Basic Principles
Purpose
The moisture analyzer can be used for quick and reliable determination of the
moisture content of materials of liquid, pasty, and solid substances using the
thermogravimetric method .
Material
The moisture of a sample is often mistakenly equated to its water content .
In fact, the moisture of a material includes all of the volatile components which
are emitted when the sample is heated, and lead to a reduction in its weight .
Among such volatile substances are:
– Water
– Fats
– Oils
– Alcohols
– Organic solvents
– Flavorings
– Volatile components, products of decomposition (when a sample is overheated)
There are many methods for determining the moisture content of a substance .
Basically, these methods can be divided into two categories:
When absolute methods are used, the moisture content is directly determined
(for example, as a weight loss registered during the drying routine) . These methods
include oven drying, infrared drying, and microwave drying . All three of these
methods are thermogravimetric .
When deductive methods are used, the moisture content is indirectly determined .
A physical property related to the moisture in the substance is measured (e .g .,
conductivity) . These methods include capacitive and spectroscopic processes .
Thermogravimetry is the process of determining the loss of mass that occurs when
a substance is heated . In this process, the sample is weighed before and after being
heated, and the difference between the two weights is calculated .
In a conventional drying oven, circulating hot air warms the sample from the
outside to the inside . Efficiency is lost during drying because as the moisture
evaporates, it cools the sample surface .
By contrast, infrared rays (IR rays) penetrate a sample without being impeded .
Having reached the interior of a sample, they heat the sample directly .
IR-Strahlung
Substanz
Wärmeenergie
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Operating Instructions Moisture Analyzer MA37
Basic Principles
