User manual

PBS-A03/A04-BA-e-1213 21
9 User Instructions
• To form a reproducible mean value several density measurement are necessary
• Remove fat from solvent-resistant sample / sinker /beaker.
• Regularly clean sample dishes/ sinker/beaker, do not touch immersed part with your
hands
• Dry sample/ sinker/pincers after each measurement.
• Adjust sample size to sample dish (ideal sample size > 5 g).
• Only use distilled water.
• When immersing for the first time, lightly shake sample dishes and sinker, in order to
Dissolve air bubbles.
• Always ensure that, when re-immersing into the liquid no additional bubbles adhere; it
is better to use pincers to place the sample.
• Remove firmly adherent air bubbles with a fine brush or a similar tool.
• To avoid adherent air bubbles smoothen samples with rough surface.
• Take care that no water drips onto the upper sample dish when weighing with the help
of tweezers.
• In order to reduce the surface tension of water and the friction of the liquid on the wire,
add three drops of a common detergent (washing-up liquid) to the measuring liquid
(density modification of distilled water occurring due to the addition of tensides can be
ignored).
• Oval samples can be held more easily with pincers when you cut grooves into them.
• The density of porous solids may only be determined approximately. Buoyancy errors
occur when not all the air is eliminated from the pores during immersion in the
measuring fluid.
• To avoid great vibrations of the balance, place sample carefully.
• Avoid static charge, e. g. dry sinker with cotton cloth only.
• If the density of your solid body just deviates slightly from that of distilled water, ethanol
may be used as measuring liquid. However, check beforehand whether the sample is
solvent-proof. In addition you must observe the applicable safety regulations when
working with ethanol.