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21) How do you detect nitrogen, sulphur and halogen using sodium fusion extract, (SFE), , (Lassaigne’s test)?, , , , Elements | Experiment Observation, , , , Nitrogen | SFE + freshly prepared FeSO, solution, | Prussian blue ppt/colour, heat, FeCl;solution + dil.HCl, , , , , , , , , , , , , , Sulphur | SFE + dil.acetic acid + lead acetate Black ppt, , , , Halogen | SFE + dil. HNO3 , boil, cool, +AgNO; | White ppt-chlorine, , solution Pale yellow ppt-bromine, , , , , , , , , , Yellow ppt- iodine, , , , 22) Describe the estimation of carbon and hydrogen by Liebig’s method., A known mass of the organic compound is completely oxidized with cupric oxide in Leibig’s, apparatus. The C and H are oxidized to CO) and H2O respectively. The mass of CO) and, H2Oformed are determined by passing through anhyd. CaCl2 tube and KOH solution tube. From, these masses of CO; and HO, the % of C and H are calculated., % of C =12 x mass of COp x 100, 44 x mass of org. compound, % of H= 2 x mass of H)O x 100, 18 x mass of org. compound, 23) Describe estimation of nitrogen by Dumas method., A known mass of org. compound is heated with copper oxide in an atmosphere of CO. No gas,, CO, and water are formed. The mixture of gases produced is collected over an aqueous KOH, which absorbs CO». Nitrogen is collected in the upper part of the graduated tube., % of nitrogen= 28x Vx 100 — where w= mass of org. compd., 22400 x w, 2A) Describe estimation of halogens by Carius method., A known mass of org. compound is heated with fuming nitric acid in the presence of silver, nitrate contained in a hard glass tube(Carius tube). C and H are oxidized to CO) and HO. The, halogen forms the corresponding silver halide(AgX). It is filtered, washed, dried and weighed., % of halogen= Atomic mass of halogenxm x 100 where m= mass of AgX formed, Mol. mass of AgX x mass of org. compd., , (For diagrams ref. text books)