Physico 1 PDF

9. Trituration  Trituration may be used both to comminute and to mix powders. By trituration the grinding of a solid substance is done to fine powder by continuous striking or rubbing the particles in a mortar with a pestle. If simple admixture is required without special need for comminut...

9. Trituration  Trituration may be used both to comminute and to mix powders. By trituration the grinding of a solid substance is done to fine powder by continuous striking or rubbing the particles in a mortar with a pestle. If simple admixture is required without special need for comminution, the glass mortar is usually preferred. When a small amount of a potent substance is to be mixed with a large amount of diluent, geometric dilution method is used to ensure the uniform distribution of the potent drug. Applications 1. Size reduction. 2. Geometric mixing of powders 10. Efflorescence  Efflorescence is the loss of water of crystallization from a hydrated salt to the atmosphere on exposure to air. The hydrated substances under normal conditions exert vapour pressure due to their water of crystallization. HYDRATES: Solids that contain water molecules as part of their crystalline structure. The water in the hydrate is known as the water of hydration or the water of crystallization. The combination of water molecules with molecules of a compound results in a hydrate  A large number of compounds crystallize in hydrated form. e.g., CuSO4 combines with 5 molecules of water. Na2SO4 combines with 10 molecules of water. MgSO4 combines with 7 molecules of water. FeSO4 combines with 7 molecules of water. Presence of water of crystallization is not essential for crystal structure, as Sodium chloride, potassium nitrate and many other compounds have definite crystal structures without water of crystallization Application 11. Exsiccation üExsiccation is the process of removing the water of crystallization from the hydrated crystalline substances by heating and making them less hydrous or anhydrous üThe examples of exsiccated substances include; exsiccated ferrous sulphate, exsiccated magnesium sulphate, exsiccated sodium sulphate, exsiccated sodium carbonate, exsiccated alum and anhydrous sodium arsenate üIn the laboratory, exsiccation may be carried out by taking a weighed amount of the substance in a tared dish which is heated on a water bath, sand bath or in an oven, with continuous stirring until a constant weight is obtained or until the calculated loss in weight has taken place Application 1. Exsiccation is carried out to get an anhydrous product required in the formulation of pharmaceuticals.. 2. After the removal of water the bulk and weight of the drug is reduced and they can be easily administered/used in manufacturing. 3. Potency of drug is increased after the removal of water. 4. After exsiccation fine powder is obtained which is easy to handle. 12. Adsorption  Adsorption is accumulation of molecules on a surface (a surface layer of molecules) in contact with an air or water Adsorbate is a material being adsorbed Adsorbent is the material doing the adsorbing. Egs. Activated carbon or ion exchange resin Factors such as thickness of adsorbed layer of gas, reversible character, adsorption and surface area, nature of gas, heats of adsorption, effects of pressure and temperature affects rate of adsorption. How does these factors affect adsorption Application of adsorption 1. Production of high vacuum If a partially evacuated vessel is connected to a container of activated charcoal cooled with liquid air, the charcoal adsorbs all the gas molecules in the vessel. This result in high vacuum 2. Gas mask Gas masks are devices containing an adsorbent (activated charcoal) or a series of adsorbents; these adsorbents remove poisonous gases by adsorption and purify the air for breathing 3. Removal of coloring matter from solution Animal charcoal removes colours of solution by adsorbing coloured impurities, thus in the manufacture of cane-sugar, the coloured solution is clarified by treating with animal charcoal or activated charcoal 4. Chromatographic analysis Mixture of small quantities of organic substances can be separated with the help of chromatography which involves the principles of selective adsorption 5. Heterogenous catalysis In a heterogenous catalysis, the molecules of the reactant are adsorbed at the catalyst surface, where they form an adsorption complex. This decomposes to form the product molecules which then take off from the surface 13. Deliquescence  HYGROSCOPIC: A substance is hygroscopic if it readily absorbs water from the atmosphere and forms a hydrate. DELIQUESCENT: A substance is deliquescent if it absorbs water from the air/atmosphere until it forms a solution. Both these terms are used to indicate that a material takes up water vapors from the atmosphere and is converted to a more hydrated form. In case of hygroscopic substance, the more hydrated state is till a solid but in deliquescence there is eventual formation of a liquid phase i.e., a solution. Such substances are said to be DELIQUESCENT, and the process is termed DELIQUESCENCE. Very soluble salts, such as CaCl2 are often extremely deliquescent.  Deliquescent salts include calcium chloride, magnesium chloride, zinc chloride, potassium carbonate, potassium phosphate, potassium hydroxide, and sodium hydroxide. Examples of hygroscopic materials include, exsiccated sodium sulphate, ammonium chloride etc. For Hygroscopic and deliquescent pharmaceutical preparations specialized storage conditions are required. Applications : Owing to their very high affinity for water, these substances are often used as desiccants; these compounds are used in the chemical industry to remove the water produced by chemical reactions.