Separation Methods PDF

Ministry of Higher Education &Scientific Research College of Sciences /Kirkuk University Department of Chemistry Level 2 Separation methods Product By: Dr. Tamara Negirs Ahmed  Chemical separation techniques Chemical se...

Ministry of Higher Education &Scientific Research College of Sciences /Kirkuk University Department of Chemistry Level 2 Separation methods Product By: Dr. Tamara Negirs Ahmed  Chemical separation techniques Chemical separation techniques are considered important analytical methods used to obtain different materials in a pure form, free from impurities, and to identify the nature of those materials. In many cases, the separation process is essential when it is necessary to perform other tests on the pure material, such as spectral tests (IR, NMR, and mass spectrometry). Obtaining the pure material also facilitates conducting quantitative analyses to determine its concentration. In other words, chemical separation methods are crucial in both descriptive and quantitative analysis. They are used to prevent interference during chemical analysis. Separation techniques rely on differences in at least one of the physical or chemical properties of the materials to be separated, such as solubility, fractional dissolution, adsorption, boiling and melting points, ion exchange, and particle size. The greater the difference in one of these properties, the easier the separation process becomes. The following table includes the classification of separation techniques according to physical and chemical properties Distillation Distillation is the process in which a substance is converted from a liquid state to a vapor state, then the vapor is condensed by cooling it in a condenser, turning it back into a liquid. This results in a pure liquid. Essentially, distillation involves heating the liquid to the temperature at which it turns into vapor, then condensing the vapor to return it to a liquid state, and collecting it in another part of the apparatus. In other words, two processes occur simultaneously—evaporation and condensation. Evaporation happens when the liquid is heated, and condensation occurs in a part of the apparatus called the condenser. Types of Distillation: 1. Simple Distillation: This type of distillation is commonly used in the following cases: 1. Purification liquids from non-volatile solids. 2. Separating two or more liquids based on the difference in their boiling points when the difference is greater than 50°C. 3. Measuring the actual boiling point of liquids. How Distillation Occurs: - When a substance is heated in a distillation flask with a small flame, the vapor pressure of the liquid (which is the ability of the molecules to escape from the surface of the liquid) will increase until it equals the external pressure. - With continued heating, sufficient heat is provided to convert the liquid into vapor, causing the vapors to rise through the neck of the flask, then condense and return to the distillation flask. - When the neck of the flask is heated, the vapors exit through the side opening of the distillation flask and then pass through the condenser to the container collecting the substance. Distillation continues at a rate of a drop or two per second. (Figure 1):The figure shows simple distillation