How an Aerosol Can Works
At one time or another, most of us have probably used an aerosol can. With just a push of the button, we easily and quickly apply just the right amount of furniture polish, bathtub cleanser, or underarm deodorant. It is obvious to us that the aerosol can is more convenient than the old-fashioned jars of liquid polish or cans of powdered cleanser, which can spill or be applied too thickly. At the same time, however, most of us probably do not know how the aerosol can works. We accept its ease and convenience without realizing that the aerosol can is quite a complex container.
An aerosol is not a simple cleaner or polish; it is a colloidal system. That means it consists of finely divided liquid or solid particles, called a product, dispersed in and surrounded by a gas. The most commonly used gases, or propellants, are chlorinated hydrocarbons, butane, propane, isobutane, vinyl chloride, and nitrogen. Nitrogen is used particularly for products when the taste or smell of the propellant is not desired in the product, for example, in toothpaste or whipped cream.
To complicate things further, the propellant, or gas, is present in either a liquid or a gaseous state. If the propellant is liquid, it is mixed with the product in the form of a solution. An example of this type of aerosol is hair spray. The spray or lacquer is usually dissolved in alcohol and then completely mixed with the propellant. If the propellant is present in a gaseous state, the container usually is about half-filled with the product and half-filled with a propellant such as nitrogen. The propellant gas...