What is an aerosol spray

Squirting a solution of perfume through a fine tube, near the end of which is a slight constriction, generates a fine spray of perfume comprising tiny particles of liquid. The spray remains airborne for a short time, and then settles under the influence of 

A colloid is a broad category of mixtures, and is defined as one phase suspended in another. A perfume spray is made up of a liquid (the perfume) dispersed in a gas (the air). The principle underlying the perfume atomizer is the same as the nozzle on a can of polish, and the jets within the carburettor in the internal combustion engine. In each case, the colloid formed is an aerosol. 

The word colloid comes from the Greek root coll, meaning glue.  

Emulsion paint is easy to apply, aesthetically good looking, and forms a hard wearing and waterproof coating. Like milk in the previous example, the paint comprises one phase dispersed within another. It is a colloid, but this time a liquid finely dispersed in another liquid, which we call an emulsion. 

In emulsion paint, the dispersion phase is the liquid of the paint and is generally water-based for emulsion paints. The water is buffered (p. 269) with ammonia or simple amines to yield a slightly alkaline solution. The dispersed phase in most emulsion paints comprises small particles of immiscible urethane. 

---