15
The proportion of the IR rays which does
not heat the sample is either reflected on
the surface of the sample or penetrates the
sample unimpeded .
The color and surface properties of the
sample significantly influence how effective
the heating process is . For example, dark
substances absorb IR rays better than bright
substances .
IR-Strahlung
Substanz
Wärmeenergie
IR rays
Heat
Substance
Dark substance
Low reflection
Bright substance
Strong reflection
How the rays penetrate the sample depends
on the permeability of the sample . If the
degree of light-transmitting capacity is low,
the rays can penetrate only the uppermost
layers of the sample . The heat conductivity
of the sample dictates the degree to which
the heat can be transmitted to the under-
lying layers . The higher the conductivity,
the faster and more uniformly the
substance is heated .
The substance should be applied to the
sample pan in a thin, even layer . A height
of approximately 2–5 mm for 5–15 g
substance weight has proved to be ideal .
Otherwise, the sample will not be dried
completely or the analysis time will be
unnecessarily extended, a crust/skin will
form on the surface of the sample or the
sample will scorch, and the analysis results
obtained will not be reproducible (and
hence cannot be used) .
Summary of Contents for MA35
Page 2: ......
