Colour change in smoke

The colour change in the smoke is caused by the following phenomena ... 

In the majority of coloured smokes, even with some physical smokes, colour change generally occurs during the generation of the smoke. A clear beautiful colour changes gradually to a whitish or yellowish one, or suddenly a flame appears and burns out the smoke particles to make them invisible. 

From early times it has been used for black smoke in combination with potassium chlorate. The composition cannot be stored for a long time, because the naphthalene sublimes, but the black colour of the smoke is so clear, that it is quite popular in use even at present. Care must be taken because there is often a risk of changing the ratio of the components spontaneously to form a dangerous composition due to the sublimation of the naphthalene. 

What to look for. Colour of flame, visible changes in film sample, smoke formations. 

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