Sulphur dioxide turns acidified potassium dichromate solution 

1. Practical Chemistry

Practical chemistry deals with the qualitative analysis of compounds.

2. Wet and dry test analysis:

(i) Qualitative analysis can be divided into two types: dry test analysis and wet test analysis.

(ii) In dry test analysis the salts are heated strongly in a dry, glass test tube and characteristic odour of the gas released is used to identify the negative radicals present in the compound. For example, release of ammonia gas.

(iii) A flame test is an analytical procedure used in chemistry to detect the presence of certain elements, primarily metal ions, based on each element's characteristic emission spectrum. For example, golden-yellow flame ${\mathrm{Na}}^{+}$ for blue-green flame for ${\mathrm{Cu}}^{2+}$, etc.

(iv) Wet test refers to chemistry generally done in liquid phase.It is used for identification of cations by the action of strong and weak alkalis or for the identification of anions by the action of concentrated sulphuric acid.

3. Tests of some compounds:

(i) Test for Hydrogen : Burns with a pop sound when a burning splint is brought near it.

(ii) Test for carbon dioxide : When carbon dioxide is passed over lime water, it turns milky.

(iii) Test for sulphur dioxide: Potassium permanganate solution pink colour changes to clear and colourless when passed.

(iv) Ammonium salt when heated with alkali (except ammonium hydroxide) produces ammonia gas having its characteristic smell.

(v) Carbonate and bicarbonate on heating evolves carbon dioxide.

(vi) Hydrated salts on heating produces water vapour.

(vii) Sulphites and some sulphates when heated produce sulphur dioxide gas

(viii) Copper compounds decompose to give black copper oxide.

(ix) Some naturally occurring acids are acetic acid, formic acid, citric acid, etc.