Presentation1
- 1. Kendriya Vidyalaya No.1 G.C.F. Chemistry Name : Viplovesh Chaudhary Class : XI Section : 'A'
- 2. Estimation of Nitrogen Principle: A known mass of the organic substances is heated with excess of copper oxide in an atmosphere of CO2 .Carbon, hydrogen and sulphur (if present) are oxidised to CO2, H2O, SO2 while nitrogen gas is set free. Any oxide of nitrogen that may be formed is reduced back to free nitrogen by passing over a hot reduced copper gauze. The two most commonly used methods for the estimation of nitrogen in organic compounds are: (1) Duma’s method (2) Kjeldahl’s method Duma’s method: This method is applicable to all organic compounds containing nitrogen and is briefly discussed below :
- 3. Apparatus: The apparatus used for estimation of nitrogen by Duma’s method is shown in Fig (a). It consists of three parts: (a) carbon dioxide generator (b) combustion tube and (c) Schiff’s nitro meter Apparatus for the estimation of nitrogen by Duma’s Method
- 4. Kjeldahl’s method: This is a more convenient and simpler method for the estimation of nitrogen and is largely used for the estimation of nitrogen in fertilizers, food stuffs, drugs, etc. Apparatus for estimation of nitrogen by Kjeldahl’s method
- 5. Estimation of halogens Carius method is used for estimation of halogens Principle: A known mass of the organic compound is digested (heated) with conc. . H2SO4 in presence of potassium sulphate and a little copper sulphate or mercury in a long - necked flask called Kjeldahl’s flasks {Fig (b)}. Potassium sulphate raises the boiling point of and thus ensures complete reaction while copper sulphate or mercury catalyses the reaction. Principle: A known mass of the organic substances is heated with fuming nitric acid and a few crystals of silver nitrate in a sealed hard glass tube (about 2cm wide & 50cm long) called Carius tube in a furnace (fig. a). Calculations: Let the mass of the substances taken = wg and the mass of the silver halide (AgX) formed = xg
- 6. Now, 1 mole of AgX contains 1 gram atom of X (X=Cl,Br or I) i.e. (108 + At. mass of X)g of AgX contains = (At.mass of X)g xg of AgX contains X = At.mass of x/108 + At.mass of X * x* xg . . . A Carius tube for estimation of halogens
- 7. Estimation of sulphur Principle: A known mass of the substances is heated with sodium peroxide or fuming nitric acid in a sealed tube (Carius tube). Carbon and hydrogen are oxidised to CO2 and H2O respectively while sulphur present in the compound is oxidised to sulphuric acid which is then precipitated as barium sulphate by adding excess of barium chloride solution.