The micro boiling point is critical in providing an accurate measurement of a compound’s boiling point. This specific moment, when the last bubble escapes from the bottom of the bell and the liquid starts to rise, is significant for a few reasons.
Firstly, the generation of bubbles indicates that the compound has reached its boiling point. Bubbles form when vapor pressure equals atmospheric pressure, and this occurrence signifies that the liquid is transitioning into vapor. Therefore, the last bubble leaving the bottom of the bell represents the last instance where the liquid is in complete equilibrium with its vapor phase.
Additionally, as the bubbles rise and escape, they create a clear space above the liquid. This moment is key because it transitions the liquid from a stable boiling condition to a dynamic state where vapor starts to fill the space at the top of the bell. Recording the boiling point at this precise moment ensures that the measurement reflects the temperature at which the vapor phase is beginning dominantly. This avoids inaccuracies that may arise if the reading is taken at a point where liquid is still boiling vigorously or while bubbles are still forming excessively.
In summary, determining the boiling point at this exact point—when the last bubble leaves the bottom and the liquid begins to rise—provides a reliable indication of the boiling temperature, making the measurement more consistent across different trials.