction of solutions of chromate or dichromate ions that cause colour changes from yellow or orange to pale green or colourless.
The reactions with the formation of an insoluble metal chromate give brightly coloured precipitates.
Do NOT attempt to isolate these precipitates, because they are carcinogenic.
It is best to prepare these precipitates in the smallest quantities that allow them to be seen.
Do NOT use potassium dichromate solution to colour water for demonstrations.
It is used in machines to breath test for alcohol.
Glass cleaning
Glass cleaning with potassium dichromate solution
Glassware should be clean and dry before use.
When an experiment is completed, the students should discard leftover materials, and rinse all glassware in water.
Cleaning is best done immediately after use as this prevents the staining of work surfaces and the hardening of materials on the glass.
Be Careful! Strong cleaning solvents should be used by the teacher, not by students.
Potassium hydrogen sulfate
Potassium hydrogen sulfate, KHSO4, potassium bisulfate, Toxic if ingested, corrosive to skin and eyes, SO2 formed when heated
Potassium ferricyanide
Potassium ferricyanide, potassium hexacyanoferrate (III), toxic if ingested
Decomposition of ferricyanides, potassium ferricyanide: 3.7.7
Potassium ferricyanide properties
Potassium ferricyanide (III), (K3Fe(CN)6.3H2O, (powder (K3Fe(CN)6), red prussiate, potassium hexacyanoferrate (III), potassium, ferric cyanide, RD 1.89.
It forms attractive ruby red monoclinic crystals, which heat decomposes then melts.
It is used in redox experiments, chemical analysis uses characteristic colour reactions, heating with concentrated sulfuric acid forms carbon monoxide gas It is used in dyeing, etching blueprint paper, case-hardening, fertilizer.
Potassium ferricyanide is Highly toxic, boiling with dilute acids forms cyanide gas.
Potassium ferricyanide with concentrated ammonia solution may explode!
Potassium ferrocyanide
Potassium ferrocyanide, (K4Fe(CN)6.3H2O, potassium ferrous cyanide, potassium hexacyanoferrate (II), potassium hexacyanoferrate (II)-3-water, yellow prussiate of potash, prussiate of potassium
Environment danger, toxic if ingested, yellow monoclinic crystals or powder, RD 1.85, efflorescent, anhydrous at 100oC.
Direct heating of the solid forms cyanogen gas
It is used to detect Fe3+ ions and as a case hardening agent.
Highly toxic, heating with concentrated sulfuric acid forms carbon monoxide gas.
Highly toxic, boiling with dilute acids forms cyanide gas, (CN)2.
Be Careful!, Highly toxic, mixtures with nitrite salts are explosive.
Potassium hydrogen carbonate
Potassium hydrogen carbonate, KHCO3), potassium bicarbonate (impure potassium bicarbonate "American saleratus"), colourless, odourless, white granules, RD 2.17
It is used in buffers, baking powder, aerated waters, antacid medicines, carbon dioxide fire extinguishers, some detergents, laboratory reagent.
Potassium hydrogen carbonate occurs as calcinite mineral.
Potassium hydrogen tartrate
Potassium hydrogen tartrate, (KHC4H4O7), cream of tartar, potassium bitartrate, HOOC(CHOH)2COOK, KO2CCH(OH)CH(OH)CO2H
potassium L-tartrate monobasic, potassium hydrogen L-tartrate, tartaric acid monopotassium salt, potassium hydrogen L-tartrate, tartaric acid monopotassium salt,
potassium bitartrate, potassium hydrogen tartrate, tartar, acid potassium tartrate
argol, tartar
Potassium hydrogen tartrate is a white crystalline acid salt, purified form of brown crystals argol from deposits in wine vats, used in baking powder.
Potassium hydrogen tartrate, acid potassium tartrate, white crystalline acid salt, purified form of brown crystals argol,
It is used in baking powder, and is obtained from deposits in wine vats, also the "crust" in "crusted port", which has finally fermented in the bottle).
Common names: Cream of tartar, Potassium hydrogen tartrate (KHC4H4O7), potassium bitartrate.
Beeswing
Beeswing is the filmy, veined "crust" in old port, which has finally fermented in the bottle.
Common names: Cream of tartar, Potassium hydrogen tartrate (KHC4H4O7), potassium bitartrate.
Potassium hydroxide
Potassium hydroxide, KOH, caustic potash, potash lye, Extremely corrosive to skin, eyes
Potassium hydroxide, Solution > 4M (24%), Extremely corrosive to skin, eyes
Potassium hydroxide, Solution < 4M (24%), Extremely corrosive to skin, eyes
Potassium hydroxide, Solution > 1M (6%), Extremely corrosive to skin, eyes
Potassium hydroxide, Solution < 1M (6%), Corrosive to skin, eyes
Potassium hydroxide, Solution > 0.1M (0.5%), Corrosive to skin, eyes
Potassium hydroxide, Solution < 0.1M (0.5%), Not hazardous
Potassium hydroxide 2 M solution, dissolve 110 g of KOH sticks in 1 L water
Prepare alkalis: 5.3.3
Prepare potassium hydroxide with chlorazol black solution: 6.9
Prepare iodic acid, HIO3, and potassium iodate, KIO3: 12.19.6.3.
Prepare potash alum from its constituent salts: 12.14.1.
Prepare soap: 12.12.1.
Reactions of chlorine with alkalis, bleaching powder: 12.4.15
Respiration is a form of combustion: 8.6.5.
Potassium hydroxide properties
Potassium hydroxide, KOH, caustic potash, lye, potash, white pellets, KOH "sticks" or rods in water, lumps, flakes, sticks.
It is very deliquescent and absorbs CO2and SO2 from air better than sodium hydroxide, because more soluble.
It is used to prepare soft soap and alkaline storage cells.
heat from dissolving in water, potassium lye, damages eyes and body tissues, RD 2.044, MP 380oC: E525.
Potassium hydroxide, KOH, solid, flake, pellets, 1 M analytical reagent, caustic potash
Potassium hydroxide, as a solid or concentrated solution is extremely corrosive to the skin and eyes.
Always wear safety glasses when handling potassium hydroxide, even with dilute concentrations.
If potassium hydroxide enters the eye, rinse the eye instantly with water.
Solutions of potassium hydroxide on the skin feel soapy, because fats in the skin are broken down to form anions of fatty acids, e.g. stearate, palmitate and oleate,
which give the solution a slippery feel.
When potassium hydroxide dissolves in water, a large amount of heat is released.
It sometimes causes the solution to boil violently if it has NOT been stirred, so always stir solutions in that potassium hydroxide is dissolving to dissipate heat and
to provide a uniform concentration throughout the solution.
Potassium hydroxide solutions boil at a higher temperature than pure water.
It is hygroscopic, so keep it in a sealed plastic container.
It is more corrosive to eyes than acids.
Potassium hydrogen phosphate
Potassium hydrogen phosphate, (K2HPO4), dipotassium hydrogen phosphate (V), di-potassium monohydrogen phosphate, di-potassium hydrogen orthophosphate,
microbiology chemical, (K2HPO4), food additive, culture nutrient
Micro-organisms and water pollution: 4.3.11
Prepare solutions of known concentration: 5.4.1.0 (See Dipotassium hydrogen orthophosphate in table).
Buffer reagent, phosphate buffer reagent (potassium hydrogen phosphate): 9.2.25
Potassium iodide
Potassium iodide, KI, Potassium iodide paper, Potassium iodide powder pillows
Potassium iodide, For 0.1 M solution, 16.6 g in 1 L water
Potassium iodide crystals, KI, photography, ingredient of iodized "table salt"
Iodine clock reaction, hydrogen peroxide, potassium iodide: 17.1.6
Potassium iodide with hydrogen peroxide, reverse colour change: 17.3.5
Coloured precipitates, double decomposition reactions: 12.2.1c
Electrolysis of potassium iodide solution, electrolytic writing: 15.5.23
Potassium iodide with potassium iodate (rate of reaction depends on concentration): 17.5.4.2
Prepare iodine solution: 1.6.1
Tincture of iodine, I2
Potassium iodide properties
Potassium iodide, KI, colourless solution, white crystals or granules, RD 3.12, MP 698oC, slightly deliquescent in moist air, bitter taste, separated from potassium iodate by fractional crystallization, becomes yellow when iodine lost to air
It is used in chemical analysis, photography, additive to prepare iodized "table salt" to treat iodine deficiency, e.g. goitre.
It is used in tincture of iodine medicine, solvent for iodine to form the brown triiodide ion I3-, KI3 (aq).
It is used as a test for starch.
It is used to detect presence of Pb2+ ions, when yellow precipitate of lead iodide forms.
If KI solutions become yellow from iodine formation, add sodium hydrogen sulfite solution to make solution colourless again.
Potassium iodate
Potassium iodate, KIO3. potassium iodate (V) powder, potassium iodate (VII), potassium periodate, toxic, may ignite with combustibles or organic compounds.
Prepare iodic acid, HIO3, and potassium iodate, KIO3: 12.19.6.3.
Table salt and rock salt: 19.1.16
Potassium iodate properties
Potassium iodate, white, monoclinic crystals or granules, slightly deliquescent, RD 3.89, MP 560oC, oxidizing agent (ingredient of iodized "table salt", analytical reagent), store out of light.
Potassium iodate is the potassium salt of iodic acid.
It may ignite combustibles or organic compounds and produce toxic fumes.
It has a violent reaction with aluminium, magnesium, carbon, sulfur, phosphorus.
A violent reaction occurs with sodium bisulfite if water added.
Potassium iodate forms toxic fumes with concentrated sulfuric acid.
Potassium nitrate
Potassium nitrate, KNO3, nitre (US niter), saltpetre (US saltpeter), formerly sodium carbonate, potassium nitrate (V), nitrate of potash
Potassium nitrate, colourless crystals or white powder, Preservative E249
For 0.1 M solution, 10.l g in 1 L water, Oxidizing
Ammonium nitrate cold pack: 14.2.4
Black powder, gunpowder, potassium nitrate + sulfur + charcoal
Reactions of ammonium salts and potassium salts with water: 14.2.1
Combustible solids: 3.5.10
Combustion of potassium nitrate, fire line on paper, string fuse: 14.2.6
Decomposition of nitrates: 3.30.4
Low cost: from garden stores as potassium nitrate or "saltpeter" fertilizer, from pottery stores, test reagents
Micro-organisms and water pollution:
Prepare potassium nitrate from manure: 3.9.1.
Potassium nitrate with water: 14.2.5
Prince Rupert's Drops, tempered glass, toughened glass: 34.5.2.9
Refrigerants: 14.2.7
Solubility and temperature, solubility of salts in water: 3.10
Solubility of different salts and temperature: 7.7.5
Potassium nitrate properties
Potassium nitrate, KNO3, "saltpetre", (US saltpeter) (occurs as nitre, niter, Bengali saltpetre), colourless, .odourless, trigonal or rhombic crystals or white granules,
RD 2.11, MP 333oC, strong oxidizing agent that decomposes at 400oC to lose O2
It is used as nitrate of potash fertilizer, fireworks, food preservative, explosives, e.g. gunpowder), food preservative E252.
Potassium nitrate is a powerful oxidizing agent and forms explosive mixtures with most combustible materials.
Potassium nitrate has relatively low toxicity, and can be safely used in aqueous solution.
Do NOT mix potassium nitrate with charcoal, sulfur, red phosphorus or active metals, e.g. Na, powdered Al, Mg, cyanides, sulfides, thiosulfates, ammonium salts,
acetates, household sugar or combustible material,, because these mixtures may be explosive.
The demonstration of explosives is NOT permitted in schools.
If testing production of oxygen from heated solid and lighted splint is accidentally dropped into molten salt, an explosion may occur.
Gunpowder (black powder, black gunpowder), is a mixture of potassium nitrate, charcoal and sulfur, the explosive propellant formerly used in firearms.
, It is now superseded for modern firearms by "smokeless powder", a mixture of potassium salts.
Common names: Saltpetre, saltpeter (used as stump remover, agricultural fertilizer, meat preserver.).
Potassium nitrite
Potassium nitrite, potassium nitrite (III), toxic if ingested
Potassium nitrite, Solution < 1%, Not hazardous
Potassium nitrite, KNO2, white to yellow deliquescent solid, MP 440oC, explodes above 600oC
It is used to detect presence of amino groups inorganic compounds.
It reacts with acids to form toxic nitrogen dioxide gas, that reacts with oxygen in the air to form highly toxic nitrogen dioxide gas.
Potassium perchlorate
Potassium perchlorate, KClO4, toxic, skin irritant, violent explosive mixture with combustible, Not permitted in schools
"Blaster Balls", potassium perchlorate + sulfur, exothermic reaction, (toy product)
Potassium perchlorate should not be used or stored in a school science laboratory.
Prepare potassium perchlorate: 12.19.8.5
Potassium permanganate
Potassium permanganate, KMnO4
Acidified potassium permanganate (VII) reactions, oxidizing agent in titrations: 15.2.4.4
Colour change of diluted potassium permanganate: 11.3.1
Ethanedioic acid-2-water (oxalic acid) with potassium manganate (VII), autocatalysis: 17.3.3
Potassium manganate (VII) oxidizes iron (II) to iron (III): 15.2.4.1
Potassium manganate (VII) oxidizes glycerol to carbon dioxide and water: 15.2.4.2
Potassium manganate (VII) solution liberates chlorine from hydrochloric acid: 15.2.4.3
Potassium permanganate, Condy's crystals (Agriculture): 4.3.2
Movement of ions, potassium permanganate solution: 11.2.1
Oxidation of glycerol by potassium permanganate: 12.12.4
Permanganates, hazards: 3.7.12
Prepare chlorine with hydrochloric acid / potassium manganate (VII): 12.4.1.2
Prepare ethanal with potassium manganate (VII): 16.3.2.2
Prepare oxygen gas with potassium manganate (VII): 3.49.2
Prepare potassium permanganate: 12.8.3
Reduce potassium manganate (VII) with hydrogen sulfide: 3.43.2
Reduce potassium manganate (VII) with sulfur dioxide: 3.51.4
Tests for alcohols, potassium manganate (VII): 16.1.3.1.1a
Tests for saturated hydrocarbons, acidified potassium manganate (VII) solution: 9.4.9.0
Potassium permanganate properties
Potassium permanganate, KMnO4, potassium manganate (VII), Condy's crystals (OXD 1490), Condy's crystals, toxic if ingested
Purple-black rhombic crystals with metallic sheen, RD 2.7, pink-purple solution when dissolved in water.
Heat decomposes crystals with a distinct sweet bitter taste.
Used as a common strong oxidizing agent and disinfectant, also as a chemistry analytical reagent, MnO4- ion.
Potassium permanganate is a powerful oxidizing agent that forms dangerously combustible or even explosive mixtures with oxidizable materials, or combustible
materials, e.g. red phosphorus, cyanides thiosulfates acetates, sugar, charcoal, sulfur, phosphorus, ammonium salts, active metal powders, organic compounds.
The solid is also spontaneously flammable on contact with glycerine, ethylene glycol and other organic compounds.
It forms violently explosive manganese heptoxide on mixing with concentrated sulfuric acid.
Oxygen gas is formed on heating the solid, but toxic fine particles of manganese oxides are produced simultaneously, so if the reaction occurs in a test-tube,
place a plug of glass wool in the end of the tube to trap particles.
Do NOT use sulfuric acid for drying oxygen gas from decomposition of potassium permanganate, because the acid could mix with the salt and react explosively.
For preparing oxygen gas, it is safer to use hydrogen peroxide and potassium permanganate, or hydrogen peroxide with manganese dioxide catalyst.
If potassium permanganate is used for preparation of chlorine gas, by reaction with hydrochloric acid, the solid must be is covered with a layer of water and
hydrochloric acid must is used, NOT sulfuric acid.
Acidified solutions are used as an oxidant in organic chemistry for the oxidation of aldehydes or alcohols.
Neutral solutions are used to distinguish between alkanes and alkenes.
Dilute aqueous solutions of potassium permanganate are relatively harmless and have been used medicinally for mouthwashes and bactericides.
Potassium manganate (VII) is NOT a primary standard, so make up an approximate concentration and titrate it against an ethanoic acid solution of known concentration.
Potassium manganate (VII) crystals are so dark it is difficult to see if all have dissolved when making up a solution.
Bottles of potassium manganate (VII) solution may have a brown precipitate around the top of manganese (IV) oxide.
It is formed when manganate (VII) ions react with water in the air.
It is used to stain wood and furniture.
For water treatment, used for oxidation of Fe2+ --> Fe3+, and Mn2+ --> Mn4+, remove tastes and odours,
disinfectant control nuisance organisms, control DBD (dielectric barrier discharge), of ozone.
Used as topical fungicide and antiseptic.
Solution of 1 g per litre controls powdery mildew and black spot plant diseases.
However, pink staining causes problems.
Potassium permanganate, Solution < 25%, Not hazardous.
Low cost: from aquarium suppliers as crystals or aqueous solution, in test reagents, water purification suppliers.
Potassium persulfate
Potassium persulfate, (K2S2O8), potassium peroxydisulfate, toxic, skin irritant, white crystalline solid, mixture with combustibles burns fiercely, solid decomposes
on standing below 100oC
Potassium sodium tartrate
Potassium sodium tartrate, C4H4KNaO6), potassium sodium tartrate-4-water, sodium potasium L-tartrate
Rochelle salt
Piezoelectricity (voltage produced by mechanical stress to crystals): 32.1.2.1
Hydrogen peroxide with potassium sodium tartrate, cobalt (II) chloride catalyst, visible activated complex: 17.3.1.4
Rochelle salt
Rochelle salt, KNaC4H4O6.4H2O, potassium sodium tartrate tetrahydrate, Seignette salt,
Seidlitz powder, a double salt of tartaric acid
It has a saline cooling taste as a laxative, and the large deliquescent monoclinic crystals are piezoelectric and used in "crystal" phonograph pickups.
Rochelle salt: E337
Prepare Fehling's solution: 9.142.1
Tests for proteins, biuret test: 9.6.5
Potassium sulfate
Potassium sulfate, K2SO4, sulfate of potash fertilizer, .white crystalline powder, prepared with potassium carbonate or potassium hydroxide with sulfuric acid
Potassium sulfate, For 0.1 M solution, 17.4 g in 1 L water: E515.
For chlorine-sensitive plants. use sulfate of potash as source of potassium iron fertilized instead of potassium chloride
Artificial gemstones, potassium sulfate, aluminium sulfates: 12.10.2.6.1
Potassium sulfide
Not permitted in schools
Potassium sulfide, K2S, highly toxic if ingested, releases hydrogen sulfide gas: E225, preservative, antioxidant.
Potassium sulfide, liver of sulfur, sulfurated potash, red-yellow to brown-red, deliquescent, analytical reagent and epilatory, dusts may explode
It is used as a depilatory, hair removing.
Potassium sulfide, liver of sulfur: Alkaline mixture of mainly potassium polysulfides turns silver black.
Potassium thiocyanate
Potassium thiocyanate, KSCN, potassium isothiocyanate, potassium sulfocyanate, toxic if ingested
Potassium thiocyanate, colourless prisms, RD 1.89, MP about 173oC, deliquescent
Potassium thiocyanate, dilute solutions, Not hazardous
Thiocyanate (thiocyanato), S-CN-, monodentate ligand
Group III Insoluble hydroxides, Fe(OH)3, Cr(OH)3, Al(OH)3: 12.11.7.3
3.9.1 Prepare potassium nitrate from manure
1. The mineral form of potassium nitrate, nitre, saltpetre (UK), saltpeter (US) cannot be made in any considerable quantity in less than six or eight months.
Use rotted manure ("black earth"), old mortar or wood ashes mixed with straw.
Each week, add the richest kinds of liquid manure, e.g. urine, dung water, water from privies, cesspools, drain to keep the heap moist, but not wet.
Drain off any superfluous liquid to a tank to be used in later watering the heaps.
Turn the whole heap turned over every month to hasten the process of nitrification.
During the last few months of the process, heaps must be kept moist by water only.
As the heap ripens, the nitre is brought to the surface by evaporation, as a white efflorescence, detectable by the taste.
A more accurate method is by leaching a small quantity of the earth, and boiling to dryness, and weighing the salt.
2. Repeated leaching with water to produce a ley is used to get as strong a solution as possible, and extract most of the nitre.
After the sixth leaching, the earth is considered as sufficiently exhausted.
The leys thus obtained are used upon fresh earth until the solution is of sufficient density to bear an egg when it then contains about a 500 g of salt to 4 litres of liquid.
3. The ley contains, nitrate of potash (nitre, potassium nitrate), nitrate of lime, nitrate of magnesia, sodium chloride and potassium chloride.
To convert all other nitrates into nitrate of potash, add wood ashes.
The potash of the ashes takes all the nitric acid of the other nitrates, forming the nitrate of potash (nitre).
The lime and magnesia are precipitated as an insoluble sediment.
Also, the ashes can be mixed with the nitrified earth and leached together or the saltpetre ley filtered through wood ashes, or the ley of ashes added to the saltpetre ley.
4. Put the ley in a boiler.
The ley still contains common salt (sodium chloride), and other impurities.
However, nitre, is much more soluble than common salt in boiling water, but much less soluble in cold water.
As the boiling proceeds and the solution becomes more concentrated, the common salt is precipitated in small crystals as a sandy sediment to be raked out.
Remove organic matter rising as scum.
Leave the boiler to cool when the concentration has reached almost the point of saturation.
This point is determined by letting fall a drop of the boiling liquid upon a cold metallic surface so that, if it crystallizes quickly, it is time to stop the boiling.
As the ley cools, most of the nitre separates as crystals, which sink to the bottom.
Remove the crystals and return the mother liquor to the boiler, or used in watering the heaps.
The crude saltpetre still contains 15-20% of impurities, mainly sodium chloride, potassium chloride and organic matter.
5. Refining
Starting with saturated solution of nitre, add glue that seizes upon the organic matter and rises as scum to be removed.
Continue the boiling until the liquid is clear, then cooled and constantly stirred until most of the nitre is deposited in very fine, needle-like crystals, called saltpetre flour.
Wash off all adhering mother liquor.
The nitre is now dried by gentle heat and constant stirring, and may be considered quite pure, and fit for the manufacture of gunpowder.
6. Analysis
1. A saturated solution of any salt will not dissolve any more of that salt, but will freely dissolve other salts.
2. Nitre mixed with charcoal and heated is converted into carbonate of potash, but common salt is not affected.
However. if saltpetre is mixed with charcoal alone and then heated the reaction is violent and explosive.
To moderate the violence, the saltpetre is mixed with common salt, which does not interfere with the reaction.
Use one part crude saltpetre, four parts common salt, and one-half part charcoal, heated in an iron spoon, until reaction ceases.
The nitre is now changed into carbonate of potash to be dissolved in water and filtered.
The quantity is estimated by the quantity of sulfuric of known strength necessary to neutralize it completely.
3. A strong hot solution of nitre crystallizes on cooling, and that the temperature at which crystals begin to deposit depends upon how much nitre is in the solution.
In a saturated solution of nitre, one hundred parts by weight of water at 32F contains 13.32 parts of nitre.
12.8.3 Prepare potassium permanganate
1. Potassium permanganate, dark purple crystals, blue metallic sheen, specific gravity 2.7, melting point 240oC, soluble in water, sulfuric acid and acetone
It is used as an oxidizing agent, a disinfectant, as an anti-algal agent, in metal cleaning, in tanning, bleaching, and as a preservative for fresh flowers and fruits.
2. Put 10 g of potassium hydroxide on a sand tray and heat gently to melt.
Add 1 g of potassium chlorate, mixing with a glass rod.
Add 7.5 g of manganese dioxide very gradually and continuing to stir.
When all has been added heat to bright red heat for fifteen minutes.
Leave to cool, break off the melt and grind to a fine powder in a mortar.
Transfer the powder to a 500 mL flask, add 200 mL of water and heat on a gauze.
During the boiling pass carbon dioxide into the solution.
At first the solution is green and contains potassium manganate:.
6KOH + 3MnO2 + KClO3 --> 3(K2MnO4 + KCl + 3H2O
Later it becomes purple potassium permanganate:.
3(K2MnO4 + 2CO2 --> 2KMnO4 + MnO2 + 2(K2CO3)
After boiling for ten minutes let cool and pour off through glass wool in a filter.
Wash the flask and return the filtrate to it.
Boil for a further ten minutes while carbon dioxide passes through, withdraw a drop of solution and place on a filter paper.
If the drop has a green centre continue the process until complete.
Finally cool and filter.
Transfer the solution to a large evaporating basin and evaporate until crystals appear, then set aside to crystallize.
12.14.01 Potassium safety
Potassium metal is banned in many school systems.
Potassium reacts violently with water to form hydrogen gas that may ignite or explode.
Destroy potassium safely with 2-methylpropan-2-ol.
Potassium forms a crust of yellow oxide that may explode when cut.
Use sodium or lithium instead of potassium.
12.14.1 Prepare potash alum
Potash alum, (K2SO4.Al2(SO4)3.24H2O
Aluminium sulfate can form a double salt with the sulfate of a monovalent metal.
With potassium sulfate it forms potash alum, (K2SO4.Al2(SO4)3.24H2O.
In other alums where Na or (NH4) = X, they have the formula: X2SO4.Al2(SO4)3.24H2O.
In other alums, the sulfate of other trivalent metals, Y, are substituted for aluminium sulfate, and they have the formula:.
X2SO4.Y2(SO4)3.24H2O, i.e. X+.Y3+.2SO42-.12H2O.
The molecular weight of potassium sulfate = 174.
The molecular weight of hydrated aluminium sulfate Al2SO4.8H2O = 666.
So equi-molecular weights of these sulfates = 174: 666 = 1.45 g : 5.6 g.
Crystal-growing competitions often use potash alum and require competitors to grow the best single crystal of potash alum judged on the following criteria: clarity, colourlessness, straight and sharp edges, smooth faces, and regular shape.
Experiments
1. Dissolve 1.45 g of potassium sulfate in 15 mL of water.
Dissolve 5.6 g of aluminium sulfate crystals in 20 mL of hot water.
Mix the two solutions and leave until the next day.
Select a crystal with a regular shape and let it to grow in the solution.
Dissolve the rest of the crystals in the minimum of water and leave to form new crystals.
2. Dissolve 1 g of potassium hydroxide pellets in 40 mL of water and add upwards of 1 g of aluminium foil.
When action ceases, excess magnesium must be left over.
2l + 2KOH + 2H2O --> 2KAlO2 + 3H2)
Pour off the liquid and slowly add dilute sulfuric acid to it until litmus paper shows the solution is slightly acidic.
Heat the solution to evaporate it to a small volume, then leave to cool.
Filter off the crystals, then wash and dry them.
2KAlO2 + 4H2SO4 --> (K2SO4 + Al2(SO4)3 + 4H2O
12.14.4 Prepare chrome alum
Chrome alum, KCr(SO4)2, (K2SO4.Cr2(SO4)3.24H2O, Cr2(SO4)3.(K2SO4.24H2O
1. Reducing action of ethanol on potassium dichromate in acid solution.
Heat 7.5 g of potassium dichromate (VI) in 50 mL of water and leave to cool.
Add 6 mL of concentrated sulfuric acid, stand in ice and stir with a thermometer until cooled to 35oC.
Slowly add by drops 5 mL of ethanol and keep stirring so temperature remains below 50oC.
Leave the solution until the next day in a refrigerator.
Separate crystals from the remaining solution, wash with deionized water and dry with filter paper.
Choose a good crystal to grow in the solution of potash alum to form an overgrowth.
(K2Cr2O7 + 4H2SO4 + 3CH3CH2OH --> (K2SO4 + Cr2(SO4)3 + 7H2O + 3CH3.CHO (acetaldehyde).
Cr2O72- + 8H+ + 3CH3CH2OH --> 2Cr3+ + 7H2O + 3CH3.CHO (omitting the spectator ions)
2. Dissolve 60 g of potassium chromium sulfate in 100 ml water.
Stir common alum (aluminium potassium sulfate) into warm water until it will no longer dissolve.
Mix the two solutions to form deep violet-blue crystals.
Use a seed crystal in a saturated solution of chrome alum to form large diamond-shaped crystals, similar to potash alum.
3. Mix same molar concentrations of solutions of potassium sulfate and chromium (III) sulfate.
Allow to crystallize from a saturated solution on a piece of weighted cotton.
If the solution is evaporated instead of leaving for crystallization, a mixture of crystals of potassium sulfate and chromium (III) sulfate forms.
12.14.5Properties of chrome alum
Chrome alum, potassium chromium (III) sulfate, chromium (III) potassium sulfate,
chromium (III) potassium sulfate-12-water, chromium (III) potassium sulfate dodecahydrate
It is a potassium double sulfate of chromium with formula [Cr2(SO4)3, (K2SO4, 24H2O], [(K2SO4, Cr2(SO4)3, 24H2O], [CrK(SO4)2, 12H2O], so it is similar to potash alum.
It can be used in dyeing and in tanning leather.
12.14.6Chromium ions in solution
Chromium ions in solution, [Cr(H2O)6]3+
Chrome alum crystals are soluble in water to form an violet-blue acid solution, about pH 3.
2. Boil a dilute solution of chrome alum in a test-tube
The violet-blue colour of the solution turn green, but when allowed to cool and stand, the violet-blue colour returns.
3. Add washing soda solution, Na2CO3.10H2O, to a violet-blue solution of chrome alum in a test-tube.
A light green gelatinous precipitate of the hydrogen carbonate forms or a light blue precipitate forms with bubbles of carbon dioxide.
Add drops of hydrogen peroxide to the test-tube and boil the contents.
A yellow solution of sodium chromate forms.
Filter paper wetted with the yellow solution turns green in sulfur dioxide gas.
4. Add dilute ammonia to a solution of chrome alum.
A light green precipitate of chromium hydroxide forms.
This precipitate, like aluminium hydroxide, has a great attraction for dyes and is used as a mordant to make dyes stick to cloth.
Add small amount of ammonia.
Cr(H2O)63+ --> Cr(H2O)3(OH)3)
Blue chrome alum --> light green neutral complex of chromium hydroxide
Add excess ammonia that replaces water as a ligand.
Cr(H2O)3(OH)3 --> Cr(NH3)63+
Light green chromium hydroxide --> violet hexaamminechromium (III) ion
(in test-tube violet over green precipitates)
5. Oxidize chromium (III) ions to chromium (VI) ions
Add excess sodium hydroxide solution to hexaaquachromium (III) ion solution to form green hexahydroxochromate (III) ion solution.
Cr(H2O)63+ --> Cr(H2O)3(OH)3)
Heat with hydrogen peroxide solution to form bright yellow chromate (VI) ion solution.
15.2.4.1 Potassium permanganate (VII) oxidizes iron (II) to iron (III)
Add potassium permanganate solution and drops of dilute sulfuric acid to iron (II) sulfate solution.
The manganate (VII) ions (MnO4-) are reduced to manganese (II) ions (Mn2+).
The iron (II) ions (Fe2+) are oxidized to iron (III) ions (Fe3+).
MnO4- (aq) + 8H+ (aq) + 5e--> Mn2+ (aq) + 4H2O (l)
5Fe2+ (aq) --> 5Fe3+ (aq) + e-
MnO4- (aq) + 8H+ (aq) + 5Fe2+ (aq) --> Mn2+ (aq) + 4H2O (l) + 5Fe3+ (aq)
Under alkaline conditions, MnO2 is precipitated, a reaction used in water treatment.
MnO4- + 2H2O + 3e- --> MnO2 + 4OH-
15.2.4.2 Potassium permanganate (VII) oxidizes glycerol
Put 3 g of fine crystal potassium permanganate on a coffee in lid on sand.
Make a hole in the centre of the potassium permanganate and pour 1 mL glycerol (propane-1,2,3-triol) into the hole.
Boil then cool the glycerol first if it has already absorbed water.
Observe a bright pink flame and steam given off.
Dissolve the residue in water and note a green solution [Mn (VI)] and brown solid [Mn (IV)].
15.2.4.3 Potassium permanganate liberates chlorine from hydrochloric acid
Do this experiment in a fume cupboard.
Add potassium permanganate solution to 2 cm of concentrated hydrochloric acid solution in a test-tube with damp filter paper over.
the edge of the opening.
Chlorine gas is given off.
Be careful! The damp filter paper becomes bleached.
2MnO4- (aq) + 16H (aq)+ + 10Cl- --> 2Mn2+ (aq) + 8H2O (l) + 5Cl2 (g)
10Cl- (aq) - 10e- --> 5Cl2 (chloride ion oxidized)
2MnO4- (aq) + 16H+ (aq) + 10e- --> 2Mn2+ (aq) + 6H2O (l) (permanganate ion reduced)
15.2.4.4 Acidified potassium permanganate (VII) reactions
Potassium permanganate (VII) is an oxidizing agent in titrations.
1. Prepare acidified potassium manganate (VII) solution by mixing 10 mL of 0.02 M potassium manganate (VII) solution with 20 ml of dilute sulfuric acid.
It is an oxidizing agent and irritating to the skin and eyes.
Wash any splashes off the skin.
It should be diluted further to give a pale pink solution to ensure that decolorization occurs readily.
For disposal, add sodium metabisulfite with stirring to the acidified potassium manganate (VII) solution residue until the solution is colourless.
Flush to foul water drain.
2. Put potassium manganate (VII) solution in the burette.
Put the other solution in the receiving flask, acidified with dilute sulfuric acid, not hydrochloric acid.
Potassium manganate (VII) becomes colourless as it drops into the solution in the receiving flask until at the end point a slight trace of permanent pink solution
indicates excess of manganate (VII) ions.
The half equation for manganate (VII) ions in acidic solution:
MnO4- (aq) + 8H+ + 5e- --> Mn2+ (aq) + 4H2O (l)
3. Acidified potassium manganate (VII) solution oxidizes:
3.1 Iron (II) ions to iron (III) ions
Fe2+ (aq) --> Fe3+ (aq) + e-
5Fe2+ (aq) + MnO4- (aq) + 8H+ (aq) --> 5Fe3+ (aq) + Mn2+ (aq) + 4H2O (l)
3.2 Hydrogen peroxide solution to oxygen
H2O2 --> O2 + 2H+ + 2e-
3.3 Ethanedioic acid to carbon dioxide (using much heat)
(COOH)2 --> 2CO2 + 2H+ + 2e-
3.4 Sulfate (IV) ions [sulfite ions] to sulfate (VI) ions [sulfate ions]
SO32- + H2O --> SO42- + 2H+ + 2e-
However, potassium manganate (VII) solution cannot be used in solutions containing ions it can oxidize, e.g. Cl-, Br-.
Pyrocatechuic acid
Pyrocatechuic acid, C7H6O4
Pyrocatechuic acid, (2,3-Dihydroxybenzoic acid), (derived from benzoic acid), irritant, plant metabolite, human metabolite
It occurs in plasma after consumption of cranberry juice or aspirin, causes facial pain due to stress.
It occurs in Phyllanthus acidus, in Salvinia molesta (aquatic fern).
Platinum, Pt
See Platinum Table of Elements
Platinum (Commercial)
Platinum, Table of the Elements
See Platinum, RSC
Platinum is a soft, ductile transition metal, resists most chemical agents, does not oxidize at high temperature, available as foil and wire.
It occurs in free elemental form placer deposits or in alloys, and is used for electrical contacts electrodes and jewellery.
Platinum has no reaction with dilute HCl or H2SO4, air, water or concentrated oxidizing acids, e.g. HNO3 or H2SO4, reacts with aqua regia, (concentrated HNO3 + HCl) to form H2PtCl6.
Platinum is malleable, ductile and can be cut into slices.
It has a slightly grey lustre.
It is harder than gold and silver, so it is mixed with those metals when making rings and other jewellery.
Platinum vessels can hold acids, because they do not react with them.
Platinum was first used for decorative objects and jewellery settings, but nowadays is used in scientific apparatus, electrical equipment, electrodes and resistance thermometry and many industrial processes as a catalyst.
It has weak magnetism.
Platinum black is used as a catalyst in chemical reactions.
Platinum can absorb hydrogen and is used in catalytic converters to treat exhaust gases of motor vehicles.
The melting point of platinum is 1768oC, higher than gold, bronze and iron.
It was used to cast the platinum-iridium cylinder called the International Prototype Kilogram (IPK), in France, because of its high density and resistance to corrosion.
A "platinum" record has sold one million copies.
Atomic number,78, Relative atomic mass,195.08, r.d. 21.4, MP = 1769oC, b.p. = 4530oC
Platinum, Pt (Spanish plata silver, because platinum has silvery colour), platinum wire, 0.375 mm diameter, loop for inoculation of microbial cultures, possibly sensitizes skin, powder Platinum Group of Metals (PGMs), jewellery plating industry term for "4 PGM's,platinum, rhodium, osmium, ruthenium, iridium".
Chloroplatinic acid
Platinum (IV) chloride. Platinum (IV) oxide
Specific heat capacity,134 J kg-1 K-1
Platinum, natural platinum,35.2.54, (Geology)
Catalytic converter in a car,7.9.13.1
Catalytic oxidation of ammonia forms nitrogen monoxide, with red-hot platinum wire,13.6.6.1
Chloroplatinic acid
Platinum (IV) chloride, PtCl4
Platinum (IV) oxide, platinum dioxide, P2O2
Adams's catalyst, platinum oxide hydrate, PtO2.H2O, organic hydrogenation catalyst
Platinum, Pt, (Spanish plata silver, platinum has silvery colour), platinum wire, 0.375 mm diameter, loop for inoculation of microbial cultures, possibly sensitizes skin, powder.
Platinum Group of Metals (PGMs), is the jewellery plating industry term for "4 PGM's, platinum, rhodium, osmium, ruthenium, iridium".
Chloroplatinic acid, hexachloroplatinic acid, H2PtCl6, H2PtCl6.(H2O)6, [H3O]2[PtCl6].4H2O, platinic chloride PtCl4]
Platinic chloride, chloroplatinic acid, Platinum (IV) chloride, Platinum (IV) oxide
Pyrogallol
Pyrogallol, C6H3(OH)3, benzene-1,2,3-triol, 1,2,3-trihydroxybenzene, pyrogallic acid, Highly toxic if ingested, corrosive to skin.
Pyrogallol,Pyrogallol
Germination and air,9.118
Test gas collected in a respirometer,9.6.12
toxicity, Poisons and First Aid,3.10.0
Pyrrolines
Pyrrolines, C4H7N, Cyclic Amines, dihydropyrroles, isomers differ in position of double bond 1-Pyrroline (3,4-dihydro-2H-pyrrole), cyclic imine, colourless, less dense than water, soluble in water and alcohol, strong ammonia smell like shrimp seafood.
2-Pyrroline, cyclic amine, 3-Pyrroline, cyclic amine
Red phosphorus, P4
(Greek phosphoros Morning star) (Discovered by Henning Brand, Germany, 1669), light from phosphorus is caused by combustion of oxides on its surface when exposed to air.
Red phosphorus, brown phosphorus, P4, is not poisonous, ignites above 300oC, has phosphorus atoms bound in a covalent network, so is less reactive than white phosphorus and can be stored in air.
It is used in "safety match" striking surfaces that contain red phosphorus, powdered glass, carbon black, a binder and a neutralizer, e.g. calcium carbonate.
It is used for "doping" semiconductors.
Red phosphorus is relatively harmless compared with the white phosphorus allotrope.
However, some school systems do not allow red phosphorus to be used in school science experiments.
It is not poisonous when pure.
It is deliquescent, so keep it in a sealed container.
Do not heat red phosphorus in a test-tube, because it produces phosphorus vapour that condenses to form white phosphorus.
Red phosphorus forms violently explosive mixtures with oxidizing agents, e.g. metal nitrates (potassium nitrate, sodium nitrate, potassium permanganate), nitric acid, chlorates, perchlorates, peroxides, peroxy salts.
Do not heat red phosphorus on a platinum wire, because it corrodes the platinum.
P (red) Atomic number,15, Relative atomic mass,30.9738, RD 2.34, MP 590oC, BP = 280oC, Specific heat capacity,670 J kg-1 K-1
White phosphorus, P4
White phosphorus (yellow phosphorus), P4, is too reactive to be used in school science teaching, so it is not permitted in schools.
In 1943, tonnes of white phosphorus in incendiary bombs were dropped by Allies' air forces on Hamburg, Germany.
White phosphorus is waxy, poisonous, spontaneously flammable, reacts with oxygen gas in the air to form P2O5, so it is stored under water.
White phosphorus is extremely toxic.
On contact with iodine it ignites, with bromine it explodes, and it can be ignited with a hot glass rod.
Cover spilt white phosphorus with 0.2 M copper sulfate solution that converts it to harmless copper sulfide.
P (white) Atomic number,15, Relative atomic mass,30.9738, RD. 1.82, MP = 44.2oC, BP = 44oC, Specific heat capacity,757 J kg-1 K-1
Pipettes
Pipettes (Commercial)
Pipettes, Handling and transferring chemicals,3.4.10 (Safety)
Pipettes, Danger of using pipettes in the laboratory,1.25 (Safety)
Pipettes, Microbiology,4.4.2 (Safety)
Purpureacin
Purpureacin-1, Bullatanocin, Bullatalicin, Squamostatin C, C37H66O8, a polyketide, antifungal, insecticidal
It occurs in Annona purpurea leaves.
Pyridoxine
Pyridoxine, vitamin B6, Pyridoxol, Adermine, Gravidox, C8H11NO3, a hydroxymethylpyridine, converted to a co-enzyme, pyridoxine is the 4-methanol form of vitamin B6, animals must obtain it through their diet.
Vitamin B6 is the term for pyridoxine, pyridoxal, and pyridoxamine and their three phosphorylated derivatives, but "vitamin B6" is commonly used for only pyridoxine.
Pyridoxine is used to treat vitamin B6 deficiency and commercial product Diclectin used to treat nausea and vomiting in pregnancy.
Commercial medicines may contain "pyridoxine hydrochloride equivalent to pyridoxine (Vitamin B6)".
Pyrolysis
Pyrolysis is decomposition caused by heat.
It usually involves a chemical change caused by the application of heat.
Charcoal production is by cutting naturally growing trees and undergoing a process called pyrolysis, which involves heating wood in absence of oxygen.
A mixture of liquid, gas and charcoal is produced.
The process takes about 7 to 12 days in traditional kilns, where 8 to 12 kg of wood are used to produce 1 kg of charcoal.
With the above inefficiency in the production and the growing usage of charcoal suggests that greenhouse gas emissions associated with charcoal could reach 15 billion tonnes of carbon dioxide by 2050, which will be released into the atmosphere leading to climate change.
Perindopril
Perindopril, C19H32N2O5
Perindopril, "Coversyl", ACE (angiotensin converting enzyme), blood pressure inhibitor
Pederindopril erbumine, C23H43N3O5, Perindopril tert-butylamine
An antihypertensive agent and a peptidyl-dipeptidase A inhibitor, used in patients with hypertension and heart failure.
Phosphorescence
"Glow in Dark Sheet and Pen", UV light pen on GID phosphorescent sheet, (toy product)
"Glow Jumping Putty", phosphorescence (toy product)
Phosphorescence is the green glow from the slow oxidation of white phosphorus, an example of chemiluminescence.
However, the term phosphorescence is also used to describe a situation when the luminescence persists although the exciting cause has been removed.
A phosphorescent material irradiated with UV light will emit light of a lower energy for an appreciable interval of time.
If a phosphorescent powder is irradiated with another fluorescent material, when the radiation source is removed the phosphorescent powder emits light for tens of seconds.
Marine phosphorescence is not caused by phosphorus, but by chemical reactions in bioluminescent bacteria.
However, rotting herring glows, caused by combustion of rotting products, Diphosphane, P2H4.
Phosphorescent minerals continue to emit light after the ultraviolet light ceases.
Europium, Eu
Yttrium, Y
Terbium, Tb