Crystallization
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Crystallization

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Crystallization Crystallization Presentation Transcript

  • CRYSTALLIZATION By: Sitwat Rafi
  • WHAT IS CRYSTALLIZATION??? Crystallization is the (natural or artificial) process of formation of solid crystals precipitation from a solution. Crystallization is a technique which chemists use to purify solid compounds. Crystallization is based on the principles of solubility: compounds (solutes) tend to be more soluble in hot liquids (solvents) than they are in cold liquids. If a saturated hot solution is allowed to cool, the solute is no longer soluble in the solvent and forms crystals of pure compound. Impurities are excluded from the growing crystals and the pure solid crystals can be separated from the dissolved impurities by filtration.
  • What Happens During a Crystallization 1 3 2 4
  • TYPES OF CRYSTALLIZATION
  • “Evaporative Crystallization” Evaporative crystallization is usually a process that is conducted under vacuum. This process is chosen when solubility of the solute is nearly independent of temperature. Special scaling problems are not a serious problem as long as boiling on the heater surface is avoided
  • OSLO CRYSTALLIZER .
  • Crystallization by cooling method Crystallization is based on the principles of solubility: compounds (solutes) tend to be more soluble in hot liquids (solvents) than they are in cold liquids. If a saturated hot solution is allowed to cool, the solute is no longer soluble in the solvent and forms crystals of pure compound. Impurities are excluded from the growing crystals and the pure solid crystals can be separated from the dissolved impurities by filtration.
  • To crystallize an impure, solid compound, add just enough hot solvent to it to completely dissolve it. The flask then contains a hot solution, in which solute molecules - both the desired compound and impurities - move freely among the hot solvent molecules. As the solution cools, the solvent can no longer hold all of the solute molecules, and they begin to leave the solution and form solid crystals. During this cooling, each solute molecule in turn approaches a growing crystal and rests on the crystal surface.
  • If the geometry of the molecule fits that of the crystal, it will be more likely to remain on the crystal than it is to go back into the solution. Therefore, each growing crystal consists of only one type ```` of molecule, the solute. After the solution has come to room temperature, it is carefully set in an ice bath to complete the crystallization process. The chilled solution is then filtered to isolate the pure crystals and the crystals are rinsed with chilled solvent.
  • SLOW COOLING
  • FAST COOLING
  • APPLICATIONS OF CRYSTALLIZATION
  • Crystallization is used in manufacture step as active pharmaceutical ingredients (APIs). Many solutes precipitate in hydrate form at low temperatures for example, the mass of water of hydration to reach a stable hydrate crystallization form is more than the available water: A single block of hydrate solute will be formed – this occurs in the case of calcium chloride It is an important application of crystallization in food industry and manufacture of sucrose from sugar. A decrease in temperature usually implies an increase of the viscosity of a solution. Too high a viscosity may give the crystallization dynamics.
  • It is used for purifying of drug. A decrease in temperature usually implies an increase of the viscosity of a solution. Too high a viscosity may give the crystallization dynamics. Polymorphism: The ability of the same molecule to crystallize in different structures, is important in the manufacture of drugs and specialty chemicals because polymorphs have different properties. Our work aims to discover polymorphs and control crystallization in polymorphic systems. Amorphous solids are preferred over crystalline solids. Organic glasses are materials for organic electronics, bio-preservation, and delivery of poorly soluble drugs.
  • Examples of natural crystallization: There are many examples of natural process that involve crystallization:  Geological time scale process examples include: • Natural (mineral) crystal formation; Rock Crystal is the name given to all clear colorless quartz. It is widely used as a popular ornamental stone and is also used as a gemstone.
  • • Snow flakes formation; Snowflakes are a particular form of water ice.
  • • Honey crystallization (nearly all types of honey crystallize).
  • Interesting facts about crystallization: • Almost any solid material can crystallize— even DNA. • One thing that is not a crystal: leaded “crystal” glass. • The oldest known pieces of our planet’s surface are 4.4-billion-year-old zircon crystals from the Jack Hills of western Australia.
  • • The center of the earth was once thought to be a single, 1,500-mile-wide iron crystal. • Tiny silicate crystals, which need high temperatures to form, have been found inside icy comets from the solar system’s distant, chilly edges.
  • Factors affecting crystallization: • Super saturation: super saturation is achieved by evaporation of solvent from the solution, cooling of solution ,production of additional solute as a result of chemical reaction, or change in solvent medium. Significant super saturation is required in the absence of seed crystal. • Time: time effect the quality of crystals produced. Rapid rate of crystallization can result in impurities being entrapped in the crystals.
  • Temperature: • Rapid cooling leads to smaller crystals while slow cooling will give larger and better crystals. Like when you try to make crystals in the refrigerator, the crystals will grow faster but in smaller pieces stuck together. But if you make crystals in room temperature, the crystals will grow slower larger.
  • • Other factors which effect crystallization are: • pH, Impurities in solution, Rate of stirring and the solvent.
  • COVALENT CRYSTALS: • Atoms in covalent crystals are covalently bonded with their neighbors, creating, in effect, one giant molecule. • Covalent solids are extendedlattice compounds, in which each atom is covalently bonded to its nearest neighbors. Because there are no de-localized electrons , covalent solids do not conduct electricity.
  • Metallic Crystals: • Individual metal atoms of metallic crystals site on lattice sites. • This leaves the outer electrons of these atoms free to float around the lattice metallic crystals tend to be very dense and have high melting point.
  • Ionic Crystals: • The atoms of ionic crystals are held together by electrostatic forces . Ionic crystals are hard and have high melting points. • Example: • Table salt (NaCl) is an example of ionic crystals.
  • Molecular Crystals: • The crystals contain recognizable molecules with in their structure . Molecular crystals is held together by non-covalent interaction like vander wall forces or hydrogen binding. Molecular crystals tend to be soft with relatively low melting point. • Example: Rock candy crystallization form of table sugar or sucrose.
  • Conclusion • Colour – A crystal’s colour will depend on the different minerals used to create it and the how the atoms within it absorb light. For example, amethyst get its hue from iron. 2. Everyday – Despite what most people think, ‘crystals’ are found all around us. As well as precious jewels, mundane materials such as salt are formed through crystallisation.
  • • 3. Quartz – Quartz is a crystal made of silica and oxygen and is one of the most common minerals on Earth. It has been used in objects like computers, watches and radios. 4. Classification – As well as being categorised by shape, crystals can be segmented based on their physical and chemical makeup into four types: covalent, metallic, molecular and ionic.
  • Thank you!