06/05-W97-Sel
Instruction sheet 666 173
6
Beckmann thermometer (666 173)
5
4
5
1 Thermometer bulb
2 Grinding NS 19/26
4
3 Mercury thread, over main scale
4 Overflow bulb
3
3
5 Capillary restriction
6 Auxiliary bulb, over auxiliary scale
2
1
1
0
2
Description
The Beckmann thermometer is intended for use in the temperature range from -30°C to +120°C for measuring temperature changes with a resolution of 0.01 K, and it enables freezing point depressions and boiling-point elevations to be measured at high accuracy.
At first the Beckmann thermometer has to be set to the desired
temperature by transferring mercury from the thermometer
bulb into the auxiliary bulb. The thermometer bulb then contains just so much mercury that the temperature change within
an interval of 5 K can be read from the main scale at the set
temperature. The auxiliary bulb takes up the excess mercury
from the thermometer bulb. At the same time, the set temperature can be read from the auxiliary scale.
2
Technical data
Division of the main scale:
5 : 0.01 K
Division of the auxiliary scale: 150 : 5 °C
1
Grinding:
NS 19/26
Total length:
60 cm
Safety notes
The Beckmann thermometer contains mercury.
- Block the wider vicinity at once.
Mercury is very toxic if it is inhaled, swallowed or if it gets
into contact with the skin. On contact with water or acid it
produces very toxic gases. While being used it can become
easy to ignite.
- Put remainders of the mercury into the mercury toxic
waste.
- Catch larger balls of mercury with a pipette and put it
into mercury toxic waste.
If the Beckmann thermometer breaks in spite of maximum
caution, you have to be particularly careful:
- Absorb small remainders of mercury with a special absorbent (Mercurisorb), and dispose of it.
Instruction sheet 666 173
3
Setting
Page 2/3
3.2 Setting a higher temperature:
If the set temperature is too low or if the mercury thread runs
upwards and exceeds the main scale, mercury has to be transferred from the thermometer bulb into the auxiliary bulb. If, on
the other hand, the set temperature is too high or if the mercury thread runs downwards out of the main scale, mercury
has to be transferred back into the thermometer bulb.
For measuring the freezing-point depression in a solution, the
Beckmann thermometer is set so that the freezing-point of the
pure solvent is on the upper part of the scale range on the
main scale. Then the lower part of the main scale is available
for the freezing-point depression.
For measuring the boiling-point elevation in a solution, the
Beckmann thermometer is set so that the upper part of the
main scale is available.
3.1 Bringing mercury together:
- Bring the mercury from the thermometer bulb and the auxiliary bulb together (see 3.1).
- Read the reached temperature from the auxiliary scale, and
wait until enough mercury has been transferred into the auxiliary bulb.
- End the setting procedure (see 3.4).
3.3 Setting a lower temperature:
- Hold the Beckmann thermometer vertically with the auxiliary
bulb directed downwards, and slightly tap the thermometer
until the separated part of the mercury is completely in the
auxiliary bulb.
- Wait until the overflow bulb and the capillary restriction are
filled without interruption (without bubble) and the mercury
thread then flows into the auxiliary bulb through the capillary
restriction.
- Bring the mercury from the thermometer bulb and the auxiliary bulb together.
- Carefully rotate the Beckmann thermometer until the auxiliary bulb is about 10 cm higher than the thermometer bulb
(thereby the mercury thread must not break at any place).
Now mercury slowly flows from the auxiliary bulb into the
thermometer bulb.
- Read the reached temperature from the auxiliary scale, and
wait until enough mercury has been transferred into the
thermometer bulb.
- End the setting procedure (see 3.4).
Page 3/3
Instruction sheet 666 173
3.4 Ending the setting procedure
- Carefully bring the Beckmann thermometer in an upright
position (thereby the mercury thread must not break below
the overflow bulb).
- Carefully tap the upper part of the thermometer in order that
the mercury thread breaks at the capillary restriction.
- Wait until the mercury has flowed out of the overflow bulb,
and check the setting.
LD Didactic GmbH . Leyboldstrasse 1 . D-50354 Huerth / Germany . Phone (02233) 604-0 . Fax (02233) 604-222 . e-mail: [email protected]
by LD Didactic GmbH
Printed in the Federal Republic of Germany
Technical alterations reserved