8 13681.03 Question 3 Requirements • Retort stand, boss head and clamp • Granulated sugar • Plastic tray, dimensions approx. 20 cm × 15 cm, depth 3–5 cm • Metre rule • Marble, approx 1.5 cm diameter • Vernier caliper • 30 cm ruler Preparation Fill the tray with the sugar so that the surface of the sugar is approx. 0.5 cm below the edge of the tray. Before the examination Clamp the metre rule into the retort stand and set the zero of the metre rule at the surface level of the sugar as shown in Fig 3.1. Check that the surface of the sugar is fl at. metre rule clamp surface retort stand Fig 3.1 Place the marble and the 30 cm ruler close to the apparatus. Action at changeover Return the apparatus to its original arrangement on the desk. Smooth the surface of the sugar.