Thorough and careful studies have shown that when a solid or a liquid is introduced into another liquid, and becomes dispersed or distributed through it, the mixture may be either a true solution, a colloidal solution, or a mechanical suspension. The characteristic differences between these three conditions may be tabulated as follows: although the significance of some of the phrases used will not be apparent until the phenomena in question have been considered in some detail. -----------------------+------------------------+------------------------ True Solutions. | Colloidal Solutions. | Suspensions. -----------------------+------------------------+------------------------ | | (_a_) Particles of the | | disperse phase are: | | | | In molecular | In colloidal | In mechanical subdivision | subdivision | subdivision | | Invisible | Visible under | Visible under | "ultrascope" | microscope or to naked | | eye | | Less than 1µµ | 1µµ to 1µ in diameter | Greater than 1µ in in diameter[6] | | diameter | | Pass through filters | Pass through filters | Do not pass through and parchment membranes | but not through | filters or parchment | parchment | | | In molecular motion | In Brownian movement | In gravitational | | movement | | (_b_) The system | | exhibits: | | | | High osmotic pressure | Low osmotic pressure | No osmotic pressure | | Transparency | "Tyndall phenomenon" | Is generally opaque | | No gel-formation | Forms gels | No gel-formation | | -----------------------+------------------------+------------------------ FOOTNOTES: [6] 1µ is one-thousandth of a millimeter; 1µµ is one-thousandth of a µ, or one millionth of a millimeter.