analysette 22 „ECONOMY“ Page 29
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Example: Slightly magnetic materials
Generally, it is virtually impossible to determine the particle
size distribution in magnetic materials in suspension, as
they individual particles attract each other. Thanks to the
high sensitivity of the "analysette 22" device, it is however
possible to process suspensions of low concentration -
where the distances between the particles are relatively
large. As the centrifugal pump has a high output rate, the
material can also be suspended in liquids of a high viscos-
ity.
If larger particles or particles with a high density are to be
measured, glycerol might be added to a ratio of 7: 3. The
device is able to process liquid with a viscosity of up to 30
cPoise without any problems to the pump system and the
dispersing unit.
8.4 Dispersion of samples with poor wettability
To disperse hydrophobic samples produce a dough, adding
a surfactant (Fairy Liquid) and gradually disperse in water
will stirring.
The use of external ultrasonic baths is recommended to
disperse agglomerates, as they allow for a better overall ul-
trasound treatment of the sample. As the integrated ultra-
sonic bath is part of the dispersing cycle, only the material
in the bath is treated.
For soil samples, we recommend using 0.1% to 0.5% so-
dium pyrophosphate solution to facilitate dispersion. The
sample prepared in this way in the ultrasonic bath (e.g. "la-
borette 17") can subsequently be measured in water.
8.5 Processing of samples with poor solubility
Even samples with poor solubility can be measured with
the "analysette 22" laser particle sizer. We recommend us-
ing a saturated sample liquid. In such a solution, the parti-
cle size is not affected by the solving process so that the
measured result will accurate. (Saturated solutions must be
filtered before they are processed)
In the case of extremely expensive materials, it might be
possible to use a replacement substance that facilitates
saturation of the sample liquid.
