School Science Lessons
2025-12-19
Chemistry

Chemistry Tests

Contents
12.11.1.0 Tests for all substances
Tests for acetates: 12.11.0
Tests for acetic acid: UNBiol6
Tests for acetic acid in vinegar: 12.11.3
Tests for acetylene: 16.4.6.2
Tests for acid radicals in solution: 12.11.0
Tests for acidity of water: topic 18
Tests for adulteration with borax: 19.5.6
Tests for air in water: topic 18
Tests for air pollution: topic 18
Tests for albumin / gelatine: UNBiol6
Tests for aldehydes: UNBiol6
Tests for aldehydes with Fehling's solution: 9.5.0
Tests for alcohol, breath tests: 15.3.6
Tests for aluminium: 13.3.12
Tests for ammonia: 3.5.0
Tests for amphoterism 16.6.0
Tests for amylose / amylopectin: UNBiol6
Tests for anions: 12.11.0
Tests for antimonates, borates, oxalates: 12.11.0
Tests for antimony: 12.11.3.2
Tests for arsenates: 12.11.0
Tests for arsenic, flame tests: 12.11.3.6 (See: 2.)
Tests for ascorbic acid with dipsticks: 19.1.10
Tests for ash content of plants: UNBiol6
Tests for aspirin: 12.1.9
Tests for barium: 12.11.3.3
Tests for bicarbonates: 12.11.0
Tests for bismuth: 12.11.3.4
Tests for bismuth: 12.11.3.6, (See: 3.)
Tests for blood: 9.9.1
Tests for borates: 12.11.0
Tests for bromides: 12.11.0
Tests for cadmium: 12.11.3.6, (See: 4.)
Tests for cadmium: 12.11.3.5
Tests for calcium: 12.11.3.6
Tests for calcium: 16.5.5
Tests for carbohydrates: UNBiol6
Tests for carbon dioxide: 3.5.0
Tests for carbon monoxide topic 18
Tests for carbonates: 12.11.0
Tests for cellulose: UNBiol6
Tests for cellulose with Fehling's solution: 9.5.0
Tests for cement brick strength: 34.3.4
Tests for chlorides: 12.11.0
Tests for chlorides in water: topic 18
Tests for chlorine: 12.11.4.0
Tests for chromates: 12.11.0
Tests for chromium: 12.11.3.7
Tests for cigarette smoke: 16.5.6
Tests for cobalt: 12.11.3.8
Tests for colour of water: topic 18
Tests for concrete alkalinity: 34.2.6
Tests for conductivity: topic 18
Tests for copper: 12.4.0
Tests for dextrins in toast: 19.2.14
Tests for diastase activity: UNBiol6
Tests for dinitrogen oxide, nitrous oxide, N2O: 13.3.23
Tests for dissolved O2 in water: topic 18
Tests for ethyne: 16.4.6.2
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: UNBiol6
Tests for food: 9.3.0
Tests for gases and vapours: 12.11.2.0
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 from burning hydrocarbons: 16.4.6.0
Tests for glucose: 12.11.5.0
Tests for glycerol: 12.2.11
Tests for glycerine: 12.7.4
Tests for glycerine: 12.7.4
Tests for gypsum added to the soil: 9.15.5
Tests for haemoglobin: 9.1.14
Tests for halides, Cl, Br, I: 12.11.0
Tests for hard water: 12.4.0
Tests for hardness, lead, tin, and tin alloys: 3.62.0
Tests for harmful detergents: topic 18
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: 13.3.25
Tests for H+ ion concentration of water: topic 18
Tests for hydrogen peroxide: 17.7.23
Tests for hydrogen sulfide solution: 13.3.26
Tests for hydroxides: 12.11.0
Tests for hydroxyl ions: 3.3.7
Tests for insoluble solids in rain: topic 18
Tests for iodides: 12.11.0
Tests for ions in water: topic 18
Tests for iron: 12.11.3.9
Tests for iron in cooking water: 19.2.15
Tests for iron in water topic 18
Tests for ketones: 19.5.1
Tests for lactic acid solution: 12.7.11
Tests for lactic acid solution: 12.7.11
Tests for lead: 12.11.3.10
Tests for lemon juice effect on apple browning: 19.2.3.4
Tests for lignin: UNBiol6
Tests for limestone: 35.6.14
Tests for lipase: UNBiol6
Tests for magnesium in compounds: 12.4.12
Tests for magnesium: Mg
Tests for manganese: 12.11.3.12
Tests for melting point of lead, tin, and lead-tin alloys: 3.63
Tests for metals: 12.11.3.0
Tests for 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: 12.11.3.13
Tests for nitrates / nitrites with dipsticks: 19.5.2
Tests for nitrates: 12.11.0
Tests for nitrogen content in food: 16.5.7
Tests for nitrogen in food, soda lime test: UNBiol6
Tests for nitrous oxide: 13.3.23
Tests for organic acids / alcohols: UNBiol6
Tests for oxalates: 12.11.0
Tests for oxidase / peroxidase: UNBiol6
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 gas: 3.49.1
Tests for pectin in jelly and jam: 16.5.8
Tests for pH of environment: topic 18
Tests for pH of local water: topic 18
Tests for pH of soil: topic 18
Tests for pH of tap water: topic 18
Tests for pH with acid-base indicators: 5.6.1
Tests for phosphate ions: topic 18
Tests for phosphates: 12.11.0
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 plastics, natural fibres and synthetic fibres:3.102
Tests for plastics, thermal behaviour:4.6.0
Tests for pollution of water: topic 18
Tests for polymers: 4.0.0
Tests for potassium, sodium perchlorate: 12.11.3.14
Tests for potassium, tetraphenylborate test: 12.11.3.1.1
Tests for proteins: UNBiol6
Tests for proteins: 19.5.7
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 refuse impurity in water: topic 18
Tests for reducing sugars, Fehling's test: 9.5.0
Tests for respiration of soaked peas with limewater: 9.1.21
Tests for salinity of water: topic 18
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: 12.11.3.6 (See 8.)
Tests for silver, potassium chromate: 12.11.3.15
Tests for smell of water: topic 18
Tests for soap: 12.2.12
Tests for sodium: 12.11.3.16
Tests for sodium bicarbonate in a stomach powder: 12.1.20
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: 18
Tests for starch: 12.11.6.0
Tests for strength of mud, clay and sand bricks: 34.3.11
Tests for strength of plaster of Paris bricks: 34.3.12
Tests for strontium: 12.11.3.17
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: 12.11.3.6
Tests for sucrose with Fehling's solution: 9.5.0
Tests for sugars: UNBiol6
Tests for sugars in plant parts: 9.5.0
Tests for sulfates: 12.11.0
Tests for sulfates in water: topic 18
Tests for sulfides: 12.11.0
Tests for sulfites: 12.11.0
Tests for sulfites: 19.5.3
Tests for sulfur: UNBiol6
Tests for sulfur dioxide: 13.10.4
Tests for swimming pools: 18.5.0
Tests for synthetic fibres, burning tests: 4.3.0
Tests for tannic acid: UNBiol6
Tests for tartaric acid: 19.5.4
Tests for temperature of water: topic 18
Tests for thermometer calibration: 22.7.3
Tests for tin: 12.11.3.6 (See: 9.)
Tests for tin: 12.11.3.18
Tests for total dissolved solids: 18.5.0
Tests for toxic drugs on water flea: 16.5.9
Tests for turbidity: 18.5.0
Tests for unsaturated fats: UNBiol6
Tests for unsaturated hydrocarbons: UNBiol6
Tests for urine: 19.5.5
Tests for vitamin C, DCPIP: UNBiol6
Tests for water hardness: 12.4.0
Tests for water hardness: 18.5.0
Tests for water in plant tissues: UNBiol6
Tests for wood: UNBiol6
Tests for zinc: 12.11.3.6, (See: 10.)
Tests for zinc: 12.11.3.19
Tests for zymase / catalaset: UNBiol6

12.11.2.0 Tests for gases and vapours
Tests for acetylene: 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: 18.7.21.0
Tests for gases collected in a respirometer: 9.1.19
Tests for gases from burning hydrocarbons: 12.11.2.1
Tests for gases with hot concentrated sulfuric acid: 12.11.2.2
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

12.11.3.0 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: 12.11.3.1
Tests for antimony: 12.11.3.2
Tests for barium: 12.11.3.3
Tests for bismuth: 12.11.3.4
Tests for cadmium: 12.11.3.5
Tests for calcium: 12.11.3.6
Tests for chromium: 12.11.3.7
Tests for cobalt: < a href="#12.11.3.8H">12.11.3.8
Tests for copper: 12.4.0
Tests for iron: < a href="#12.11.3.9H">12.11.3.9
Tests for lead: < a href="#12.11.3.10H">12.11.3.10
Tests for lead ions: < a href="../topics/topicIndexL.html#15.8.3H">15.8.3
Tests for magnesium: < a href="#12.11.3.11H">12.11.3.11
Tests for manganese: < a href="#12.11.3.12H">12.11.3.12
Tests for nickel: < a href="#12.11.3.13H">12.11.3.13
Tests for potassium: < a href="#12.11.3.14H">12.11.3.14
Tests for silver: < a href="#12.11.3.15H">12.11.3.15
Tests for silver: 12.12.11.3.6, (See 8.)
Tests for sodium: < a href="#12.11.3.16H">12.11.3.16
Tests for strontium: < a href="#12.11.3.17H">12.11.3.17
Tests for tin: < a href="#12.11.3.18H">12.11.3.18
Tests for water pollution: 18.3.0
Tests for zinc: < a href="#12.11.3.19H">12.11.3.19c

12.11.4.0 Tests for chlorine
Tests for chlorine 1: 15.5.12a
Tests for chlorine 2: 12.11.4.1
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)
Tests for chlorine levels in swimming pools: 18.7.21.0.

12.11.5.0 Tests for glucose
Tests for glucose: 19.4.0
Tests for glucose and fructose with Fehling's reagent: 9.5.0
Tests for glucose and starch, "Testape": UNBiol6
Tests for glucose oxidation, blue bottle experiment: UNBiol6
Tests for glucose, Tollens' test: 9.3.10
Tests for glucose:UNBiol6
Tests for glucose and fructose with Fehling's solution: 9.5.0
Tests for glucose oxidation:UNBiol6
Tests for glucose "Testape": UNBiol6
Tests for glucose and sucrose: 12.11.5.1
Tests for glucose in apples and sweets: 12.11.5.2

12.11.6.0 Tests for starch
Tests for starch: 12.11.6.1
Tests for breakdown of starch to sugars: UNBiol6
Tests for starch, iodine solution: 1.6
Tests for starch with Fehling's solution: 9.5.0
Tests for starch, Iodine with starch: 12.19.6.10
Starches, amylum, glycogen, iodine test for starch: 16.1.15
Tests for starch hydrolysis: UNBiol6
Tests for starch in potato: UNBiol6
Tests for starch, iodine test: UNBiol6
Tests for starch with Fehling.s solution: 9.5.0

12.11.3 Tests for acetic acid in vinegar
Cool the neutralized vinegar remaining from the previous experiment under the tap.
Add to it drops of ammonium iron (III) sulfate or iron (III) chloride (ferric chloride) in solution.
The liquid turns a bright red colour.

12.11.3.2 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.

12.1.9 Tests for aspirin
Crush half an aspirin tablet and dissolve the powder by heating it with sodium carbonate, (washing soda), solution in a test-tube.
Cool the test-tube and make the liquid slightly acid by adding dilute sulfuric acid or sodium hydrogen sulfate, (sodium bisulfate), solution.
Add drops of ammonium iron (III) sulfate solution.
The liquid turns a mauve or violet colour.

12.11.3.3 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.

12.11.3.12a Tests for benzidine
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.

12.11.3.4 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.

12.11.3.5 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.

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

12.11.4.1 Tests for chlorine
See diagram 1.13a: Simple fume hood
Be careful! Prepare chlorine gas only in a fume hood or fume cupboard.
Use small quantities only.
1. Bleaching test for chlorine
Chlorine bleaches moist red or blue litmus paper, flowers and some dyes in cloth.
Use chlorine gas to bleach flower petals, leaves and hair suspended in the gas.
2. Lighted splint test for chlorine
Chlorine extinguishes a lighted splint, but hot steel wool burns in it.
3. Pass chlorine through water
Chlorine is available from chemical suppliers for school laboratory use as chlorine water.
Hypochlorous acid HClO, a bleach and a disinfectant, is a solution of chlorine (I) oxide that forms salts called hypochlorites.
Hypochlorous acid is a weak acid that easily decomposes back to chlorine gas and water.
When chlorine passes through water, a mixture of HCl and HClO forms.
The chlorine is oxidized and reduced.
Cl2 (g) + H2O (l) < = > HCl (aq) + HClO (aq)

12.11.3.7 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.

12.11.3.8 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.

12.11.2.1 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).

12.11.2.2 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.

12.11.5.1 Tests for glucose and sucrose
Glucose, C6H12O6
Copper (II) hydroxide, Cu(OH)2
Heat a glucose solution with copper (II) hydroxide solution.
A precipitate of copper (I) oxide, (Cu2O, cuprous oxide), forms that gradually turns to red.
This test reaction does not occur with sucrose.

12.11.5.2 Tests for glucose in apples and sweets
Sodium carbonate, Na2CO3
Cut four pea-size pieces of apple and put them into a test-tube with 5 mL of sodium carbonate, (washing soda), crystals.
Add 2 cm of water.
Hold the test-tube in a paper holder and heat it over a flame.
When the liquid begins to boil, continue the heating for four minutes.
A red-brown solution gradually forms that then gradually darkens until it is almost black.
Note the faint smell of burnt sugar.
This test reaction does not occur with sucrose.
Repeat the test with barley sugar and "Glucodin".

12.7.4 Tests for glycerine
Glycerol, C3H8O3
Commercial "glycerine" is about 95% glycerol.
Heat drops of glycerine in a dry test-tube with powdered sodium hydrogen sulfate, (sodium bisulfate).
Acrolein, (C3H4O, ethylene aldehyde), vapour forms with a penetrating acrid smell of burnt fat in burning cooking oil.

12.11.3.9 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.

12.7.11 Tests for lactic acid solution
Lactic acid, C3H6O3
Sodium bicarbonate, sodium hydrogencarbonate, NaHCO3
1. Add lactic acid solution to the solution to sodium hydrogen carbonate (baking soda) in a test-tube.
Note the effervescence because of the formation of carbon dioxide gas.
Test for carbon dioxide with lime water.
2. Heat lactic acid solution with iron filings.
Note the effervescence because of the formation of hydrogen gas.
Increase the reaction by adding drops of copper sulfate solution.
However, it is difficult to obtain sufficient hydrogen to test by explosion with a glowing splint.
3. Boil 5 ml of lactic acid solution with two drops of dilute sulfuric acid.
Leave the solution to cool then add it to a copper hydroxide precipitate from the reaction of copper sulfate with sodium hydroxide.
Heat the solution and observe a yellow precipitate, which turns red as copper (I) oxide (cuprous oxide) forms.

12.11.3.10 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.

12.11.3.11 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.
3. Tests for magnesium in compounds
Magnesium sulfate, MgSO4
Cobalt (II) chloride, CoCl2
Pour drops of magnesium sulfate solution on a filter paper, then drops of cobalt (II) chloride solution.
Heat the wet paper over a flame until dry and then use the flame to ignite it over a watch glass or saucer to catch any ash.
The ash has a pink colour.
The same result occurs for any solution that contains magnesium.

12.11.3.12 Tests for manganese
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].

12.11.3.13 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.

12.11.3.14 Tests for potassium
1. 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.
2. The 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.

12.11.3.15 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.

12.11.3.16 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.

12.1.20 Tests for sodium bicarbonate
Tests for sodium bicarbonate in a stomach powder
This mixture may contain calcium carbonate, magnesium carbonate, bismuth carbonate, and sodium bicarbonate, but only sodium bicarbonate is soluble.
Shake 5 mL of the powder with water in a test-tube for a few minutes.
Filter the milky liquid.
The filtrate is a colourless solution of sodium bicarbonate.
Dip the end of a wood splint into the liquid and hold it in the edge of a non-luminous Bunsen burner flame.
The flame turns an intense yellow colour, showing the presence of sodium.
Heat the rest of the solution.
Carbon dioxide forms as shown by testing with lime water.

12.11.6.1 Tests for starch
1. 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.
2. 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 dextrin, (C6H10O5)n, which is made from starch.
3. Tests for starch with iodine
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.

12.11.3.17 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.

12.11.3.1 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.

12.11.3.7 Tests for salts with flame tests
1. 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.
2. 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 on 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.

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.

12.11.3.1 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.

12.11.3.4 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 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.

12.11.3.18 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).

12.11.3.19 Tests for zinc
Rinman's green, Rinmann's green, cobalt green
Cobalt (II) nitrate hexahydrate, Co(NO3)2(H2O)6
Filter and dissolve the precipitate in concentrated nitric acid.
Add a little cobalt (II) 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