Why is thermometer placement important in distillation?
Also, why should the bulb of the thermometer be placed?
The bulb part of the thermometer is positioned near the side arm of the Y-adaptor so that it monitors the temperature of the vapors. If it is too low, it will be too close to the boiling liquid and will read higher than the true vapor temperature.
One may also ask, why is the exact placement of the thermometer important when measuring a boiling point of a distillate what happens if it is too high or too low? A: •Placing the thermometer too high will lead to a low value for boiling point - be sure all the mercury in the bulb is below the sidearm of the still head. Inadequately clamping the apparatus can be dangerous. Over clamping can be a problem, since it causes stress in the apparatus. Remember to use boiling chips.
In this regard, why should the bulb of the thermometer be located just below the sidearm of the distilling flask?
The thermometer is positioned so the bulb is situated just below the sidearm of the 3-way. If the bulb is too the low, the heater would cause the temperature seen to be too high causing premature switching of the collecting flasks.
What happens if the thermometer is too high in distillation?
If the bulb of the thermometer or tip of the thermocouple is placed too high in the condenser, then the hot vapors are likely to condense before they reach the thermometer. This will result in the recorded temperature being lower than the actual boiling temperature of the vapor.