Sartorius YDK 01-0D Betriebsanleitung Seite 19

Adhesion of Liquid to the Wire
When the sample holder (or sieve) is
immersed in liquid causing buoyancy,
liquid travels up the wire because
of adhesion forces and generates an
additional weight in the range of
a few milligrams.
Since the sample holder (or sieve) is in
the liquid causing buoyancy during both
weighing in air and weighing in liquid,
and the balance is tared at the beginning
of each measuring procedure, the effect
of the meniscus can be disregarded.
To reduce the surface tension and the
friction of liquid on the wire, add three
drops of a tenside (Mirasol Antistatic
or an ordinary dishwashing detergent)
to the distilled water in the beaker.
Because of the liquid travelling up the
wire, the weight may slowly change even
after the stability symbol "g" appears.
Therefore, read off the weight immediately
after the "g" is displayed.
Air Bubbles
The measuring error caused by air bubbles
adhering to the sample can be estimated
in the following manner. An air bubble
with a diameter of 0.5 mm causes an
additional buoyancy of less than 0.1 mg
when a sample is weighed in water. An air
bubble diameter of 1 mm causes additional
buoyancy of 0.5 mg and an air bubble
diameter of 2 mm causes approx. 4.2 mg
additional buoyancy. Larger air bubbles
must be removed with a fine brush or
other utensil.
You can also wet the sample in a separate
container before you weigh it.
19