A second approach to gravimetry is to thermally or chemically decompose a
solid sample. The volatile products of the decomposition reaction may be
trapped and weighed to provide quantitative information. Alternatively, the
residue remaining when decomposition is complete may be weighed. In
thermogravimetry, which is one form of volatilization gravimetry, the
sample’s mass is continuously monitored while the applied temperature is
slowly increased.
Whether the analysis is direct or indirect, volatilization gravimetry requires
that the products of the decomposition reaction be known. This requirement
is rarely a problem for organic compounds for which volatilization is usually
accomplished by combustion and the products are gases such as CO2, H2O,
and N2. For inorganic compounds, however, the identity of the volatilization
products may depend on the temperature at which the decomposition is
conducted.
The products of a thermal decomposition can be deduced by monitoring the
sample’s mass as a function of applied temperature. (Figure 8.9). The loss of
a volatile gas on thermal decomposition is indicated by a step in the
thermogram. As shown in Example 8.4, the change in mass at each step in a
ther- mogram can be used to identify both the volatilized species and the solid
residue.
,
solid sample. The volatile products of the decomposition reaction may be
trapped and weighed to provide quantitative information. Alternatively, the
residue remaining when decomposition is complete may be weighed. In
thermogravimetry, which is one form of volatilization gravimetry, the
sample’s mass is continuously monitored while the applied temperature is
slowly increased.
Whether the analysis is direct or indirect, volatilization gravimetry requires
that the products of the decomposition reaction be known. This requirement
is rarely a problem for organic compounds for which volatilization is usually
accomplished by combustion and the products are gases such as CO2, H2O,
and N2. For inorganic compounds, however, the identity of the volatilization
products may depend on the temperature at which the decomposition is
conducted.
The products of a thermal decomposition can be deduced by monitoring the
sample’s mass as a function of applied temperature. (Figure 8.9). The loss of
a volatile gas on thermal decomposition is indicated by a step in the
thermogram. As shown in Example 8.4, the change in mass at each step in a
ther- mogram can be used to identify both the volatilized species and the solid
residue.
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