Factors Affecting Solubility

• Very Soluble


  Less than 1
• Solubility

  • In the USP/NF is expressed as the number of milliliters of a solvent that will dissolve one g of a solid.
  • Parts of solvent needed to dissolve 1 part solute
• Freely Soluble


  1 – 10
• Soluble


  10 – 30
• Sparingly Soluble

  30 – 100
• Slightly Soluble

  100 – 1,000
• Very Slightly Soluble

  1,000 – 10,000
• Practically Insoluble

  Greater than 10,000
• Nature of Solute and Solvent


  “like dissolves like”
• Temperature


  The higher the temperature, the greater the solubility of solid
• Exothermic dissolution


  Solubility increases with decrease in temperature
• Endothermic dissolution


  Solubility increases with increase in temperature
• The higher the temperature, the lesser the solubility of gas.
• Pressure


  Pressure does not affect solubility of solid, but pressure affects solubility gas. The higher the pressure, the greater the solubility of gas.
• Particle Size/Surface Area


  Decrease Particle Size = Increase Surface Area = Increase Solubility
• Agitation


  Agitation increases solubility
• Non-polar

  • When molecules are made of one type of atom.
  • Noble gases
  • If the molecule has a complete symmetry
  • Electronegativity Difference (this is not accurate)
• Polar

  • “Unequally distributed electrons”
  • If Hydrogen is directly attached to N, O, F
  • If it lacks symmetry