INSTRUMENT MAINTENANCE
PRACTICAL TASK P6. REFRACTOMETER Outline The optics in a refractometer could become misaligned over time, and would give an inaccurate reading. Measuring against a material of known RI is the only way to determine this. RI does vary with temperature so this must be corrected for. Procedure 1. Clean the two glass faces of the refractometer with water, then propanone. 2. Switch the instrument on and leave for 10 minutes to warm up. 3. Add 3‐5 drops of distilled water to the bottom plate, clamp and measure the RI. 4. Measure the temperature of the water from the container you used for the measurement. 5.
For each degree above 20C, subtract 0.00045 from the reading. For values below 20, add 0.00045/degree. Reporting Requirements Use the standard Performance Check reporting sheet. Acceptable range: 1.3330 ± 0.001