Estimate the fat content of the given food by the Soxhlet method. Draw the apparatus.

1. 1 · Aim. To find the fat content of the given food sample by the Soxhlet method (observed during the lab visit).
2. 2 · Principle. Fat dissolves in petroleum ether. The solvent boils, condenses, drips on the sample in a thimble and siphons back with the fat, again and again; the fat collects in the pre-weighed flask.
3. 3 · Requirements. [Diagram: round-bottom flask, extractor with thimble and siphon tube, reflux condenser, water bath] Petroleum ether, thimble, oven, desiccator, balance.
4. 4 · Procedure.
   • Weigh the dried flask (W₁).
   • 2-5 g dried, ground sample (W) in the thimble.
   • Extract with petroleum ether for about 6-8 h on a water bath.
   • Recover solvent; dry the flask at 105 °C; cool; weigh (W₂) to constant weight.
5. 5 · Observation. [Table: W = 5.000 g | W₁ = 92.350 g | W₂ = 93.330 g]
6. 6 · Calculation. Fat = W₂ − W₁ = 0.980 g; % fat = 0.980 ÷ 5.000 × 100 = 19.6% (dry basis).
7. 7 · Result. The fat content of the given sample is ___ g per 100 g. It is reported as crude fat.
8. 8 · Precautions.
   • Flammable solvent: no flames, water bath or mantle, fume hood.
   • Condenser water on before heating; never boil dry.
   • Dry sample; desiccator cooling; constant weight; gloves and goggles.

Scoring tip: A neat, labelled diagram of the Soxhlet set-up and the cycle in five or six arrows carry most of the marks.