School Science Lessons
(UNChem1b)
2024-12-24
Ammonia
Please send comments to: j.elfick@uq.edu.au
Contents
3.1.0 Ammonia
3.6.0 Ammonium compounds
3.2.0 Ammonia gas, NH3, ammonium ion, NH4+
3.3.0 Ammonia reactions
3.4.0 Ammonia solution
3.7.0 Prepare ammonia and ammonium compounds
3.5.0 Tests for ammonia
3.8.0 Cloudy ammonia
3.9.0 Uses of ammonia
3.1.0 Ammonia, (NH3)
See: Ammonia Elements, Compounds, (Commercial).
See ammonia: 12.4.0, Gas, Molecular weight, Density, (Table 1)
Ammonia anhydrous, NH3, ammonia liquefied gas, ammonia gas
Ammonia, aqueous 28% to 30%, aqueous ammonia, aqua ammonia, ammonia water
"Ammonia (total)"' refers to the mixture of ammonia, NH3, and the ionized form (NH4 + ).
Ammonia is less dense than air, 0.769 kg/m3 at STP, so it lighter than air, but vapours from a leak initially hug the ground.
Ammonia solution is a weak electrolyte, so the properties of the molecules and the ions in the solution affect its properties.
The (NH3) compound is the volatile, potentially hazardous, substance present in the mixture.
Ammonia is a colourless gas with a distinct, pungent odour that is distinctive of drying urine.
Ammonia is easily liquefied under pressure.
Ammonia is alkaline and is corrosive to copper.
Ammonia reacts strongly with oxidizers, acids, halogens, and attacks copper, aluminium, silver, zinc and their alloys, and some plastics.
Ammonia is very soluble in water, chloroform and ether, soluble in alcohol and is a good solvent.
Ammonia is toxic if at high levels with increased pH to animals, birds, and fish caused by the (NH3).
Ammonia is formed naturally by the decomposition of urine and manure.
Ammonia is an invisible, extremely irritating gas with a choking smell and is flammable in the presence of sufficient oxygen.
Do not prepare ammonia in an open room, but use a fume cupboard.
Ammonia is extremely irritating to the nose and lungs.
Ammonia absorbs impurities on charcoal
Ammonia cell test kit (0.2-10 mg / litre)
Ammonia cell test kit (1-28 mg / litre)
3.9.0 Uses of ammonia
* Ammonia is used in household and industrial cleaners, bleaching agents and disinfectants
* Ammonia is used in the preparation of synthetic fibres, e.g. nylons), plastics and explosives, resins, medicines, fertilizers, fuel cells and in refrigeration.
* Ammonia is used in smelling salts, household and industrial cleaners, and window-cleaners
* Ammonia is used as a fertilizer, as a refrigerant, and in the manufacture of other chemicals.
* Household use of ammonia solution, in the soapy wash water, to loosen dirt, add whiteness and prevent shine, remove burnt food in aluminium pans,
clean tops of stoves, remove fruit juice stains.
* Ammonia is used in tests for aldehydes, Tollens' test, 9.8.4 (ammonia solution)
E150c Ammonia caramel, (colouring agent)
E150d Sulfite ammonia caramel, (colouring agent)
3.2.0 Ammonia gas, NH3, ammonium ion, NH4+
Ammonia is a colorless gas with a pungent odour, said to smell like decaying fish.
Ammonia occurs naturally in the environment, and bacteria in the human intestine produce ammonia.
Hot ammonia gas is a reducing agent, e.g. hot black copper oxide is reduced to copper by a stream of hot ammonia.
Ammonia forms complex ions with metallic ions, e.g. cuprammonium sulfate, (IUPAC Tetraamminecopper(II) sulfate monohydrate), [Cu(NH3)4]SO4·H2O.
Ammonia dissolves in water to produce clear colourless ammonia solution, liquid ammonia, aqueous ammonia, NH3 (aq), ("ammonium hydroxide"),
which is mainly undissociated, but contains enough hydroxyl ions to behave as a weak alkali.
NH3 + H2O --> NH + 4 + OH −
ammonia + water --> ammonia solution
The reaction does not form [NH+4][OH−]
Ammonia solution is a very weak acid.
The ammonium ion, NH4 + , is stable and has a metallic character.
When heated with a high concentration of hydroxyl ions, the ammonium ion forms ammonia gas.
NH4+ + OH- --> NH3 (g) + H2O
By hydrolysis, ammonium salts may react acidic.
NH4+ + H2O --> NH4OH +H +
Ammonium salts sublime when heated.
Ammonia can be deprotonated in non-aqueous solutions to give the amide ion NH2-, and you can buy sodium amide.
2Na + 2NH3 --> 2NaNH2 + H2
sodium + ammonia --> sodium amide + hydrogen
Sodium amidem sodamide, sodium azanide is used as an organic chemistrystrong base, e.g for production of indigo dye for blue jeans, C16H10N2O2.
3.3.0 Ammonia reactions
Ammonia, anhydrous hazards: 3.8.1
Ammonia with copper oxide (redox reaction): 12.2.6.3
Ammonia with copper sulfate: 3.3.1
Ammonia with copper sulfate solution: 3.3.2
Ammonia with cobalt chloride solution: 3.3.3
Ammonia with sulfuric acid (acid-base neutralization): 12.8.1
Catalytic oxidation of ammonia, with red-hot platinum wire: 3.3.4
Catalytic oxidation of ammonia, with chromium (III) oxide: 3.3.5
Catalytic oxidation of methyl alcohol, and ammonia solution: 17.3.2
Diffusion rates of ammonia and hydrogen chloride gases: 10.1.2
Hartshorn
Liquid ammonia, anhydrous ammonia fertilizer: 9.17.3
Magnesium sulfate with ammonia: 12.4.10
QAC (quaternary ammonium compounds), swimming pools: 18.7.56.0
Reactions of ammonium salts and potassium salts with water: 14.2.1
Reduce copper (II) oxide to copper with ammonia: 3.3.6
Reduce nitrates to ammonia: 12.11.2.2
Storing alkalis, ammonia solution: 3.3.2
Tests for hydroxyl ions (hydroxide ions), ammonia solution: 3.3.7
Tests for hydrogen chloride with ammonia solution: 3.3.8
Tests for ammonia: 3.5.0
3.4.0 Ammonia solution
[NOT "ammonium hydroxide, NH4OH".]
Ammonia solution is shown as (NH3) (aq), because "(NH4) + " ions and "(OH) - " ions can be detected, but not "(NH4OH)".
Ammonia solution, aqueous ammonia, spirits of hartshorn, Toxic by all routes, Lung & eye irritant
3.8.1 Ammonia, anhydrous, hazards
Ammonia solution (10% ammonia solution): 5.3.4
Ammonia solution < 2 M, ammonium hydroxide, < 5%, Not hazardous, --> 18 M, 35-50%, --> 50%, 2-5 M, 5-10%
Ammonia solution 3 M: dilute 200 mL (28%) 14.8 M concentrated solution to 1 litre of water
Ammonia solution 4 M: dilute 220 mL (28%) 18 M concentrated solution to 1 litre of water ("ammonium hydroxide")
Ammonia solution 5-18 M, 10-35%, ammonium hydroxide, cloudy ammonia
Ammonia solution, concentrated, solution 35% w / w, "880" ammonia, concentrated, liquor ammonia fort
Ammonia solution, For 2 M solution, dilute 330 mL of 10% soln in 1 L water
Ammonia solution in a neutralization reaction: 3.31
Ammonia solution test for hydrogen chloride: 3.3.8
Ammonia solution: Ammonium hydroxide (-->25% in water), solution of ammonia in water, ammonia hydrate
Ammonia solution: Ammonium hydroxide, prepare by mixing household ammonia cleaner with water.
Ammonia solution
Ammonia solution, ammonium hydroxide, (NH3), (weak ammonia, about 10%, is sold as a household cleaner)
Ammonia solution is a weak electrolyte so the properties of the molecules and the ions in the solution affect its properties.
Concentrated ammonia solution forms ammonia gas whenever the container holding it is opened.
Ammonia solution
If ammonia solution is spilt in a fume cupboard, evacuate the area until the ammonia fumes have dispersed.
Do not allow ammonia solution to contact the skin.
Do not add concentrated ammonia solution to solid iodine, because a black solid, called touch powder, (NI3NH3) forms.
If dry, the slightest friction causes touch powder to explode.
Do not add concentrated ammonia solution to bleach or bleaching powder, because nitrogen trichloride, (NCl3), may form.
It may form as a violently unstable liquid that may explode.
Common name: Household ammonia, 10% solution, ammonium hydroxide, (NH4OH), is a strong solution of the gas used for cleaning.
Common name: Strong ammonia is a 27% solution.
Ammonia solution is used for neutralizing acids and for precipitating hydroxides of metals, usually as jelly-like precipitates.
They are formed when ammonia is added to solutions of soluble compounds of the metals.
For example. alum (aluminium potassium sulfate), iron alum, (iron (III) ammonium sulfate), magnesium sulfate, and zinc sulfate.
Household ammonia is far too strong for most school experiments.
Instead, prepare a dilute solution by adding about five parts of water to one part of household ammonia.
Prepare a dilute solution by adding about five parts of water to one part of the strong solution.
The gas dissolves in water to form an alkali.
3.5.0 Tests for ammonia
Ammonia fountain test: 3.1.6
Litmus tests for ammonia: 3.1.3
Nessler's reagent test for ammonia: 3.1.7
Odour tests for ammonia: 3.1.2
Sodium bicarbonate test for ammonia: 3.1.5
Solubility tests for ammonia: 3.1.4
Tests for ammonia, ammonium ions: 12.11.3.11
Tests for ammonia or amino acids or proteins with ninhydrin: 10.2.9
Tests for ammonium compounds: 3.1.8
Tests for ammonia, ammonium ions: Nessler's reagent
3.6.0 Ammonium compounds
Ammonium ion (NH4) +
Ammoniacal silver nitratem Ag(NH3)2OH, Tollens' reagent,
Ammonium acetate, CH3CO2NH4, ammonium ethanoate, used for buffers
Ammonium acetate, Low cost production: Drops of ammonia solution with white vinegar until red to litmus paper
Ammonium alum, AlNH4(SO4)2.12H2O, aluminium ammonium sulfate (VI)-12-water, Tschermigite mineral
Ammonium alum: Alums
Ammonium benzoate, C6H5CO2NH4
Ammonium bicarbonate, NH4HCO3, ammonium hydrogen carbonate, white crystals, crystal ammonia, food additive, used in some baking powders.
Ammonium bromide, NH4Br, used in smelling salts
Ammonium carbonate
Ammonium chlorate, NH4ClO3, colourless crystals, Toxic, Explosive
Ammonium chloride
Ammonium chromate, NH4)2CrO4, yellow monoclinic crystals, decomposes at 185 o C, loses ammonia gas, alkaline solution, needs cool storage.
Ammonium copper (II) chloride tetramine copper (II) chloride
Ammonium dichromate
Ammonium dihydrogen phosphate, (NH4)(H2PO4). ammonia dihydrogen orthophosphate (V), ammonium biphosphate, Harmful if ingested.
It is used in agricultural fertilizers and in piezoelectric crystals for microphones and transducers
Ammonium ethanoate, CH3CO2NH4, ammonium acetate, spirit of Mindererus, food acid
Ammonium ferric citrate, ferric ammonium citrate (from citric acid), (food acid) (dietary iron supplement) (in breakfast cereals, diet formulae), E381
Ammonium hexafluorovanadate, ammonium hexafluoridovanadate (V), NH4)3VF6
Ammonium hydrogen carbonate, NH4HCO3, ammonium bicarbonate, Smelling salts (ammonium carbonate): 12.16.3.5
Ammonium hydrogen carbonate: Baking powder
Ammonium hydrogen phosphate, diammonium hydrogen phosphate, (NH4)2HPO4, in fertilizers, Toxic if ingested
Ammonium iodide, Harmful if ingested
Ironammonium sulfate, Mohr's salt
Ammonium iron (II, III) phosphate, NH4Fe2(PO4)2, containing Fe II and Fe III, is the first example of a mixed-valence ammonium iron phosphate.
Prepare ammonium iron (II) sulfate, Mohr's Salt: 12.14.3
Prepare ammonium iron (III) sulfate solution: 12.1.6.1
Ammonium iron (III) sulfate: 12.1.6
Ammonium magnesium phosphate, struvite mineral (NH4)MgPO4.6H2O, (used in phosphate recycling from sewage)
Ammonium metavanadate, ammonium vanadate, NH4VO3
Ammonium molybdate
Ammonium nickel (II) sulfate 6H2O, Harmful if ingested
Ammonium nitrate
Ammonium nitrite, Prepare nitrogen gas, (ammonium nitrite): 3.46
Ammonium oxalate
Ammonium perchlorate, Toxic if ingested, Explosive, Not permitted in schools
Ammonium persulfate
Ammonium phosphate
Ammonium sodium hydrogen phosphate (V)-4-water, Na(NH4)HPO4.4H2O, ammonium sodium hydrogen orthophosphate, microsmic salt (from urine)
Ammonium purpurate, C8H8N606, (Murexide)
Ammonium sodium hydrogen phosphate (V)-4-water, Na(NH4)HPO4.4H2O, ammonium sodium hydrogen orthophosphate, microsmic salt (from urine)
Ammonium sulfate (NH4)2SO4
Ammonium sulfamate, H6N2O3S, herbicide for difficult weeds, Toxic
Ammonium sulfide solution (-->20% in water) (10% solution) (20% solution), Highly toxic fumes
Ammonium tartrate (NH4)2C4H4O6, Ammonium tartrate dibasic, "BioXtra", nitrogen source for biology experiments
Ammonium thiocyanate, NH4NCS, Highly toxic fumes, white yellow, monoclinic, deliquescent crystals, M P 16 o C, test for ferric iron, in fixatives and explosives.
Ammonium thioglyconate C2H7NO2S, ammonium mercaptoacetate, "perm salt", (acetic acid, mercapto-, monoammonium salt), thiofaco A-50, the salt of thioglycolic acid and ammonia, corrosive, acute toxic, irritant
Ammonium thiocyanate, Tests for iron: 12.11.3.20
Ammonium thiosulfate, diammonium thiosulfate (NH4)2S2O3, photography rapid fixer, fertilizer, reducing agent, Environment danger
Ammonium triiodide, nitrogen triiodide: 12.19.6.13
Ammonium vanadate, ammonium metavanadate, Harmful if ingested
Diammonium copper (II) sulfate (VI)-6-water, ammonium cupric sulfate
Diammonium hydrogen phosphate, ammonium phosphate dibasic
Ferrous ammonium sulfate, Mohr's salt: Ammonium iron (II) sulfate
Reactions of ammonium salts and potassium salts with water: 14.2.1
Tri-ammonium citrate (food acid, acidity regulator) (Health risk, liver and pancreas problems), E380
3.7.0 Prepare ammonia and ammonium compounds
Prepare ammonia gas: 3.0
Prepare ammonia, Haber process: 3.01
Prepare ammonia solution: 5.3.4
Prepare ammonium chloride sunbeam mists: 7.8.2.1
Prepare ammonium iron (II) ammonium sulfate, Mohr's salt: 14.8.14
Prepare ammonium iron (II) sulfate, Mohr's salt: 12.14.3
Prepare ammonium iron (III) sulfate solution: 12.1.6.1
Prepare ammonium nitrate: 3.7
Prepare ammonium sulfate by neutralization: 12.14.1
Prepare chrome alum: 12.14.4.0
Prepare hydroxides with ammonia solution: 3.2.1
Prepare hydroxides by precipitation: 12.1.33
Prepare iron (II) ammonium phosphate: 12.14.2
Prepare iron (III) ammonium alum: 12.13.7
Prepare rayon, copper (II) sulfate with ammonia solution: 3.4.8.0
Prepare rayon, basic copper carbonate with ammonia solution: 3.4.8.1
3.8.0 Cloudy ammonia
Cloudy ammonia, household ammonia, contains powdered soap in addition to ammonia.
It is used as a heavy duty general cleaner and floor cleaner to strip wax from floors.
Ammonium carbonate NH4)2CO3
Ammonium carbonate with acids: 12.12.3
Ammonium carbonate with alkalis: 12.12.2
Ammonium carbonate, For 2 M solution, 300 g in 450 mL 10% (NH3), then dilute in 1 L water
Ammonium carbonate precipitates: 12.12.4
Ammonium carbonate, smelling salts: 12.16.3.5
Ammonium carbonate solution precipitates metal carbonates:
Ammonium carbonate with ethanoic acid: 14.2.3
Ammonium carbonate decomposition: 12.12.1
Heat ammonium carbonate (smelling salts): 12.16.5
Smelling salts: 12.16.3.5
Ammonium carbonate
Ammonium carbonate (NH4)2CO3) or [NH4)2CO3.3H2O], crystal ammonia, white crystalline solid, Harmful if inhaled
Harmful if swallowed or inhaled, irritates skin, eyes, respiratory tract
Ammonium carbonate (NH4)2CO3, sal volatile, aromatic spirits of ammonia, hartshorn salt, ammonium sesquicarbonate, bakers' ammonia, crystal ammonia
It occurs as colourless crystals or white powder, ammonia-like odour, very soluble, decomposes in hot water, E503
Ammonium carbonate is double salt, ammonium hydrogen carbonate, (ammonium aminomethanoate, carbamate), (NH4HCO3.NH2COONH4)
It releases ammonia, in sal volatile, smelling salts.
Ammonium carbonate is a white powder and is fairly soluble in water to form a weak alkali.
Used as smelling salts to revive a person after fainting and to induce greater efforts from athletes and football players.
Ammonium chloride NH4Cl
Ammonium chloride
Ammonium chloride, (NH4Cl), sal ammoniac, Harmful if ingested
Ammonium chloride, (NH4Cl), For 5 M solution, 270 g in water
Ammonium chloride, Solution < 20%, Not hazardous
Ammonium chloride, (NH4Cl), salmiac, sal ammoniac, colourless, odourless, cubic crystals or crystal mass, white granular powder
It sublimes without melting, weakly hygroscopic, saline taste (soldering flux, dry cell flux in torch battery)
The mineral occurs in burning coal piles and volcanoes.
Experiments
Ammonium chloride, invisible writing ink (secret writing inks): 3.2.5.5
Ammonium chloride, Leclanché cell, dry cell, electric torch (flashlight) battery: 33.88
Ammonium chloride smoke screen: 3.6
Ammonium chloride, soldering flux: 2.33 (See: 2.)
Common ion effect in ammonium chloride solution: 17.5.5.6
Fireproof cloth: 3.5.11
Heat ammonium chloride crystals: 8.4.1
Heat-sensitive paper, cobalt (II) chloride, ammonium chloride (sal ammoniac): 5.3.10
Hydrolysis of ammonium chloride: 12.10.3.2
Hydrolysis of sodium carbonate: 12.10.3
Low cost preparation, drops of muriatic acid with ammonia solution, until red to litmus paper
Prepare ammonium chloride sunbeam mists: 7.8.2.1
Prepare nitrogen gas: 3.46
Thermal dissociation of ammonium chloride, effect of temperature: 17.5.5.5
Ammonium chlorate NH4ClO3
Ammonium chlorate, Toxic if ingested, Explosive, Not permitted in schools
Ammonium copper (II) chloride Cl4CuH8N2
Ammonium cupric chloride, H8Cl4CuN2
Ammonium copper (II) chloride, tetramine copper (II) chloride
Tetramminecopper (II) chloride, (Cu(NH3)4Cl2), ammonium cupric chloride, Harmful if ingested, skin irritant
Ammonium copper (II) sulfate hexahydrate [(NH4)2Cu(SO4)2.6H2O]
Ammonium cupric sulfate, diammonium copper (II) sulfate (VI)-6-water, [Cu(NH3)4SO4.H2O], in fire extinguishers, Environment danger
Tetraamminecopper (II) sulfate, [Cu(NH3)4(H2O)n]SO4], Tetraamminecopper (II) sulfatemonohydrate, cupraammonium (II) sulfate, dark blue solid, used in rayon production
Ammonium dichromate (NH4)2Cr2O7
Ammonium dichromate, ammonium dichromate (VI), (NOT "ammonium bichromate")
Ammonium dichromate, powder, solid, Highly toxic if ingested, Corrosive, Oxidizing (OXD 1439)
Ammonium dichromate, solid, Toxic, Corrosive, Oxidizing (OXD 1439)
Ammonium dichromate, Solution < 0.5%, Not hazardous
Decomposition of metals, metallic salts: 3.30.14
Ammonium dichromate
Ammonium dichromate [(NH4)2Cr2O7], ammonium bichromate, orange-red monoclinic crystals, decomposed by heat, may be carcinogenic.
Experiment
Heat ammonium dichromate, to form green chromium (III) oxide, nitrogen gas and water.
Start the reaction with a lighted match.
The reaction continues, because it is exothermic.
This reaction is NOT dangerous, if only small quantities of material are used.
The reaction is dangerous if particles of undecomposed ammonium dichromate are projected into the air and inhaled.
Ammonium dichromate is used in "volcano" experiments, so it is called Vesuvian Fire, but the reaction may be too dangerous for school science experiments, and ammonium dichromate may be carcinogenic.
(NH4)2Cr2O7 (s) --> Cr2O3 (s) + N2 (g) + 4 H2O (g)
ammonium dichromate --> chromium(III) oxide + nitrogen + water
Ammonium iron (III) sulfate NH4Fe(SO4)2.12H2O
Ammonium iron (III) sulfate, iron (III) ammonium sulfate, ferric ammonium sulfate (FAS), iron alum: 12.1.6
Ammonium iron (III) sulfate, diamond-shaped crystals, similar to potash alum and chrome alum, can be grown on a piece of cotton
Prepare ferric tannate with tea leaves: 9.8.2 (See 4.)
Ammonium molybdate (NH4) 6Mo7O24.4H2O
Ammonium molybdate, Irritant, Harmful if ingested: 5.4.1
Ammonium molybdate (VII) 4-water, powder, ammonium paramolybdate
Ammonium molybdate catalyst, Hydrogen peroxide with sodium thiosulfate: 17.3.1.5
Ammonium molybdate, Tests for phosphates: 12.11.5.15
Prepare ammonium molybdate solution: 5.4.1
Ammonium nitrate NH4NO3
Ammonium nitrate, Toxic if ingested, colourless crystals, soluble in water and ethanol, nitrate of ammonia garden fertilizer, in explosives
Ammonium nitrate must not be mixed with diesel oil to make an explosive mixture.
Low cost: fertilizer from garden supplies store, locate storage of small amounts away from sources of heat, fire or explosion and away from other chemicals<
Ammonium nitrate cold pack: 14.2.4
Movement of copper ions in ammonium nitrate solution: 11.2.3
Nitrates (hazards): 3.7.10
Prepare ammonium nitrate: 3.7
Ammonium oxalate C2O4(NH4)2.2H2O
Ammonium oxalate, C2H8N2O4(NH4)2(C2O4), ammonium oxalate monohydrate, ammonium ethanedioate-1-water, colourless, odourless, rhombic crystals or white granules, if heated decomposes before melting, in kidney stones, guano
For 0.1 M solution, 16 g in 1 L water, Harmful if ingested
Ammonium perchlorate NH4ClO4
Colour-white solid, powerful oxidizer, dangerous rocket propellent, Not permitted in schools
Ammonium persulfate (NH4)2S2O8
Ammonium peroxydisulfate, solutions < 25%, may be used for etching of copper and printed circuit boards.
Solid dust may damage intestinal tract and cause allergy reaction, so use safety glasses.
Ammonium persulfate, ammonium peroxydisulfate, Toxic if ingested
Ammonium persulfate, Solution < 25%, Toxic if ingested
Solid dust may damage intestinal tract and cause allergy reaction.
Use safety glasses.
Ammonium persulfate, Etchants: 7.9.20.1
Ammonium persulfate, Persulfate-iodide clock reaction: 17.2.6
Ammonium phosphate (NH4)3PO4
Ammonium phosphate, triammonium phosphate (V)-3-water, ammonium phosphate tribasic, nitrogen and phosphorus garden fertilizer, flame retardant, added to baking powders to promote yeast growth.
E342 Ammonium phosphate (emulsifier, stabilizer)
See diagram 3.1.2.6a : Matchbox.
Ammonium sulfate (NH4)2SO4
For 0.1 M solution, 13.2 g in 1 L water
Ammonium sulfate colourless, odourless, rhombic crystals or white granules, soluble in water, but not ethanol, decomposes above 280 o C, sulfate of ammonia garden fertilizer, E517, cakes when stored, mascagnite mineral.
Ammonium sulfate (NH4)2SO4), sulfate of ammonia, analytical reagent, molecular weight 132.13, Harmful if ingested
Straight fertilizers, simple fertilizers, NPKS: 9.17.1.3
Ammonia with sulfuric acid, acid-base neutralization: 12.8.1
Prepare ammonia solution
Ammonia solution (NH3) (aq) (COR 2672) (28%), 18 M
3.1.7 Nessler's reagent test for ammonia
Use eye and skin protection.
Do not mix ammonia with halogens, F, Cl, Br to avoid explosive reaction.
Ammonia with solid iodine forms a highly unstable nitrogen triiodide complex, touch powder.
Do not make touch powder!
Solution of ammonia in water, (NH3) (aq), colourless liquid, suffocating, pungent odour, absorbs (CO2) from air < 10% actual (NH3), 15.5 M, "880" ammonia solution, 0.88 gm cm -3 , aqua ammonia, ammonia water, ammonia hydrate, spirits of hartshorn, Liq. Amm. Fort. 16 mol per mL, "cloudy ammonia" contains soap solution, E527, dilute ammonia solution, 6 M, needs cool storage, alkaline solution.
Many ammonia solutions sold in supermarkets are 10% aqueous ammonia, about 5.8 M), but some contain soap.
It cannot be concentrated by distillation.
Ammonia, (NH3) (aq), or (NH4OH), For 2 M solution., dilute 330 mL of 10% solution in 1 L water
Ammonia solution (10% ammonia solution), 5.3.4
Ammonia solution 3 M: dilute 200 mL (28%), 14.8 M concentrated solution to 1 litre of water
Ammonia solution 4 M: dilute 220 mL (28%), 18 M concentrated solution to 1 litre of water ("ammonium hydroxide"),
Ammonia solution 4 M: Dilute 220 mL (28%), 18 M concentrated solution to 1 litre of water ("ammonium hydroxide"),
Ammonia solution 3 M: Dilute 200 mL (28%), 14.8 M concentrated solution to 1 litre of water,
Ammonia solution, concentrated / 35% / 0.88 g mL -1 , 18 M, 35%, 110 mL of concentrated solution for 1 litre of 2 M solution.
Ammonia [Not "ammonium hydroxide, (NH4OH)]", ammonia solution shown as (NH3) (aq), because "(NH4 + ), " ions and "(OH - ), " ions
can be detected, but "(NH4OH)" cannot be detected.]
However, an equation to show that ammonium hydroxide is a weak base with the equilibrium well to the left is as follows:
NH4OH (aq) <=--> NH4 + (aq) + OH - (aq)]
3.01 Prepare ammonia, Haber process
Ammonia is produced industrially by the Haber process with a catalyst, with direct synthesis at high pressure and temperature 45 o C.
Cloudy ammonia is clear ammonia solution with soap added in memory of the days before the Haber Process when ammonia was made from coal tar and had cloudy impurities.
It may be sold as ammonia solution 5-18 M, 10-35%, ammonium hydroxide, household and trade use.
N2 (g) + 3H2 (g) < = --> 2NH3 (g) + energy released
3.1.1 Concentrated hydrochloric acid test (hydrogen chloride test), for ammonia
Dip one end of a glass rod into concentrated ammonia solution and one end of another glass rod into concentrated hydrochloric acid.
Bring the two ends close to each other, but do not let them touch.
A blue-white smoke of ammonium chloride forms.
NH3 (g) + HCl (g) --> NH4Cl (s)
3.1.2 Odour tests for ammonia
See diagram 1.13 : Smelling test.
Ammonia solution is a weak electrolyte.
When a strong electrolyte dissolves in water, it almost completely dissociates into ions.
Weak electrolytes do not dissociate so much.
Water is a very weak electrolyte.
The properties of weak electrolytes are affected both by the properties of the molecules in the solution and the properties of the ions in the solution.
1. Note the odour of dilute aqueous ammonia solution.
Shake the solution vigorously and smell by very cautious smelling, as in the diagram.
Use very small amounts of reacting chemicals.
Do not inhale directly from a test-tube, but fan the air above the test-tube towards you.
2. Put a drop of aqueous ammonia solution in a test-tube with a stopper.
Shake the test-tube and warm it with the hands.
Note the pungent odour of ammonia.
Be careful! Do not inhale gases directly from the test-tube!
Fan the gas towards the nose with the hand and sniff cautiously.
If you detect no odour, move closer and try again.
3. Add powdered wood charcoal.
Shake the test-tube and smell the contents again.
Filter the mixture.
Heat the charcoal and note the absence of the pungent odour of ammonia.
3.1.3 Litmus tests for ammonia
Ammonia dissolves in water to form a weak base that turns moist red litmus paper blue.
1. Test for ammonia with damp red litmus paper
2. Wet red litmus paper with deionized water and stick it to the concave side of a large watch glass.
Put 1 mL of 0.1 M (NH4Cl) in a smaller watch glass or a smaller diameter beaker, heat it then add 6 M NaOH.
Cover the smaller watch glass or beaker with the inverted large watch glass.
Ammonia vapour from the smaller watch glass or beaker will turn the red litmus blue.
3.1.4 Solubility tests for ammonia
Ionization reaction, Kb = 1.8 × 10 -5
NH3 + H2O <--> NH4 + + OH -
1. Dip the open end of a test-tube containing ammonia under water.
The test-tube fills with water.
Ammonia is the most soluble of all gases.
Ammonia dissolves in water to form ammonia solution, NH3 (aq).
Do not call it "ammonium hydroxide", because while "(NH4) + " ions and "OH - " ions can be detected, "(NH4OH)" cannot be detected.
So a reaction with ammonia solution is written as follows:
X + (aq) + OH - (aq) --> XOH (s)
or as molecules:
XCl (aq) + NH3 (aq) + H2O (l) --> XOH (s) + NH4Cl (aq).
2. Show the extreme solubility of ammonia
Remove the stopper from a test-tube of ammonia and quickly put your thumb or finger over the mouth of the test-tube.
Invert the test-tube of gas in a dish of water, removing your thumb only when the mouth of the test-tube is under the water.
Describe what you see.
The solution made in this rushes up into the test-tube.
Ammonia is so soluble that it dissolves almost at once in the water at the mouth of the test-tube.
Atmospheric pressure therefore forces the water into the empty test-tube.
Ammonia has a greater solubility than hydrogen chloride.
3.1.5 Sodium bicarbonate test for ammonia
See diagram 1.13 : Smelling test.
Add solid sodium bicarbonate and heat until you can smell the ammonia given off.
3.1.6 Ammonia fountain test
See diagram 3.2.37.2 : Fountain experiment.
1. Heat the end of a delivery tube and draw it out to form a fine jet.
Fill a flask with ammonia and close the flask with a one-hole stopper with a delivery tube.
Add litmus to acidified water in a beaker.
Warm the flask gently to expand the gas and then hold the flask upside down with the lower end of the delivery tube in the acidified water.
Water soon sprays into the flask through the fine jet as the ammonia dissolves in the water and the pressure of ammonia in the flask decreases.
The litmus in the water changes from red to blue.
NH3 (g) + H2O (l) < = --> NH3 (aq) + H + + OH - (aq)
or
NH3 (g) + H2O (l) < = --> NH4 + (aq) + OH - (aq)
2. Fill a beaker with litmus solution.
Add a few drops of acid solution to the litmus in the cup until the colour just changes to red.
Fit a glass jet tube into the stopper of a flask.
Remove the stopper and jet, and start filling the dry flask with ammonia.
When the flask is full of gas, replace the stopper and jet, and quickly invert the flask with the other end of the jet tube in the litmus solution.
With the spirit burner at a safe distance, pour a finger width of methylated spirit on the flask and blow on it.
This causes the spirit to evaporate and thereby cool the flask and the gas inside it.
The contraction of the gas reduces its pressure, and atmospheric pressure forces litmus solution up the glass tube and out of the jet.
The fountain from the jet suddenly increases and the litmus changes colour.
The fountain from the jet suddenly increases for the reason given above.
The red litmus solution turns blue, because the water in the litmus solution turns part of the ammonia into the alkali ammonium hydroxide.
3. Gently heat in a bath of warm water 100 mL of concentrated ammonia solution in a 250 mL conical flask fitted with a rubber stopper and a short glass tube.
Collect the ammonia gas produced in an inverted round bottom flask, by displacement of air.
Ammonia is less dense than air.
When the round bottom flask is full of ammonia, insert a rubber stopper fitted with a short glass tube tapered inside to a narrow jet.
Immerse the external end of the glass tube in water.
Ammonia will dissolve in the water in the tube, reducing the pressure inside the flask.
Atmospheric pressure will then force water into the tube, creating a jet of water, called the ammonia fountain.
Add phenolphthalein to the water to make the reaction more spectacular.
Demonstrators and observers must wear safety glasses.
3.1.7 Nessler's reagent test for ammonia
Nessler's reagent
Nessler's reagent is not permitted in some school systems, because it contains mercury.
Add Nessler's reagent to the original solution.
A brown colour indicates the presence of ammonium ion.
The test is very sensitive, so the test solution must not contain any NH4 + added during the analysis.
3.1.8 Tests for ammonium compounds
See diagram 1.13 : Smelling test.
Add sodium hydroxide solution, then heat, and note if ammonia gas is produced.
3.2.1 Prepare hydroxides with ammonia solution
Double decomposiition experiment.
Prepare insoluble hydroxides with ammonia solution, double decomposition
Dissolve ammonia gas in water to form ammonia solution, ammonium hydroxide.
Prepare dilute solutions of alum (mainly aluminium sulfate), magnesium sulfate, and manganese sulfate.
Add ammonia solution to each prepared solution.
Note the colours of the insoluble hydroxides formed
Aluminium sulfate + ammonium hydroxide --> aluminium hydroxide (faintly white) + ammonium sulfate
Magnesium sulfate + ammonium hydroxide --> magnesium hydroxide (white) + ammonium sulfate.
Manganese sulfate + ammonium hydroxide --> manganese hydroxide (white brown) + ammonium sulfate.
These double decomposition reactions occur, because one of the products is insoluble.
3.31 Ammonia solution in a neutralization reaction
Add a finger width of dilute sodium hydrogen sulfate solution in a test-tube, add a few drops of litmus solution.
Gradually add ammonia solution to the test-tube, with shaking, using the dropping pipette, until one drop just changes the colour of the mixture to purple blue.
The ammonium hydroxide in the ammonia solution reacts with the sulfuric acid in the sodium hydrogen sulfate solution.
As ammonia solution is added, the more acid is destroyed, until a point is reached when there is no more acid and no extra ammonia has been added.
The alkali has exactly neutralized the acid (when the drop just changed the colour of the litmus), forming a salt (ammonium sulfate) and water.
Ammonium hydroxide + sulfuric acid --> ammonium sulfate + water.
3.3.2 Ammonia with copper sulfate solution
Add a finger width of ammonia solution to half a test-tube of copper sulfate solution.
A double decomposition reaction occurs as you would expect.
Note the pale blue solid formed.
Add more ammonia solution, and shake, until the solid disappears.
Try the experiment again, making the copper sulfate solution so dilute that the blue colour is scarcely visible, and adding all the ammonia at once.
The pale blue solid is copper hydroxide.
When more ammonia solution is added, it reacts with the copper hydroxide, forming a complex copper-ammonia compound, which has a deep blue colour.
This blue colour appears even with very dilute solutions of copper compounds, and so is a useful test for them.
3.3.3 Ammonia with cobalt chloride solution
To a dilute solution of cobalt chloride add a finger width of ammonia solution.
Describe what happens.
A blue-green precipitate a complex cobalt-ammonia compound forms.
3.6 Ammonium chloride smoke screen
Before starting the experiment, make sure the laboratory is well ventilated.
In one test-tube place a finger width of a mixture of sodium chloride and sodium hydrogen sulfate.
In another test-tube, placea finger width of a mixture of ammonium chloride and calcium hydroxide.
Heat both test-tubes at the same time.
Hold the mouths of the test-tubes together so that the two colourless gases can combine.
Be careful! Do not inhale the gases and fumes!
The gases are hydrogen chloride and ammonia.
The gases, hydrogen chloride and ammonia combine, forming the solid salt, ammonium chloride, tiny particles of which form the white smoke.
3.7 Prepare ammonium nitrate
1. Ammonia reacts with nitric acid to form ammonium nitrate.
However, this is a dangerous reaction.
NH3 (aq) + HNO3 (aq) --> NH4NO3 (aq)
Ammonia with nitric acid --> ammonium nitrate
2. Dissolve 138 g sodium bisulfate (sodium hydrogensulfate, swimming pool chemical) in 300 mL water.
Dissolve 85 g sodium nitrate in a minimum amount of water, then mix the two solutions.
Add ammonia solution until pH -->7.
Boil the solution until sodium sulfate crystals form in the bottom of the pan.
The decant the solution, leave to cool in a refrigerator to remove all the sodium sulfate as crystals.
Separate sodium sulfate crystals with filter paper or paper towels or coffee filters.
Heat the ammonium nitrate solution to evaporate and leave behind any sodium sulfate.
Dissolve the ammonium nitrate solution in methanol then leave to evaporate the methanol.
Sodium sulfate is not soluble in methanol.
ammonia + sodium bisulfate + sodium nitrate --> sodium sulfate + ammonium nitrate
Sodium bisulfate is used to reduce ammonia produced during animal production.
3.3.8 Tests for hydrogen chloride with ammonia solution
Hold a piece of cotton wool soaked in ammonia solution, NH3 (aq) ("ammonium hydroxide") at the mouth of a receiving test-tube.
Note the white cloud of ammonium chloride above the hydrochloric acid.
3.3.7 Tests for hydroxyl ions (hydroxide ions), ammonia solution
Be careful! The odour of ammonia indicates the presence of ammonia molecules in the solution.
Test for the presence of hydroxyl ions.
Add drops of iron (III) chloride to aqueous ammonia solution.
The reaction forms a brown precipitate that indicates the presence of hydroxyl ions in the solution.
12.1.33 Prepare hydroxides by precipitation
Put 2 cm of the following solutions into test-tubes and add dilute sodium hydroxide to each solution:
Alum (hydrated potassium aluminium sulfate),
copper sulfate,
iron (II) sulfate,
iron (III) chloride,
iron alum (iron (III) ammonium sulfate),
magnesium sulfate,
zinc sulfate.
Observe the colours of the precipitates.
The hydroxides of aluminium and zinc dissolve if more sodium hydroxide is added and the test-tube is shaken.
3.3.4 Catalytic oxidation of ammonia, with red-hot platinum wire
See diagram 13.6.6.1 : Oxidation of ammonia with platinum wire.
Be careful! Do this experiment in a fume cupboard!
Use concentrated aqueous ammonia solution in a test-tube.
Heat a spiral of platinum wire until it becomes red-hot.
Insert the wire in the test-tube above the solution.
The wire stays red hot and the reaction forms nitrogen monoxide that reacts with oxygen in the air to form nitrogen dioxide.
4NH3 (g) + 5O2 (g) --> 4NO (g) + 6H2O (g)
2NO (g) + O2 (g) --> 2NO2 (g)
3.3.5 Catalytic oxidation of ammonia, with chromium (III) oxide
See diagram 13.6.6.2 : Oxidation of ammonia with chromium (III) oxide catalyst.
Be careful! Do this experiment in a fume cupboard!
Chromium (III) oxide may be carcinogenic Use chromium (III) oxide as catalyst.
Put 0.5 g of ammonium dichromate (VI) in an evaporating dish.
Heat with an alcohol lamp until the dichromate starts to decompose.
Move the lamp away and the dichromate keeps on decomposing.
Wait until the decomposition is completed.
Heat the obtained chromium (III) oxide again to dry it thoroughly.
To make a catalyst tube, put the freshly prepared chromium (III) oxide in a dry glass tube and squeeze a little glass wool on both sides.
Be careful! Do not touch glass wool with the fingers! Do not breathe in the fibres!
Heat the catalyst tube for about 3 minutes to raise the temperature of the catalyst to above 500 o C.
Use an air pump to send slowly a stream of air through the concentrated aqueous ammonia solution in a conical flask.
Then to pass the air ammonia mixed gas over the heated catalyst.
When the catalyst becomes red hot, stop heating and continue sending the mixed gas.
Prepare the gas coming from the catalyst tube pass through a gas washing bottle of concentrated sulfuric acid.
It will remove the excess ammonia and the water produced in the reaction.
A brown-red gas appears in the collecting conical flask.
Into this flask pour a little deionized water, shake, then add a few drops of litmus makes the solution turn red to prove that nitric acid forms in this flask.
4NH3 (g) + 5O2 (g) --> 4NO (g) + 6H2O (g)
2NO (g) + O2 (g) --> 2NO2 (g)
3.3.6 Reduce copper (II) oxide to copper with ammonia
See diagram 13.6.7 : Reduce copper (II) oxide.
Pass dry ammonia over copper (II) oxide in a heated hard glass tube.
The ammonia reduces the black copper (II) oxide to brown copper and is oxidized to nitrogen gas.
2NH3 (g) + 3Cu (s) --> 3Cu (s) + 3H2O (l) + N2 (g)
3.3.1 Ammonia with copper sulfate
Put 1 cm of copper sulfate into a test-tube and add dilute ammonia solution to the tube drop by drop.
After adding each drop shake the tube.
At first a light blue precipitate forms, but as more ammonia is added the precipitate will dissolve giving a deep royal blue solution.
The colour is caused by the formation of cuprammonium sulfate, tetraamminecopper(II) sulfate, [Cu(NH3)4(H2O)n]SO4.
It is , a metal complex, related to Schweizer's reagent, tetraamminediaquacopper dihydroxide, [Cu(NH3)4(H2O)2](OH)2].
To obtain the compound in solid form add a little methylated spirit to the tube.
A violet blue precipitate forms.
If the precipitate is filtered it gives an excellent flame test for copper when introduced into a flame on the end of a wet spill or match.
It can be prepared by adding concentrated solution of ammonia to a saturated aqueous solution of copper sulfate then precipitate the product with ethanol.
The deep blue crystals may hydrolyse and release ammonia if left in the air.
3.0 Prepare ammonia gas
Prepare gases with gas generation apparatus: 13.3.0
Prepare ammonia: See diagram 3.2.37.1
See diagram 1.13a : Simple fume hood.
See diagram 3.2.37.2 : Fountain experiment.
Be careful! Prepare ammonia gas only in a fume hood or fume cupboard!
1. Put a mixture of calcium hydroxide and ammonium chloride into a test-tube to a depth of 4 cm.
Fill a U-tube with lumps of calcium oxide mixed with cotton wool.
The cotton wool is to prevent blocking of the U-tube.
Gently heat the test-tube.
The calcium oxide is to dry the ammonia gas.
Collect the less dense gas (0.769 kg / m 3 ), by downward displacement of air.
Test whether the receiver test-tube is full by holding a piece of moist red litmus paper at the opening.
Ammonia gas turns red litmus blue.
Collect test-tubes of ammonia gas and apply stoppers.
2NH4Cl (aq) + Ca(OH)2 (s) --> 2NH4OH (s) + CaCl2 (aq),
then NH4OH (s) --> NH3 (g) + H2O (l)
2NH4Cl (aq) + Ca(OH)2 (s) --> 2NH3 (g) + CaCl2 (aq) + 2H2O
2. Prepare ammonia with ammonium chloride and sodium carbonate
See diagram 1.13 : Smelling test.
Put 5 g of ammonium chloride (sal ammoniac) in 2 cm depth sodium carbonate (washing soda) solution.
Heat the test-tube.
Test for ammonia gas and with wet red litmus paper.
3. Prepare ammonia with ammonia solution and sodium hydroxide.
Add 15 g of granular sodium hydroxide to 30 mL of concentrated ammonia solution contained in a conical flask.
Immediately fix in the flask a stopper with a straight delivery tube inserted in it.
A large quantity of ammonia forms quickly.
Simultaneously, the temperature of the reaction increases and froth seethes inside the flask.
NH4Cl (aq) + NaOH (s) --> NaCl (s) + H2O (l) + NH3 (g)
4. Heat a finger width of ammonium chloride mixed with an equal amount of calcium hydroxide in a large test-tube fitted with stopper and delivery tube.
The test-tube should be inclined slightly, otherwise the water formed in the reaction can flow back into the hot end of the tube.
Collect the gas by passing it upwards into another test-tube, since ammonia is less dense than air.
A piece of moist red litmus paper, held at the mouth of the container, will show when each is full.
Insert a stopper and store the test-tubes of ammonia.
5. Mix a finger width of calcium hydroxide with an equal quantity of ammonium chloride on a sheet of paper.
Rub the mixture with the glass rod, and notice the smell of ammonia gas evolved.
Hold a piece of moistened red litmus paper over the mixture.
The litmus turns blue.
Ammonia is a gas which, when moist, has alkaline properties.
6. Prepare ammonia with sodium hydroxide and ammonium salts.
Moisten a salt spoon of ammonium chloride, carbonate, or sulfate with drops of caustic soda solution.
Ammonia gas forms.
It can be tested by smell and by the turning blue of damp red litmus paper.
7. Prepare dry ammonia gas:
Attach an U-tube packed with calcium oxide granules between the horizontal Pyrex test-tube and the vertical inverted collection test-tube.
Heat a mixture of ammonium chloride and calcium hydroxide solids in the test-tube and collect the pungent ammonia by upward delivery.
It has a very pungent odour and turns red litmus blue.
Hartshorn
Distillation of ground deer antlers forms "oil of hartshorn", or "salt of hartshorn", ammonium carbonate, used in smelling salts.
Aqueous solution of ammonia called "spirit of hartshorn".
12.1.6 Ammonium iron (III) sulfate
Ammonium iron (III) sulfate, NH4Fe(SO4)2.12H2O, iron (III) ammonium sulfate, ferric ammonium sulfate (FAS), iron alum, Toxic if ingested
Ammonium iron (III) sulfate forms violet crystals that dissolve in water to form a brown acid solution.
12.12.1 Ammonium carbonate decomposition
When heated ammonium carbonate decomposes completely into three gases or vapours, steam, ammonia, and carbon dioxide, so that the substance disappears.
Heat ammonium carbonate in a dry test-tube.
Holding the test-tube in a paper holder so that it slopes down slightly.
Observe the steam and drops of water in the cooler part of the tube.
Test for ammonia gas by smell and by holding a piece of damp red litmus paper at the mouth of the tube.
The litmus paper turns blue.
Test for carbon dioxide with lime water.
Later, none of the white powder remains at the bottom of the test-tube.
12.12.2 Ammonium carbonate with alkalis
Warm a little ammonium carbonate in a test-tube with 2 cm of washing soda solution or lime water.
Ammonia gas can again be detected by smell or by litmus.
12.12.3 Ammonium carbonate with acids
Add vinegar or citric acid to some ammonium carbonate in a test-tube.
Note the effervescence.
Test for carbon dioxide with lime water.
12.12.4 Ammonium carbonate precipitates
Add ammonium carbonate solution to solutions of copper sulfate, ferrous sulfate, magnesium sulfate, zinc sulfate, and to limewater.
Note the colours of the precipitates.
12.1.6.1 Prepare ammonium iron (III) sulfate solution
Dissolve 2 mL of the powdered crystals in two thirds of a test-tube of water.
Be careful! Do not to spill the solution on clothes, because it causes a brown stain of iron mould, followed by rotting of the cloth.
12.14.1 Prepare ammonium sulfate by neutralization
Put half a test-tube of dilute sulfuric acid into an evaporating basin and add red litmus paper.
Add dilute ammonia solution, drop by drop.
Stir the liquid with a wood splint after each addition drop.
Continue adding the ammonia solution and stirring until the litmus paper turns blue.
Remove the litmus paper and leave the evaporating basin in a hot place to evaporate or evaporate two thirds of the liquid by heating before leaving it.
White crystals of ammonium sulfate form in the dish.
12.14.2 Prepare iron (II) ammonium phosphate
Add iron powder and phosphoric acid to demineralized water and stir the mixture to form a partial solution / suspension.
Heat the mixture until no further hydrogen gas is evolved.
Add ammonia solution, ammonium hydroxide, to the mixture to form iron (II) ammonium phosphate, FeNH4PO4.
Dry the mixture to form a green-grey fine powder.
The powder can be purified by passing through a sieve and magnetic separation unit.
Iron (II) ammonium phosphate, known as ferrous ammonium phosphate, FAP, is used for iron fortification of foods and sports drinks.
12.14.3 Prepare ammonium iron (II) sulfate, Mohr's Salt
Ammonium iron (II) sulfate, Mohr's salt, (NH4)2Fe(SO4)2(H2O)6, has two cations, Fe 2+ and NH4+ .
It is a double salt of ferrous sulfate and ammonium sulfate that dissolves in water to form [Fe(H2O)6] 2+ .
Dissolve equimolar solutions of hydrated ferrous sulfate and ammonium sulfate in water with drops of sulfuric acid.
Leave to stand so it forms light green crystals of ferrous ammonium sulfate.
8.4.1 Heat ammonium chloride crystals
Heat ammonium chloride crystals
Ammonium chloride crystals decompose into ammonia and hydrogen chloride gas.
However, the crystals appear to sublime.
NH4Cl --> NH3 + HCl.
Nessler's reagent
Nesslers reagent, K2HgI4, for qualitative determination of ammonia and ammonium compounds, potassium, tetraiodomercurate-potassium hydroxide solution
Nessler's reagent is NOT permitted in some school systems, because it contains mercury.
Nessler's solution (Julius Nessler 1827-1905), is a solution of mercury (II) iodide in potassium iodide made alkaline, with sodium hydroxide or potassium hydroxide.
It may be in a caustic soda solution.
Add reagent to the original solution.
A brown colour or precipitate indicates the presence of ammonium ion.
The test is very sensitive.
A trace of ammonia give a yellow colour, but larger amounts of ammonia give a brown colour or precipitate.
The test solution must contain no NH4 + added during analysis.
12.11.3.11 Tests for ammonia, ammonium ions
Nessler's reagent
1. Tests for ammonia with damp red litmus paper
2. To test for ammonia, shake vigorously and smell.
3. Wet red litmus paper with deionized water and stick it to the concave side of a large watch glass.
Put 1 mL of 0.1 M NH4 Cl in a smaller watch glass or a small beaker, heat it then add 6 M NaOH.
Cover the small watch glass or beaker with the large watch glass.
Ammonia vapour will turn the red litmus blue.
4. Nessler's reagent is not permitted in some school systems, because it contains mercury.
Add Nessler's reagent to the original solution.
A brown colour indicates the presence of ammonium ion.
The test is very sensitive, so the test solution must not contain any NH4 + added during the analysis.
5. Note: NH 3 (aq) is preferred as there does not seem to be any detectable NH4 OH present.
Certainly there are some NH4 + ions and OH - ions.
Thus a reaction with ammonia solution is written as follows:
X + (aq) + OH - (aq) --> XOH (s)
or as molecules:
XCl (aq) + NH 3 (aq) + H2O (l) --> XOH (s) + NH4Cl (aq).
10.2.9 Tests for ammonia or amino acids or proteins with ninhydrin
Ninhydrin, C9H6O4, indantrione hydrate, (1,2,3-indantrione monohydrate), Toxic by all routes
Ninhydrin, C9H6O4, forms characteristic blue colour on heating.
Spray the paper with a spray reagent of a 2% solution of ninhydrin in ethyl alcohol in an aerosol pack.
Ninhydrin reacts with α-amino acids to yield coloured products.
Leave the filter paper in the fume cupboard, fume hood until the spray solution is dry.
Place the filter paper in an oven at 110 o C until all the spots have developed.
Circle the spots with a pencil before they fade.
Measure from the centre of each spot to the base line.
Measure the distance the solvent has travelled at each position and calculate the Rf values for each amino acid.
Find the composition of the unknown by visual comparison of spot colours and by the relationships of Rf values.