Sciencedoze: Science, Education and Technology

What is Crystalline Melting Point ? When a polymer is treated beyond its glass transition temperature (T𝘨), it passes from a glassy state to a rubbery state and further heating causes melting of the polymer and starts flowing.  So we can say that the temperature below which the polymer is in a rubbery state and above which it is a liquid is called the crystalline melting point (T𝘮) of the polymer. Factors affecting crystalline melting point (T𝘮) Following are the factors which affect the crystalline melting point (T𝘮). 1. Chain Flexibility Chain flexibility and crystalline melting point (T𝘮) are inversely proportional to each other that is higher the flexibility, the lower will be the Tm . Also, the presence of double bond and aromatic group in the polymeric backbone lowers the flexibility which increases the crystalline melting point (T𝘮). 2. Size and type of side groups Size and type of size groups greatly influence the crystalline melting point (T𝘮). Bulky or large side g

What is Atomic Absorption Spectroscopy? Atomic absorption spectroscopy provides us the data about the absorbance of electromagnetic radiation by specific elements. This technique is widely used to determine the presence of unknown elements like alkali and alkali earth metals in the sample.  This is supported by the fact that different metals will absorb different wavelengths of radiation and transmitted radiation is detected by using Lambert Beer's law the graph between the absorbance and the wavelength of the radiation is plotted. Instrumentation of Atomic Absorption Spectroscopy 1. Radiation source The most common radiation source in Atomic Absorption Spectroscopy is a hollow cathode lamp (HCL). It contains a tungsten anode and a cylindrical hollow cathode made of the element of desire which is the element that is to be determined in the sample.  These anode and cathode are sealed into a glass tube filled with an inert gas like neon or argon . When a voltage is applied betwee

What is flame emission spectroscopy? Flame emission spectroscopy provides us atomic emission spectrum based on the excitation of atoms from a lower energy state to a higher state. When these atoms return to their original state, they emit radiations which are used to draw the graph.  This technique is widely used to determine the presence of unknown elements like alkali and alkali earth metals in the sample. This is supported by the fact that different metals have different band gaps and they will show different emission spectrums. Instrumentation of flame emission spectroscopy 1. Sample The sample is kept in a sample chamber which is connected to a tube with a nebulizer. The sample may be liquid or solid. The solid sample is first dissolved in a solvent and then analyzed. The sample cannot be a gas. 2. Nebulizer The nebulizer is a closed chamber connected with the sample through a tube. It also has a continuous supply of fuel and oxidants for the smooth flow of the flame. The nebuliz