Tests for all chemical substances

School Science Lessons
2025-08-06

Tests for all substances
(UNChemTests) Contents
Tests for acetates: 12.11.1
Tests for acetic acid in vinegar: 9.3.1
Tests for acetylene (ethyne): 16.4.6.2
Tests for acid radicals in solution: 12.11.2
Tests for air pollution: 18.1.0
Tests for albumin and gelatine: 9.3.2
Tests for aldehydes, Tollens' test: 9.3.3
Tests for aldehydes with Fehling's solution: 9.5.2
Tests for alcohol, breath tests: 15.2.11
Tests for aluminium: 12.3.12
Tests for aluminium compounds: 12.3.13
Tests for aluminium compounds in solution: 12.3.14
Tests for ammonia: 3.5.0
Tests for amylose and amylopectin: 9.3.4
Tests for anions: 12.11.0
Tests for antimonates, borates, oxalates: 12.11.2a
Tests for antimony: 12.11.3.12
Tests for arsenates: 12.11.3
Tests for arsenic, flame tests: 12.11.3.8 (See: 2. Arsenic)
Tests for ascorbic acid with dipsticks: 19.1.10
Tests for ash content of plant dry matter: 9.3.5
Tests for aspirin: 5.5.6.2
Tests for barium: 12.11.3.13
Tests for bicarbonates: 12.11.4
Tests for bismuth: 12.11.3.14
Tests for bismuth: 12.11.3.8, (See: 3.)
Tests for blood: 9.9.1
Tests for borates: 12.11.5
Tests for borax / turmeric adulteration of food: 19.5.6
Tests for breakdown of starch to sugars: 9.5.1
Tests for bromides: 12.11.6
Tests for cadmium: 12.11.3.8, (See: Heat with charcoal 4.)
Tests for cadmium: 12.11.3.15
Tests for calcium: 16.5.5
Tests for calcium, flame test: 12.11.3.16
Tests for calcium carbonate (limestone): 35.6.14 (Geology)
Tests for carbohydrates, Molisch's test: 9.3.7
Tests for carbon dioxide: 3.5.0
Tests for carbonates: 12.11.7
Tests for cellulose: 9.3.8
Tests for cement brick strength (contents): 34.2.3
Tests for cement brick strength (water content): 34.2.4
Tests for cement change in weight when setting: 34.2.5
Tests for chewing gum quality by comparing bubbles: 3.4.2
Tests for chlorine: 12.11.7
Tests for chromates: 12.11.9
Tests for chromium: 12.11.3.17
Tests for cigarette smoke: 16.5.6
Tests for cobalt: 12.11.3.18
Tests for concrete alkalinity: 34.2.6
Tests for copper: 12.4.0
Tests for dextrins in toast: 19.2.14
Tests for diastase activity: 9.3.9
Tests for dinitrogen oxide, nitrous oxide, N2O: 13.3.23
Tests for dissolved oxygen, DO (Winkler method): 18.3.2
Tests for electrical inspections: 4.2.4
Tests for fabrics, Burning tests for fabrics: 4.0.0
Tests for Faraday's first law: 15.1.1.1
Tests for fats and oils: 9.3.11
Tests for food, food tests: 9.3.0
Tests for gases and vapours: 12.11.2
Tests for gases collected in a respirometer: 9.1.19
Tests for gases with hot concentrated sulfuric acid:12.11.3.6
Tests for gases and vapours: 12.11.2
Tests for gases from burning hydrocarbons: 16.4.6.0
Tests for glucose: 12.11.5
Tests for glycerol: 12.2.11
Tests for glycerine: 12.7.4
Tests for gypsum added to the soil: 9.15.5
Tests for haemoglobin, Hematrace test: 9.1.14
Tests for halides, Cl, Br, I: 12.11.10
Tests for hard water. water hardness: 12.4.0
Tests for hardness, lead, tin, and tin alloys: 3.62.0
Tests for heat: 12.11.6
Tests for household chemicals: 19.5.0
Tests for hydrogen chloride: 13.2.24
Tests for hydrogen chloride with ammonia solution: 3.3.8
Tests for hydrogen gas: 13.3.4.4
Tests for hydrogen peroxide: 17.7.23
Tests for hydrogen sulfide solution: 13.3.26
Tests for hydroxides: 12.11.11
Tests for hydroxyl ions, ammonia solution: 3.3.7
Tests for insoluble solids in rain water: 18.2.1
Tests for iodides: 12.11.12
Tests for ions in a water sample: 18.4.0
Tests for iron: 12.11.3.20
Tests for iron in cooking water: 19.2.15
Tests for ketones: 19.5.1
Tests for lactic acid solution: 12.7.11
Tests for lead: 12.11.3.21
Tests for lemon juice effect on apple browning: 19.2.3.4 (Cooking)
Tests for lignin: 9.3.12
Tests for limestone: 35.6.14 (Geology)
Tests for lipase: 9.3.13
Tests for magnesium
Tests for manganese: 12.11.3.23
Tests for melting point of lead, tin, and lead-tin alloys: 3.63
Tests for metals: 12.11.3
Tests for methane gas, burn methane: 16.5.1.2
Tests for milk: 16.0.0
Tests for moisture content of plant organs: 9.3.14
Tests for multiple reagent strips: 19.5.6, Tests with
Tests for natural fabrics, burning tests: 4.2.0
Tests for nickel, DMG: 12.11.3.24
Tests for nitrates / nitrites with dipsticks: 19.5.2
Tests for nitrates: 12.11.13, the brown ring test
Tests for nitrogen content in food, Kjeldahl method: 16.5.7
Tests for nitrogen content in food, soda lime test: 9.3.15
Tests for nitrous oxide, (dinitrogen oxide), N2O: 13.3.23
Tests for organic acids and alcohols: 9.3.16
Tests for organic functional groups
Tests for oxalates: 12.11.14
Tests for oxidase and peroxidase in plant tissues: 9.3.14a
Tests for oxidation of glucose, blue bottle experiment: 9.3.10a
Tests for oxidizing agents: 15.4.17
Tests for oxygen absorption during plant respiration: 9.1.20
Tests for oxygen content of water, (dissolved oxygen): 18.3.2
Tests for oxygen gas: 3.49.1
Tests for pectin in jelly and jam: 16.5.8
Tests for pH in the environment: 18.2.0
Tests for pH with acid-base indicators: 5.6.1
Tests for phosphates: 12.11.15
Tests for plant tissues water content: 9.3.14
Tests for plant tissues oxidase and peroxidase: 9.3.14aH
Tests for plastics, Burning tests for fabrics: 4.0.0
Tests for polymers: 4.0.0
Tests for potassium, sodium perchlorate: 12.11.3.25
Tests for potassium, tetraphenylborate test: 12.11.3.1.1
Tests for proteins: 9.4.0
Tests for proteins: 19.5.7
Tests for rain water (soluble solids): 18.2.3
Tests for reagents, multiple reagent strips: 19.5.6
Tests for reducing sugars, Benedict's test: 9.4.1
Tests for reducing sugars, Fehling's test: 9.5.0
Tests for respiration of soaked peas with limewater: 9.1.21
Tests for salt effect on buffer solutions: 12.12.11
Tests for salts with flame tests: 12.11.3.7
Tests for salts with flame test sprays: 12.11.3.9
Tests for saturated hydrocarbons, bromine water test: 9.3.33.6
Tests for silver: 12.11.3.8 (See 8.)
Tests for silver, potassium chromate: 12.11.3.26
Tests for soap: 12.2.12
Tests for sodium: 12.11.3.27
Tests for sodium bicarbonate in a stomach powder: 12.1.20
Tests for sodium chloride, flame test: 12.1.29
Tests for soils, Soil tests: 6.10.0
Tests for solubility: 12.11.3.3
Tests for soluble solids in rain water: 18.2.3
Tests for starch: 12.11.8
Tests for strength of mud, clay and sand bricks: 34.2.10
Tests for strength of plaster of Paris bricks: 34.2.11
Tests for strontium: 12.11.3.28
Tests for substances by loss on heating: 12.11.3.1
Tests for substances by sublimation, melting, decrepitation: 12.11.3.4
Tests for substances with dilute hydrochloric acid: 12.11.3.5
Tests for substances with heated charcoal and fusion mixture: 12.11.3.8
Tests for sugars: 9.3.17
Tests for sulfates: 12.11.16
Tests for sulfides: 12.11.17
Tests for sulfites: 19.5.3
Tests for sulfur dioxide: 13.10.4
Tests for sulfur in proteins: 9.3.18
Tests for swimming pools: 18.5.0
Tests for synthetic fibres, burning tests: 4.3.0
Tests for tannic acid in tea: 9.3.19
Tests for tartaric acid: 19.5.4
Tests for thermometer calibration: 22.7.3
Tests for tin: 12.11.3.8 (See: Heat with charcoal 9.)
Tests for tin: 12.11.3.29
Tests for toxic effect of drugs on water flea: 16.5.9
Tests for unsaturation: 9.6.0 Tests for unsaturation
Tests for urine: 19.5.5
Tests for vitamin C, DCPIP: 9.3.21
Tests for water pollution: 18.3.0 Tests for wheat starch for gluten: 16.6.2
Tests for wood: 9.3.22
Tests for zinc: 12.11.3.8, (See: Heat with charcoal 10.)
Tests for zinc: 12.11.3.30
Tests for zymase and catalase in yeast: 9.3.23

12.11.2 Tests for gases and vapours
Tests for acetylene, (ethyne): 16.4.6.2
Tests for ammonia: 3.5.0
Tests for carbon dioxide: 3.5.0
Tests for carbon dioxide in the breath with limewater : 9.1.18
Tests for carbon monoxide: 18.1.6
Tests for chlorine: 3.40.1
Tests for chlorine levels in swimming pools, test kit: 18.7.21.0
Tests for gases collected in a respirometer: 9.1.19
Tests for gases from burning hydrocarbons: 16.4.6.0
Tests for gases with hot concentrated sulfuric acid: 12.11.3.6
Tests for gases: Lighted splint tests
Tests for hydrogen chloride: 3.42.1.0
Tests for hydrogen gas: 3.41.1.0
Tests for hydrogen sulfide solution: 3.43.1
Tests for methane gas, burn methane: 16.5.1.2
Tests for nitrous oxide, dinitrogen oxide, N2O: 3.45.1
Tests for oxygen absorption during plant respiration: 9.6.7
Tests for oxygen gas: 3.49.1
Tests for sulfur dioxide: 13.10.4

12.11.3 Tests for metals
Tests for metal ions in water, EDTA chelates: 12.13.11
Tests for metals with borax beads: 12.11.3.1a
Tests for metals with flame tests: 12.11.3.2
Tests for antimony: 12.11.3.12
Tests for barium: 12.11.3.13
Tests for bismuth: 12.11.3.14
Tests for cadmium: 12.11.3.15
Tests for calcium: 12.11.3.16
Tests for chromium: 12.11.3.17
Tests for cobalt: < a href="#12.11.3.18H">12.11.3.18
Tests for copper: 12.4.0
Tests for iron: < a href="#12.11.3.20H">12.11.3.20
Tests for lead: < a href="#12.11.3.21H">12.11.3.21
Tests for lead, heat charcoal with mixture: < a href="#12.11.3.8H">12.11.3.8
Tests for lead ions: < a href="../topics/topicIndexL.html#15.8.3H">15.8.3
Tests for magnesium: < a href="#12.11.3.22H">12.11.3.22
Tests for manganese: < a href="#12.11.3.23H">12.11.3.23
Tests for nickel: < a href="#12.11.3.24H">12.11.3.24
Tests for potassium: < a href="#12.11.3.25H">12.11.3.25
Tests for silver: < a href="#12.11.3.26H">12.11.3.26
Tests for silver: 12.12.11.3.8, (See 8.)
Tests for sodium: < a href="#12.11.3.27H">12.11.3.27
Tests for strontium: < a href="#12.11.3.28H">12.11.3.28
Tests for tin: < a href="#12.11.3.29H">12.11.3.29
Tests for water pollution: 18.3.0
Tests for zinc: < a href="#12.11.3.30H">12.11.3.30c

12.11.5 Tests for glucose
Tests for glucose: 19.4.0
Tests for glucose and fructose with Fehling's reagent: 9.5.4
Tests for glucose and starch, "Testape": 9.5.2
Tests for glucose oxidation, blue bottle experiment: 9.3.10
Tests for glucose, Tollens' test: 9.3.10

12.11.6 Tests for heat
Heat of reaction, chromium (VI) oxide with ethanol: 14.9
Heat of reaction, potassium permanganate with ethanol: 14.8
Heat of reaction, potassium permanganate with glycerol: 14.7
Heat of reaction, potassium with diethyl ether: 14.10

12.11.7 Tests for chlorine
Tests for chlorides: 12.11.8
Tests for chlorides in groundwater: 18.3.3
Tests for chlorine 1: 15.5.12a
Tests for chlorine 2: 3.40.1
Tests for chlorine 3: 18.2.23, (Test kit for chlorine levels in swimming pools)
Tests for chlorine 4: 18.2.25, (Tests total chlorine in swimming pools)
Tests for chlorine 5: 18.2.24, (Tests for free chlorine in water, swimming pools)

12.11.8 Tests for starch
9.5.0 Tests for breakdown of starch to sugars
1.6 Tests for starch, iodine solution
9.5.3 Tests for starch with Fehling's solution
12.19.6.10 Tests for starch, Iodine with starch
16.1.15 Starches, amylum, glycogen, iodine test for starch
12.7.14 Tests for starch in adhesive paste
12.1.42 Starch with water, iodine test

12.7.14 Tests for starch in adhesive paste
Shake a drop of the paste with water in a test-tube and add a drop of iodine solution.
If the paste contains starch the contents of the test-tube turns blue-black.
If a red colour forms the paste contains a chemical called dextrin, that is made from starch.

12.1.42 Starch with water, iodine test
Shake a small pinch of powdered starch with half a test-tube of water.
The starch does not dissolve.
Tests the liquid by adding one drop of iodine solution.
No reaction is given.
Boil a small pinch of starch with half a test-tube of water for seconds.
The starch dissolves.
Cool the test-tube under the tap and add one drop of iodine solution.
A deep blue-black liquid forms.

12.11.3.1 Tests for substances by loss on heating
1. Loss of water vapour indicates the presence of water of crystallization and some basic hydroxides, basic carbonates, and acid salts.
Also, it may indicate that the substance has absorbed moisture from the atmosphere.
2. Loss of oxygen indicates oxides of silver, peroxides, sodium or potassium nitrate, permanganates and chlorates.
3. Loss of carbon dioxide indicates carbonate or bicarbonate.
4. Loss of ammonia indicates an ammonium compound.
5. Loss of nitrogen dioxide (dinitrogen tetroxide), (N2O4), indicates nitrates of heavy metals, e.g. copper, lead, zinc.
6. Loss of sulfur trioxide indicates some sulfates.
7. Loss of halogens indicates oxidation of a halide.

12.11.3.1.1 Tests for potassium, tetraphenylborate test
To 15 drops of the solution, add 5 drops of 1 M NaOH, boil the solution, add 2 drops of 6 M HCl and 15 drops of 1 M sodium acetate.
Add 3 drops of 3% sodium tetraphenylborate, NaB(C6H5)4.
If a white precipitate forms the test is positive.

12.11.3.2 Tests for metals with flame tests
Cations in an unknown solution can be identified by using flame tests.
Add drops of concentrated hydrochloric acid to the solution.
Dip a clean piece of platinum wire into it then hold it in a Bunsen burner flame.
Dip platinum wire into concentrated hydrochloric acid (12 M) then into powdered solid and heat in a non-luminous edge of a Bunsen burner flame.
When a salt is heated in the flame, it dissociates into neutral atoms and electrons are excited into a higher energy level then return to the ground state and emits light of characteristic colour for that atom.
Remember that each person observes colours differently.
The non-metal atoms in anions do emit light, but at wavelengths shorter than ultraviolet light, so we cannot see the colours.
Experiments
Check the flame test colours by doing the test for all the cations against a dark background.
Compare with the following list of colours:
Ammonium compounds: green (faint colour).
Antimony: blue-green to light blue (faint colour)
Arsenic: light blue (moistened with hydrochloric acid)
Barium: pale green to yellow-green:
Bismuth: blue
Calcium: red
Calcium compounds: brick-red to yellow (masked by barium)
Copper: blue-green
Copper compounds: green (not halides) (CuBr2 blue-green)
Lead: light blue to blue
Lithium compounds: crimson (masked by barium or sodium)
Molybdenum: yellow-green:
Phosphates: blue-green (if when moistened with sulfuric acid).
Potassium: lilac, but crimson through blue glass, violet through cobalt glass
Potassium compounds: pink-lilac to violet (not borates, phosphates, and silicates.) (masked by sodium or lithium).
Selenium: blue
Sodium: strong golden yellow, but no colour viewed through blue glass
Sodium compounds: yellow (if the yellow flame persists and is not intensified by adding 1% NaCl to the dry compound.)
Strontium: crimson
Strontium compounds: scarlet (masked by barium)
Zinc: green-white.

12.11.3.3 Tests for solubility, prepare a solution for group analysis
Dissolve 1 g of the substance in the first reagent below that can dissolve the substance.
1. Water: Try to dissolve the salt in deionized water.
If the salt does not dissolve, heat it in a test-tube to observe if the salt dissolves in hot water.
2. Dilute hydrochloric acid: If the salt does not dissolve in hot water, add dilute hydrochloric acid to observe if it dissolves.
3. Concentrated hydrochloric acid, 2.0 to 5.0 mL: When all substance is dissolved, dilute solution to five times its bulk, then leave to cool.
If the dilution produces a precipitate, because of hydrolysis of chlorides of bismuth, antimony or tin, add drops of concentrated hydrochloric acid.
4. Dilute nitric acid: It may dissolve compounds of lead, silver and mercury, but avoid using nitric acid, because it may oxidize hydrogen sulfide.
5. Aqua regia, Be careful!
Heat with concentrated hydrochloric acid, then add a few drops of concentrated nitric acid.
Dilute as in 3. above.
6. Concentrated nitric acid: Warm with 2.0 to 5.0 mL of the acid.
The solution must be evaporated to dryness and the residue dissolved in water or hydrochloric acid.
7. Insoluble residue: Filter it off, wash it, and fuse it in a crucible with four times its bulk of fusion mixture.
Cool, boil with water, filter.
Test filtrate for acid radicals.
Dissolve precipitate of metal carbonates in hydrochloric acid, and analyse separately.
If the solution so obtained gives no precipitate with that obtained by 1. to 6. above, analyse them together.

12.11.3.4 Tests for substances by sublimation, melting, decrepitation
1. Sublimation indicates the presence of ammonium halides, other halides, and some oxides.
2. Melting indicates the presence of sodium, potassium or ammonium nitrate, potassium chlorate, and other less common substances.
3. Decrepitation (crackling noise of some heated crystals), indicates the presence of sodium chloride, lead nitrate and potassium chlorate.

12.11.3.5 Tests for substances with dilute hydrochloric acid
1. Carbon dioxide produced indicates a carbonate or bicarbonate.
2. Hydrogen gas produced indicates some free metals.
3. Sulfur dioxide produced indicates sulfite or bisulfite.
4. Sulfur dioxide and sulfur produced indicates thiosulfate.
5. Hydrogen sulfide produced indicates sulfide.
6. Nitrogen dioxide (N2O4) produced indicates nitrite.
7. Chlorine produced indicates hypochlorite or oxidizing agent.

12.11.3.6 Tests for gases with hot concentrated sulfuric acid
If organic acid present, substance should be ignited, extracted with dilute hydrochloric acid and filtered before proceeding with main group separation.
Gas evolved indication
1. Hydrogen chloride produced indicates chloride.
2. Nitric acid produced indicates nitrate.
3. Oxygen produced indicates peroxide, permanganate, chromate, dichromate.
4. Chlorine peroxide (yellow green gas, violent action) produced indicates chlorate.
5. Sulfur dioxide produced indicates sulfite, thiosulfate or reducing agent.
6. Hydrogen bromide, bromine and sulfur produced indicates bromide.
7. Hydrogen iodide, iodine and hydrogen sulfide produced indicates iodide.
8. Carbon monoxide and carbon dioxide produced indicates oxalate.
9. Carbon monoxide only produced indicates formate.
10. Acetic acid produced indicates acetate.

12.11.3.7 Tests for salts with flame tests
Soak paper in the following salts, leave to dry then ignite
Calcium chloride: orange, Copper (II) chloride: blue, Copper (II) sulfate: green, Lithium chloride: red, Potassium chloride: purple, Sodium borate, borax: green.
Sodium carbonate: yellow, Sodium chloride: yellow, Strontium chloride: red.

12.11.3.8 Test substances with heated charcoal and fusion mixture
Test substances with charcoal, heat charcoal with fusion mixture, note heated metal appearance.
1. Aluminium produces a white residue.
Add drops of cobalt nitrate solution and heat again to form a blue mass, but this is also caused by fusible phosphates, arsenates, borates and silicates.
2. Arsenic produces fumes smelling of garlic and forms a white crust if seen at some distance from the flame.
3. Bismuth forms pink globules, becomes brittle and forms a yellow crust.
4. Cadmium forms a brown crust.
5. Copper forms red scales.
6. Lead forms grey-white soft globules and forms a red crust when hot and a yellow crust when cold.
7. Magnesium produces a white residue.
Add drops of cobalt nitrate solution and heat again to form a green mass.
8. Silver has shining metal particles.
9. Tin forms hard white beads.
10. Zinc forms a yellow crust when hot and a white crust when cold.
Zinc also produces a white residue.
Add drops of cobalt nitrate solution and heat again to form a green mass.

12.11.3.9 Tests for salts with flame test sprays
Be careful! Wear eye protection.
Use spray bottles, e.g. window cleaners or garden sprays, to spray saturated solutions of metal salts in ethanol onto roaring Bunsen burner flames in a darkened room.
The salts can include sodium chloride, potassium chloride, lithium chloride, and copper sulfate.
The spray bottles should have a trigger mechanism and not a scent bottle spray pump, which may allow flash back.

16.4.6.0 Tests for gases from burning hydrocarbons.
Hydrocarbons burn in excess air to form carbon dioxide and water.
The reaction is exothermic.
Methane burns with a clear flame.
Ethene (ethylene) and ethyne (acetylene) burn with a smoky luminous flame.
This flame can be seen above a chimney at many petrol refineries where excess ethene is burned off.
Experiment: Tests for gases from burning hydrocarbons
Light a natural gas burner or pour drops of cigarette lighter fuel in an evaporating basin and ignite it.
Hold a dry test-tube containing ice over the burning gas.
Water from the combustion condenses on the test-tube.
Add limewater and shake.
The milky precipitate shows the presence of carbon dioxide.
CH4 (g) + 2O2 (g) ---> CO2 (g) + 2H2O (g).
In insufficient oxygen, the poisonous gas carbon monoxide forms.
2CH4 (g) + 3O2 (g) ---> 2CO (g) + 4H2O (g).

12.11.3.12 Tests for antimony
1. Dilute with its own volume of water.
Pass H2S.
An orange-red precipitate of antimony sulfide, Sb2S3, indicates the presence of antimony.
2Sb3+ + 3S2- --> Sb2S3 (s).
2. Organic reagent: Gallocyanine (Fast violet), C15H13ClN2O5, 0.05% in M HCl.
To one drop of antimony solution on filter paper, add one drop of reagent.
A colour change from wine red to blue indicates the presence of antimony.
Use Group IIb precipitate dissolved in concentrated HCl and diluted.

12.11.3.13 Tests for barium
Confirm by flame test: Light green
Barium and strontium
Organic reagent: Rhodizonic acid, C6H2O6, [(CO)4(COH)2], 1,2-dihydroxycyclohexene-3,4,5,6-tetrone, dihydrate: C6H2O6.2H2O, 0.1% aqueous solution
Put one drop of test liquid on filter paper then add one drop of reagent.
A red-brown spot indicates the presence of Sr and Ba.
When one drop of dilute HCl is added, a barium spot is intensified and a Sr spot disappears.
Use Group V precipitate after solution in dilute acetic acid.
Prepare fresh solution of reagent if it has decolorized.

12.11.3.14 Tests for bismuth
Organic reagent: Thiourea, H2N.CS.NH2, 10% aqueous solution (10 mL Bi solution + 10 mL dilute HNO3 + 1 mL reagent)
A yellow colour indicates the presence of bismuth.

12.11.3.15 Tests for cadmium
1. Ammonium hydroxide gives white precipitate easily soluble in excess.
2. Organic reagent: Diphenyl carbazide, C13H14N4O, CO(NH.NH.C6H5)2, in saturated alcoholic solution
Add few drops of reagent to Cd to give violet coloration.
Use solution in dilute HNO3 in Group separation.
If Cu present as a blue solution, first saturate reagent with KCNS and add crystal KI, then Cu is reduced and does not interfere.

12.11.3.16 Tests for calcium
Confirm by flame test: Brick-red (green through blue glass).

12.11.3.17 Tests for chromium
1. Fuse with sodium carbonate and a little potassium nitrate in a porcelain crucible.
Dissolve in water, add acetic acid and lead acetate solution.
A yellow precipitate forms.
A filtrate may contain chromium and aluminium as sodium chromate and sodium aluminate.
A yellow precipitate indicates the presence of chromium.
Pb2+ + CrO42- --> PbCrO4 (s), [yellow lead chromate].
2. Chromium (as chromate}
Organic reagent: Diphenyl carbazide, C13H14N4O, CO(NH.NH.C6H5)2, 0.2% solution in one part glacial acetic acid and nine parts methylated spirit.
Make the chromate solution acidic with acetic acid or sulfuric acid.
Add reagent.
A deep violet-red colour indicates the presence of chromate.
Use in Group III when in form of chromate.

12.11.3.18 Tests for cobalt
Organic reagent: Nitroso-beta-naphthol, 1-nitroso-2-naphthol, C10H7NO2, 1 g in 50 mL acetic acid
Dilute to 100 mL Add reagent to neutral or slightly acid solution.
A brown colour indicates the presence of cobalt.
Use in Group IV when in solution after treatment with KClO3 and acid, or use the solution after Group III.
Cu, Fe, Sn, Ag, Cr, Bi, all interfere with the test.

12.11.3.19 Tests for copper
1. Ammonium hydroxide gives a pale blue precipitate that dissolves in excess to give a deep blue solution.
2. Organic reagent: Rubeanic acid (ethanedithioamide, dithiooxamide), NH2.CS.CS.NH2, saturated 0.5% alcoholic solution
Use 10 mL of neutral Cu solution + 1 mL 5M CH3COOH + drops of reagent.
A green-black precipitate forms.
Test with Group II precipitate.
Ni and Co may interfere with the test.
Dissolve CuS in dilute HNO3 and neutralize with NaOH solution.

12.11.3.20 Tests for iron
1. Dissolve ammonium thiocyanate in water and heat the solution.
The solution turns a characteristic red colour with iron (III) compounds, ferric compounds.
2. Organic reagent: Cupferron
NH4[C6H5N(O)NO] (ammonium salt of N-nitroso-N-phenylhydroxylamine), 5% aqueous solution
Filter if reagent is turbid.
Add reagent to strongly acidic HCl solution.
A red-brown compound indicates the presence of iron.
The reagents is unstable over long periods, but decomposition may be delayed by a piece of solid ammonium carbonate added to the reagent.

12.11.3.21 Tests for lead
Add potassium iodide solution to solutions of lead salts to form a yellow precipitate that is soluble in boiling water.
Organic reagent: Rhodizonic acid, C6H2O6, (CO)4(COH)2, dihydrate: C6H2O6.2H2O, sodium salt (CO-CO.C.ONa)2, 0.1% aqueous solution
Add two drops of reagent to a sample of Group I precipitate still wet with acid.
A violet colour indicates the presence of lead.
Make a fresh solution of the reagent, if it has decolorized.

12.11.3.22 Tests for magnesium
1. Heat on charcoal with sodium carbonate.
Add a few drops of cobalt nitrate solution and heat again to produce a pink residue.
2. Organic reagent: The complex dye Titan yellow
Na2C28H19S4O6, as 0.1% aqueous solution.
Add 2 mL 1% KOH to 2 drops of test solution.
Boil to remove NH4+ and add 2 drops of Titan yellow.
A red colour or red precipitate indicates the presence of magnesium.
Tests for Mg in a Group VI solution.
Ammonium ions interfere with the test and must be removed.

12.11.3.23 Tests for manganese
1. Fuse manganese with sodium carbonate and some potassium nitrate in a crucible to form a blue-green mass.
2Mn(OH)2 + 5O --> 2MnO4- + 2H+ + H2O, [5O from oxidizing agents], [MnO4- = purple permanganate ion].

12.11.3.23a Tests for benzidine
2. Organic reagent, C12H12N2, 0.05% solution in 10% acetic acid
To one drop of solution on filter paper add one drop 0.05% NaOH then one drop of reagent.
Use in Group IV when in solution in dilute acid.
Dissolve Group IV precipitate in very dilute acid and use the solution, rejecting any undissolved solid.

12.11.3.24 Tests for nickel
Organic reagent: Dimethylglyoxime, DMG (CH3C(NOH)C(NOH)CH3), 1% solution in methylated spirit, Toxic if ingested.
Warm a slightly acid test solution, add reagent then ammonium hydroxide until solution is alkaline.
A bright red precipitate indicates the presence of nickel.
Bismuth interferes with the test.

12.11.3.25 Tests for potassium
Reagent: Sodium perchlorate, 20% solution in equal parts of water and alcohol
Add reagent to equal volume of test solution.
A white precipitate of KClO4 indicates the presence of potassium.
Test in Group VI solution concentrated by evaporation and let cool.
Do the test on a glass plate above a black background.

12.11.3.26 Tests for silver
1. Add potassium chromate solution to neutral solution of a silver salt to form a brick-red precipitate.

2. Organic reagent: 5-(4-dimethylaminobenzylidene) rhodanine
C12H12N2OS2, 0.03% in acetone
The reagent detects AgCl in solution in water.
A red colour indicates the presence of silver.
Use a Group I precipitate.

12.11.3.27 Tests for sodium
Organic reagent: Uranyl magnesium acetate.
UO2(CH3COO)2.Mg(CH3COO)2, as a saturated aqueous solution
Add reagent to cold solution.
A yellow precipitate indicates the presence of sodium.
Test in Group VI solution concentrated by evaporation and let cool.
Do the test on a glass plate above a black background.

12.11.3.28 Tests for strontium
1. Confirm by flame test: Crimson
Sr2+ + SO42- --> SrSO4 (s).
2. Strontium and barium
Organic reagent: Rhodizonic acid (CO-CO.CONa)2, 0.1% aqueous solution
Put one drop of test liquid on filter paper then add one drop of reagent.
A red-brown spot indicates the presence of Sr and Ba.
When one drop of dilute HCl is added, a barium spot is intensified and a Sr spot disappears.
Use Group V precipitate after solution in dilute acetic acid.
Prepare fresh solution of reagent if it has decolorized.

12.11.3.29 Tests for tin
1. Use a borax bead containing some copper (II) sulfate.
Add a sample of the original solid and heat again to produce a red bead.
2. Organic reagent: Cacotheline
C21H21O7N3, saturated solution in water
Tin must be as Sn (II) in M HCl.
Add drops of reagent.
A violet colour indicates the presence of tin.
Stability of reagent is about 14 days.
Cu, Ni, Co, Cr and Fe interfere with the reaction.
Do the test with Group IIb solution when as Sn (II).

12.11.3.30 Tests for zinc
Filter and dissolve the precipitate in concentrated nitric acid.
Add a little cobalt nitrate solution, evaporate to concentrate, and soak a filter paper in the mixture.
Ignite the filter paper.
A green ash (Rimann's green) indicates the presence of zinc.
The green ash is a compound of zinc and cobalt oxides.
2ZnO22- + 8H+ + 2S2- --> 2ZnS (s) + 4H2O.