Science made alive: Chemistry/Experiments

Experiments, lexicographically ordered

	element	required compound	link to experiment
	S	KIO₄ S	Pyrotechnic mix with purple gaseous combustion product. Potassium periodate, mixed with sulphur gives a mix, which burns without smoke, but produces a nice purple gas mix of iodine and sulphur dioxide.
*	S	KIO₄ NH₄SCN	Colored smoke -- purple and yellow. A mix of potassium periodate and ammonium thiocyanate is ignited. This gives purple smoke, which quickly turns yellow. Quite a remarkable experiment.
*	S	S₈ C₆H₅CH₃	Recrystallization and/or refining of sulphur. Sulphur is dissolved in hot toluene and when this solution cools down, nice crystals of sulphur are formed.
*	S, C, N	N₂O CS₂	Barking dog reaction . Nitrous oxide is mixed with carbon disulfide vapor and this mix is ignited. This results in a very spectacular reaction with bright light and an impressive barking noise in which yellow elemental sulphur is deposited.
	S	SOCl₂ H₂SO₄ (concentrated) K₂Cr₂O₇	Thionyl chloride and potassium dichromate, no reduction of dichromate without water. Potassium dichromate is dissolved in thionyl chloride. It is not reduced to chromium(III). With concentrated sulphuric acid and water, chromyl chloride and HCl are formed.
*	S, Cu	CuSO₄·5H₂O Na₂SO₃ Na₂S₂O₅ H₂SO₃ NaOH	Redox chemistry and coordination chemistry of copper(II) and sulfite at different pH. Sulfite ion and copper(II) ion can react in different ways. Coordination complexes can be formed, but they also can interact in a redox reaction. Quite remarkable compounds can be formed in these reactions. The pH of the solutions has great influence on the actual reactions occurring.
*	Se	Se Na₂S.xH2O H₂SO₄ (dilute) NaOH Na₂S₂O₈ Na₂SeO₃ SeO₂ HBr (40%, 48%) Na₂SO₃	Less common aspects of selenium chemistry . The element selenium has some interesting properties in combination with sulfide and bromide. It can form strongly colored species, which are stable in aqueous solution and can be studied without the need of exotic solvents.
*	Se	Se HNO₃ (≥ 50 %) Zn Na₂SO₃ (or Na₂S₂O₅)	Allotropes of selenium. Gray selenium is dissolved in conc. nitric acid, giving selenous acid in solution. This solution in turn is reduced to selenium. The selenium now precipitates as the red allotrope.
*	Te, Se, S	Te Se S NaH₂PO₂·H₂O Na₂S·xH₂O K₂Cr₂O₇ H₂SO₄ (concentrated) H₂O₂ (3%) P₄O₁₀ (optional) SO₃ (20% oleum)	Poly cation species of tellurium and selenium, no similar reaction with sulphur under the same conditions. Tellurium and selenium are dissolved in hot concentrated sulphuric acid. The solutions contain remarkable cationic species with peculiar structure. Sulphur does not show such a reaction in sulphuric acid, but it does react with oleum.
*	Te Cl, Br, I	TeO₂ Na₂TeO₃ HCl (30% by weight) HBr (40% by weight) H₂SO₄ (dilute) KI Na₂SO₃	Colorful properties of halogen complexes of tellurium in oxidation state +4. At very low pH, tellurium in oxidation state +4 forms remarkable compounds with the halide ions. The heavier the halogen, the more stable the complex and the more intense the color. All of these complexes, however, are very prone to hydrolysis in aqueous solution.

back to main experiments page