VPT 311: General and Systemic Veterinary Pharmacology (2+1)

PROCESSES INVOLVING HEATING OR DRYING

• Dessication or drying: This is the first step in the preparation of crude drugs. Formerly this was done by storing in a dry airy place. Now it is done in special ovens. Temperature should not be high enough to destroy any of the desirable unstable ingredients. Drying reduces the bulk, assists preservation or facilitates powdering.
• Desumpation: By this organic fluids are boiled until the impurities rise to the surface s scum.
• Digestion: It is prolonged maceration at higher temperature than room temperature.
• Distillation: By this volatile liquid is separated from non volatile agent by converting a liquid into vapour and condensing back to liquid.
  • Fractional distillation: means separating of a mixture of liquids having different boiling points.
  • Destructive distillation: In this substances are heated so strongly that they decompose and the volatile products which arise from decomposition are saved.
• Evaporation: This is vaporizing the solvent so that more concentration of the dissolved substance is obtained.
• Expression: This is separation of liquid from a solid by pressure.
• Fusion or Liquefaction or Melting: Melting any solid body into liquid by heat.
• Ignition: This is strongly heating a substances with full access of air sot to complete oxidation nothing but ash is left.
• Roasting or Torrefaction: By this, sufficient heat is applied to the drug so that some of the constituents are altered without affecting others.
• Scaling: By this process, layers of concentrated solutions of a drug are spread on glass and dried. The dried film is separated and broken up its scales.
• Sterilisation: By this , process bacteria and their spores are destroyed.
• Sublimation: In this, solid is vaporized by heat and the vapour is condensed as a deposit on the surface of another vessel.