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7. Frequently Asked Questions on Density Determination
Q: I'd like to measure the density of a resin pellet or sheet, which floats in water. Is it
possible?
A: Use a liquid that has a lower density than water and does not dissolve the sample,
such as methanol (density 0.798) or kerosene (density 0.80). The density of the
liquid used is measured using the float provided with the kit.
Q: Can a sample containing bubbles be measured?
A: The density of a sample with bubbles contained can be measured as it is. But as
time passes, the bubbles disappear and the apparent density may change.
A sample, which floats on water due to the low density, can not be measured.
Q: The measurement repeatability may be affected by the water's surface tension.
What can I do about this?
A: A few drops of a surface-active agent (for example, a mild detergent for washing
dishes) added to the water reduces the influence of surface tension. A few drops of
a surface-active agent will affect the liquid density only a very small amount.
When methanol is used in place of water, the influence of surface tension is small,
even without a surface-active agent.
Q: When tap water is used, bubbles are gradually generated on the sample surface
and a measurement error occurs. What can I do about this?
A: Tap water contains dissolved gases such as oxygen and carbon dioxide. When tap
water is used, the released dissolved gases generate bubbles. It is recommended
that pure water or distilled water, which contains few dissolved gases, be used.
Q: I try to measure a high water repellent material such as rubber but bubbles stick to
the sample. What can I do about this?
A: Before measurement, soak the sample in the water with an appropriate amount of
surface-active agent added. Doing this increases the sample surface hydrophilicity
and bubbles may hardly stick to the sample surface.
Summary of Contents for GX-13
Page 5: ...3 1 The Kit Includes...
