Chapter 4: Using Your RapidVap
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Original instructions
Calculating the boiling point:
The operating pressure corresponding to the desired boiling point temperature may
be calculated for any solvent using the following formula:
log P = 2.8811 – Ta – T
(b)(T)
Where P = Vacuum (mm Hg)
Ta = Boiling Point Temperature at Atmospheric
Pressure (°K)
T = Desired Boiling Point Temperature (°K)
b = Constant from Table
Useful conversion factors:
1 mBar = .75 mm Hg
°K = °C + 273
Using the nomogram:
To use this graph, three facts must be known about a given solvent:
1.
Boiling point at normal atmospheric pressure (1 Bar).
2.
Constant b.
3.
Either operating temperature or operating pressure.
To determine the desired boiling point at a given pressure:
1.
Find the boiling point at normal atmospheric pressure (1 Bar) on the left side of
the graph.
2.
Find the operating pressure on the right side of the graph.
3.
Draw a straight line linking these two points.
4.
Find “Constant b” for the solvent on the top of the grid. Follow that line until
it intersects with the line as drawn between the two points. This point
represents the boiling point at the given pressure and the temperature is read
off the left or right side of the grid (0-250°C).
To determine the operating pressure necessary to achieve a given boiling
point:
1.
Find the boiling point at normal atmospheric pressure (1 Bar) on the left side of
the graph.
2.
Find the “Constant b” and follow this line to the desired boiling point on the
grid (0-250°C).
3.
Draw a straight line linking these two points and extrapolate on the right hand
scale to find the operating pressure.
