Solvent Data - Heidolph LABOROTA 20 control automatic Betriebsanleitung

The T mode includes the following features:
auto

(Temperature sensor needs to be installed)

Selective distillation of substances does not need manual pressure setting

Easy to reproduce

Easy setting

No need to know about thermodynamic substance data

first choice for low-pollution / zero-loss distillation.

Due to its location, the temperature sensor detects coolant temperature as an approximate
only. Set T auto values of 2 – 8°C above coolant temperature for optimum reproducibility.
Increasing this temperature span results in a higher rate of distillation with a decrease in
reproducibility.

3. Solvent data


Examples for using table and chart:

The table displays essential substance data, the chart makes reference to the relationship
between pressure and boiling point of some solvents. In this case, 1/T is plotted as a function
of log p in accordance with the Clausius-Clapeyron equation.
a) Distillation of a solvent contained in the table:

on the LABOROTA 20 control set the value from column "vacuum for set point at 40°C" as
reference value for Set Vacuum.
b) Distillation of a solvent contained in the chart, with a boiling point other
than 40°C:

Mark the boiling point desired on the temperature axis of the chart

Draw a line to the right to get an intersection with the solvent

Vacuum pressure required for this one situation is found by drawing a vertical line from this
intersection down to the horizontal axis.
c) Distillation of a solvent not contained in the table or chart:

The following notes may be helpful to determine the appropriate vacuum pressure:

The line gradient is a function of enthalpy of evaporation. It is similar for chemically related
substances with boiling points close to each other. Hence, the plotted lines may be used as a
guide for substances with slightly different boiling points.

Using a water-jet or diaphragm-type pump, you may lower boiling point by approx. 100°C.

Rule of thumb: decrease pressure to a half will lower boiling point by approx. 15°C.
Avoid overpressure in the glassware kit while distilling low-boiling solvents. Aerate
glassware kit as required. Overpressure in the glassware kit may damage the evaporator
or even blow-up parts of the glassware kit.
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