Air Bubbles - Mettler Toledo 33360 Mode D'emploi

3.6 Air bubbles

With poorly wetting liquids such as water without wetting agents, for example, it is possible that air bubbles will
adhere to the submerged solid body, sinker or wire basket of gem holder. Because of their buoyancy, these
bubbles could affect the result. Thus, a bubble 1 mm in diameter would cause a buoyancy of 0.5 mg, while a bubble
with a diameter of 2 mm would result in a buoyancy of as much as 4 mg.
Precautionary measures:
- Degrease solids that are resistant to solvents.
- Periodically clean gem holder and sinker; do not touch immersible parts with your hands.
- Gently shake gem holder when first immersing it in liquid, before suspending it from hook, so as to loosen air
bubbles that might stick to it.
- Use wetting agents or organic solvents as auxiliary liquid (e.g. Kodak Photo-Flo, Pervitro 75% 72409).
(The change of density caused by the addition of a wetting agent to distilled water is negligible. If, for
example, 0.1 ml wetting agent with a density of 1.2 is added to 250 ml of water, the overall density changes
by 0.001 g/ml.)
3.7 Porous bodies
Since the submersion of porous bodies does not generally cause a one hundred percent displacement of air within
the pores by the liquid, errors will occur as a consequence. Thus the density of the body can only be approximated.
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