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Boiling Method -
- The Boiling method can be used as a simpler, alternative method to the distillation method or to to confirm results obtained through the distillation and hydrometry method.
- This method follows the distillation method, however, uses the difference in specific gravity of the wine sample before and after the alcohol has been removed by boiling.
- Procedure -
1. - Measure the specific gravity of your cleared wine sample and record the measurement along side the temperature the measurement was taken at.
2. - Correct for the temperature difference between the recorded temperature and the temperature the hydrometer was calibrated at, using the chart values for hydrometers calibrated at 20oC, and record the true specific gravity of the wine sample as SG1.
3. - Measure out exactly 250ml of the wine sample in a 250 ml volumetric flask - (see method)
4. - Empty the wine out of the volumetric flask into the distillation flask and employ a couple of distilled water rinses to remove wine residues from the volumetric flask into the distillation flask.
5. - Add some boiling chips to the distillation flask to prevent bumping when boiling the contents.
Caution: do not add the boiling chips once heating has commenced.
6. - Set up apparatus as per diagram using only the boiling flask. A vertical splash head may be fitted if desired.
6. - Apply heat to the bottom of the boiling flask and boil the wine down to approximately 125ml.
If the heat from the burner is to local or intense, position a tripod and heat diffuser (gauze), to disperse the applied heat, between the heat source and boiling flask.
7. - Allow the wine to cool down and using a funnel, carefully pour the remaining wine into the same 250ml volumetric flask used to measure the wine volume at the start.
8. - Rinse out the remaining wine residues with a few rinses of distilled water, into the same volumetric flask.
9. - Top up the contents of the volumetric flask with distilled water close to 250 ml, bring to 20oC in a hot water bath, then top up to the 250ml graduation mark. Stopper and mix (see method).
10. - Use a small amount the collected, diluted distillate to rinse a clean 250ml measuring cylinder. Then fill a 250ml measuring cylinder with the distillate.
11. - Using an specific gravity hydrometer, measure the specific gravity of the alcohol depleted wine solution and record your reading.
12. - Using a thermometer measure the temperature of the solution and record your reading.
13. - Correct for the temperature difference between the recorded temperature and the temperature the hydrometer was calibrated at, using the chart values for hydrometers calibrated at 20oC, and record the true specific gravity of the alcohol depleted wine solution as SG2.
13. - Using the equation below to calculate the alcohol concentration of you wine sample and record the result.