Appendix B
B–58 TA I
NSTRUMENTS
TGA 2950
Hi-Res
TM
TGA
Examples
Included in this section of the manual are
example TGA scans of common materials.
These examples can be used to compare the
results of using Hi-Res
TM
TGA heating control
with the results of conventional constant heating
rate TGA. Where possible the effects of using
the different Hi-Res
TM
modes and parameters are
shown.
Mixture of
Bicarbonates
A mixture of potassium bicarbonate (potassium
hydrogencarbonate) and sodium bicarbonate
(sodium hydrogencarbonate) was chosen to
demonstrate the effects of different Hi-Res
TM
techniques and parameter settings. The indi-
vidual bicarbonates decompose to carbonates
between 100
°
C and 200
°
C with the simultaneous
release of CO
2
and H
2
O. Potassium bicarbonate
decomposes at approximately 50
°
C higher
temperature than sodium bicarbonate. When
mixed together the decompositions of the two
bicarbonates are overlapped in temperature and
are very difficult to resolve. You can easily
make this sample yourself by thoroughly mixing
equal parts (by weight) of finely powdered
potassium bicarbonate (KHCO
3
) and sodium
bicarbonate (NaHCO
3
). Inadequate mixing or
large granule size will reduce weight loss
reproducibility. Note that potassium bicarbon-
ate is very hygroscopic. The mixture must not
be exposed to ambient humidity for long or a
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