Organic Chemistry – Some Basic Principles and Techniques

Discuss a suitable method for the estimation of halogens. - Wired Faculty

Question

Discuss a suitable method for the estimation of halogens.

Solution

Carius method for the estimation of halogens: A known mass of the organic compound containing halogens is heated with an excess of fuming nitric acid and silver nitrate in a sealed tube called Carius tube. Cabron, hydrogen and sulphur (if present) are oxidised to CO₂, H₂O and H₂SO₄respectively whereas halogen forms a precipitate of silver halide. The precipitate is separated, washed with distilled water, dried and weighed. The percentage of halogens is then calculated. Calculations:
Let the mass of the compound taken = Wg Let the mass of halide (AgX) formed = ag

Atomic mass of halogen = x
$space space therefore space space Molecular space mass space of space silver space halide space left parenthesis AgX right parenthesis space equals space 108 space plus straight x space space space AgX space equals space straight X space space left parenthesis 108 plus straight x right parenthesis space equals space straight x space Now space left parenthesis 108 plus straight x right parenthesis space straight g space of space silver space halide space contains space halogen space equals space xg space space space therefore space space space space straight a space straight g space of space silver space halide space contains space hydrogen space space space space space space equals space fraction numerator straight x over denominator left parenthesis 108 plus straight x right parenthesis end fraction cross times space ag therefore space space Percentage space of space halogen space equals space fraction numerator straight x space cross times space straight a over denominator left parenthesis 108 plus straight x right parenthesis space cross times space straight W end fraction cross times 100$
$therefore space space Percentage space of space chlorine space space space space equals space fraction numerator 35.5 space cross times space Mass space of space AgCl space cross times space 100 over denominator 143.5 space cross times space Mass space of space organic space compound end fraction Percentage space of space bromine space space space space space equals space fraction numerator 80 space cross times space Mass space of space AgBr space cross times space 100 over denominator 188 space cross times space Mass space of space organic space compound end fraction Percentage space of space iodine space space space space space space space space space space space space space equals space fraction numerator 127 space cross times space Mass space of space AgI space cross times space 100 over denominator 235 space cross times space Mass space of space organic space compound end fraction$

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Organic Chemistry – Some Basic Principles And Techniques

Discuss a suitable method for the estimation of halogens.

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