Sartorius YDK03 Mode D'emploi page 15

Determining the Specific Gravity of Solids
with a Density Less Than 1 g/cm
There are two different methods for
determining the specific gravity of solids
with a density less than 1 g/cm�
Method 1:
For this method, distilled water is still
used as the liquid causing buoyancy,
but the pan hanger assembly is replaced by
the sieve for immersing samples�
To determine the sample's buoyancy,
float it on the surface of the water and
then immerse it using the sieve�
It is also possible to use forceps or a similar
tool to place the sample directly under
the sieve (without removing the sieve from
the frame)�
If the buoyancy of the substance to be
measured is so high that the weight
of the sieve is not enough to immerse the
sample, increase the weight of the sieve
by adding an additional weight to the
upper pan on the frame�
Method 2:
3
(for this method, use the sample holder)
Here, use a liquid for causing buoyancy
with lower density than that of the solid
for which the specific gravity is to be
determined� We have had good results
with ethanol (up to a density of approx�
0�8 g/cm
The density ρ (fl) of ethanol (with reference
to its temperature) can be found in the
table in the supplement�
The negative effect of the liquid's surface
tension on the results is less noticeable
when ethanol is used than when distilled
water is employed� Therefore, it is not
necessary to add tensides�
When working with ethanol, you must
observe the valid safety precautions.
Use Method 2 if the density of the solid
varies only slightly from that of distilled
water� Since the sample is suspended
in water, measuring errors may occur if
the first method is used�
It also makes sense to use the second
method when determining the specific
gravity of a granulated substance,
since it would be difficult to get the entire
sample under the sieve as required when
performing the first method�
Do not use ethanol if the sample could
be attacked or dissolved by it�
3
)�
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