Physical smoke

We have two methods to obtain smoke. One is to cool a vaporized substance in order to obtain fine particles of the same substance i.e. the original material this is a physical smoke . The other method is to obtain fine particles, which are different from the original nature of the material, by some chemical reaction, e.g. burning etc this is chemical smoke . 

To produce the physical smoke, prepare a mixture of substances A and B in the vaporized state. A must have a higher boiling point than 

To obtain the chemical smoke, produce substance A and B simultaneously by chemical reaction(burning), A becomes the smoke particles and B, which is in a gaseous state, prevents the particles of A from cohesion. In any case, the original burning materials must be in a gaseous state before the burning reaction. 

First we mention dye smoke, which is obtained by burning a mixture of some volatile dye and pyrogen. In this case the gas of the dye corresponds to the substance A and the gas which is produced by the pyrogen to B. The pyrogen must produce not only the heat necessary for vaporizing the dye, but also the gas which prevents the cohesion of the dye particles. 

When we heat the dye alone in a crucible, the vapour does not look like smoke but only like thin vapour. This vapour is observed through a microscope as in Fig.53.1. 

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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. 

Physical Smoke Chemical Smoke Whistles Salutes / Reports... 

PHYSICAL SMOKE, particles are formed by vaporization and condensation of a solid (or liquid). 

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