Barloworld Scientific Stuart SMP11 Instrucciones De Funcionamiento página 4

Measuring a melting point
N.B. If the unit has been used recently the block
may be too hot for your sample. If this is the case
turn the apparatus off and allow the unit to cool
before proceeding. An optional brass cold finger
(ref. SMP1/2) can be inserted into the
thermometer hole; this has the effect of drawing
heat out of the heating block and so considerably
reduces the cooling time.
1. The SMP11 is supplied with a pack of 1.9mm
open-ended capillary tubes. It is recommended
that one end of the tubes should be sealed
with a Bunsen burner flame, by a fully trained
person, prior to use. Alternatively a pack of
capillary tubes that have been sealed on one
end can be purchased from your Stuart
stockist (ref. SMP10/1).
2. Place a small amount of your powdered
sample into the end of a 1.9mm diameter
glass capillary tube.
3. Insert the capillary tube into the side of the
heating block via the holes provided (see Fig
4). A maximum of 3 capillary tubes can be
inserted at any one time.
Capillary tube
Thermometer
Fig 4
4. Look down the lens and position the tube so
that the sample can be observed clearly
(see Fig 5).
2
Heating block
Thermometer
Capillary tube
Fig 5
5. It is assumed that the approximate melting
point range is known, if not a rough run may
be required to gauge the approximate range.
6. In order to achieve a fast and accurate
melting point range it is important to use a
rapid heating rate as the sample heats up
from ambient and a much reduced heating
rate as the sample approaches melt, see Fig
6 for an ideal heating curve for a sample
with a melting point of 240°C.
Ideal heating curve
Dial settings
Max
300
250
200
150
100
50
0
0 2 4 6 8
Fig 6
7. Connect to the mains electricity supply.
8. Start by heating the sample at the maximum
rate by setting the heating controller to max.
Caution: The heating block may be HOT.
Block temperature
Melting point
10°C/min 1°C/min
10 12 14 16 18 20
Time (min)
Lens
22 24 26