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Purification of Impure Samples by Crystallization Theory Our Objective Our Objective is to prepare the crystals of the following substances form their impure samples through crystallisation Copper sulphate Potash alum Benzoic acid  The Theory What happens during crystallisation? The chemicals used for various purposes should be pure, completely free from any type of impurities. Method of purification of a substance depends upon the nature of impurities present in it. There are various methods for the purification of substances, e.g., filtration, evaporation, decantation, distillation, and crystallization. Crystallisation is one of the very important purification techniques, purifying substances by removing unwanted by-products. Crystalline compounds are generally purified via this crystallisation process. The principle behind the crystallisation is that the amount of solute that can be dissolved by a solvent increases with temperature. In crystallisation, the imp

Qualitative Analysis of Organic Compounds (Sodium fusion Test or Lassaigne Test) Objective: 1. To carry out Lassaigne test in order to determine the elements (N,S halogens) present in the unknowns. 2. To identify the elements present in compounds and their colouration. Introduction: Qualitative analysis is always applied as a first step in identifying a compound when a new compound is readily prepared or isolated from some natural source. In an organic compound, elements carbon, hydrogen and oxygen are assumed to be present commonly. Nitrogen, sulphur and halogens (chlorine, bromine and iodine) may also present in the organic compound. The identification of elements in a given compound is a type of qualitative analysis since the experiment is dealing with the composition of a unknown compound. This experiment must be handled very carefully as further the analysis of the organic compound is according to the element present in it. Generally, the tradition

Qualitative Analysis of Elements The most commonly occurring elements in organic compounds are carbon, hydrogen, oxygen, nitrogen, sulphur and halogen elements. There is no direct method for the detection of oxygen. For detecting nitrogen, sulphur and halogens, we can use the sodium fusion test (Lassaigne’s test). Sodium Fusion Test This test is used for the qualitative analysis of elements nitrogen, sulphur and halogen in Organic compounds. In order to detect them, it is necessary to convert them into ionisable inorganic substances. 1) Test for Nitrogen We can detect cyanide ion and hence, nitrogen ion in the sample by the Prussian blue test. The filtered alkaline solution resulting from the action of water upon the sodium fusion is treated iron (II) sulphate and thus, forms sodium hexacyanoferrate (II). Upon boiling the alkaline iron (II) salt solution, some iron (III) ions are insensibly produced by the action of air. Now, we add dilute sulphuric acid to dissolve th