Colloid and interface science deals with multi-phase systems in which one or more phases are dispersed in a continuous phase of different composition or state. Classical colloid science deals with dispersions for which at least one dimension of a dispersed phase falls within about 1 and 1000 nm. In applied colloid science the upper size limit is commonly extended to at least 10,000 to 100,000 nm. Interface science deals with dispersions in which there is an extremely large interfacial area between two of the phases. The dispersed phases may be particles, droplets, or bubbles.
Some typical systems include:
Aerosols of liquid droplets or solid particles
Foams
Emulsions
Sols or suspensions
Solid foams, emulsions or suspensions
In the early 1800s Thomas Graham noticed that some substances diffused quite quickly through parchment paper and animal membranes and formed crystals when dried. Other substances diffused only very slowly if at all through the parchment or membranes and apparently did not form crystals when dried. Graham proposed that the former group of substances, which included simple salts, be termed crystalloids, and the latter group, which included albumen and gums, be termed colloids.
Although colloidal dispersions had certainly been studied long before this time (the alchemists frequently worked with body fluids which are colloidal dispersions), Graham is generally regarded as having founded the discipline of colloid science.
The test of crystal formation later turned out to be too restrictive, the distinction of crystalloids versus colloids was dropped, and the noun colloid was eventually replaced by the adjective colloidal, indicating matter for which at least one dimension falls within a specific range of distance values.
The second property that distinguishes all colloidal dispersions is the extremely large area of the interface between the two phases compared with the mass of the dispersed phase. It follows that any chemical and physical phenomena that depend on the existence of an interface become very prominent in colloidal dispersions. Interface science thus underlies colloid science.
Now, almost 200 years after Graham's era, many specialized terms are associated with colloid and interface science.
For brief explanations of some important terms in colloid and interface science:
Glossary of Terms in Colloid & Interface ScienceFor information on a complete dictionary, see:
Dictionary of Colloid
and Interface ScienceThe Language of Colloid and Interface ScienceHome Page