types of disperse systems

  1. Definitions

    Materials may be mixed together to form a true solution, a coloidal dispersion, or a coarse dispersion.

    • A true solution - mixture of two more more components that form a homogenous molecular dispersion, i.e. a one-phase system, the composition of which can vary over a wide range.
    • A colloidal dispersion - represents a system havin a particle size intermediate between that of a true solution and a coarse dispersion, roughly 10Å to 5000Å (0.1mm = 1000Å)
    • A coarse dispersion the diameter of the particles in emulsions and suspensions for the most part being larger than 0.1mm(1000Å).
    Disperse Phase Dispersion Medium Solution Collodial Dispersion Coarse Dispersion

    Dispersed Phase

    < 1nm

    Dispersed Phase

    1nm to 1mcu

    Dispersed Phase

    > 1 mcu (1 micron)

    Gas Gas Air n/a n/a
    Liquid Gas Water Vapour Fog Spray
    Solid Gas Sublimed Idoine Smoke Dust
    Gas Liquid Carbonated Water Foam Foam
    Liquid Liquid Alcohol in Water Liquid surfactant micelles Emulsions
    Solid Liquid NaCl in Water Polymer or protein solutions Suspensions
    Gas Solid Hydrogen in palladium Solid Foam Solid Foam
    Liquid Solid Mineral oil in paraffin   Solid Emulsion
    Solid Solid "Solid dispersion" Colloidal Gold in glass "Solid suspensions"
  2. Conventions

    1. General

    • In a binary (two component) solution, the component present in the greatest concentration is referred to as the solvent.The compound present in the lesser amount is referred to as the solute.

    2. Specific

    • When a solid is dissolved in a liquid, the liquid is referred to as the solvent regardless of concentration.
    • In a solution of liquids, water it present is considered to be the solvent.
    • In mixture of liquids which are miscible in all proportions. the terms Solute a solvent have little relevance.

    3. Concentration terms

    Molarity (M) Moles (gram molecular weights) per litre of solution
    Normality (N) Gram equivalent weights per litre of solution
    Molality (m) Moles of solute in 1000 g of solvent
    Mole fraction Moles solute / [Moles solute + Moles solvent]
    Mole percent Mole fraction x 100
    Percent by weight (%w/w) Grams of solute per 100 g solution
    Percent by volume (%v/v) mL solute per 100 mL solution
    Percent weight in volume (%w/v) Grams of solute per 100mL solution
    Milligram percent Milligrams of solute per 100mL solution
  3. Electrical Properties of Solutes

    The solutes (whether gases, liquids, or solids) are divided into two main classes; nonelectrolytes and electrolytes.

    • Non-electrolytes
      Non-electrolytes are substances that do not yield ions when dissolved in water and therefore do not conduct an electic current through the solution, i.e. sucrose, glycerin, naphthalene, and urea. Colligative properties of solutions of nonelectrolytes are fairly regular. A 0.1 molar solution of non-electrolyte produces approximately the same colligative effect as any other nonelectrolytic solution of equal concentration.
    • Electrolytes
      Electrolytes are substances that form ions in solution, conduct the electric current and show apparent irregular colligative properties, i.e. produce a considerably greater freezing point depression and boiling point elevation than do nonelectrolytes of the same concentration, i.e. hydrochloric acid, sodium sulfate, ephedrine, and phenobarbital.
      Electrolytes may be subdivided into strong electrolytes and weak electrolytes depending on whether the substance is completely or only partly ionized in water.
      • Strong electrolytes: Dissociate completely in water. Eg, Sodium chloride, hydrochloric acid, sodium sulfate;
      • Weak electrolytes: partially dissociate and is an equilibrium process. Eg, ephedrine, phenobarbital.