Pycnometer
Asri Ambarwati 141424006Dahliana Alami 141424008PYCNOMETER AND
HYDROMETER
Pycnometer Picnometer is a special glass flask which is used for
determining a density of liquids using the weight of a known
volume. It usually has a glass faceted cork which is pierced in the
centre like a thin capillary through which surplus of liquid runs
out.There are several sizes of pycnometer, which is: 10 ml, 25 ml,
50 ml and 100 ml
However, the more frequently used is 10 and 25 mL pycnometer
TypesPycnometer With ThermometerPycnometer Without
Thermometer
How It Works
This method is based on the measurement of the density of
unknown liquid by the help of the density of known liquid with the
same volumes. This volume is realized by the pycnometer.
How To Operate The DeviceIt must be dry for the accurate
determination of its mass. It is important that the stoppers are
not exchanged from bottle to bottle, since each stopper is ground
to fit one bottle and no other. Weigh the clean dry bottle. Obtain
approximately 15 mL of the unknown liquid. Pour the liquid into the
specific gravity bottle until the bottle is completely full. Insert
the stopper so the ground glass (frosted) end is in the bottle.
Carefully dry the outside of the bottle with a tissue and
weigh.
Pour the unknown liquid down the sink and rinse the bottle
several times with distilled water. (The unknown liquids are
aqueous based and can be poured down the sink.) Fill the bottle
with distilled water, dry the outside and weigh. Determine the
temperature of the distilled water. Calculate the volume of the
pycnometer using the literature value for the density of water at
the temperature of the water. Calculate the specific gravity and
density of the unknown liquid.
SAFETYThe pycnometer is delicate and expensive; exercise care
when handling it. The bulb and stopper of the pycnometer are both
engraved with the same number. Be sure that you do not
inadvertently switch stoppers with someone else; check the numbers
occasionally. The pycnometer must be clean and DRY before the
initial weighing. To fill the pycnometer with liquid, use a Pasteur
pipet to fill the bulb to about halfway up the neck (there is
usually a white mark). Then slowly insert the capillary
stopper.When full, there should be NO air bubbles in the bulb or
capillary of the pycnometer, and no air space at the top of the
capillary. Before weighing the full pycnometer, the outside should
be perfectly dry.
HydrometerA hydrometer is a tool scientists use to measure
thespecific gravityof liquids.Hydrometer is usually made of glass
and consists of a cylindrical rod and ball weighting with mercury
to make it float.
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How it worksThe hydrometer operates on Archimedes Principle.
Archimedes , an ancient Greek mathematician, discovered that when a
body lighter than a fluid is placed in that fluid, the fluid
displaced by the body will equal the volume of the body as well as
the mass or weight of the body. This principle is better known as
buoyancy.
How To Operate The DeviceUsing a hydrometer is quite simple. The
user must be careful, though, to not break the hydrometer or the
cylinder as they are made from glass. Follow the easy to follow
directions below.Fill the glass cylinder with sample water.Put the
hydrometer with the bulb end down. It will bob up and down in the
sample. Note that the sample may overflow from the cylinder.Assure
that the hydrometer is not in contact with the sides of the
cylinder and take the reading.
Extreme care should be taken when reading the hydrometer; it is
very easy to misinterpret the scale. Once the hydrometer has
stopped bouncing up and down and the hydrometer is not touching the
walls of the cylinder, a reading can be made. Note that a meniscus
forms on the neck of the hydrometer. Just as reading the meniscus
in a graduated cylinder, the user must take the reading where the
plane of water is and not where the water clings up the neck of the
hydrometer. See the image to the right. The correct reading of this
hydrometer is about 0.982.
Safety of HydrometerHydrometers should be stored in clean, dry,
safe places. They also should not be subjected to extreme
temperatures.
Referancehttp://www.lumcon.edu/education/K-12/studentdatabase/hydrometer.asphttp://glossary.periodni.com/glossary.php?en=picnometerhttp://wakeriko.blogspot.com/2011/11/piknometer.htmlhttp://s3.amazonaws.com/ppt-download/hidrometer.html
http://www.hbinstrument.com/hydrometer-faqs/http://artikelteknikkimia.blogspot.com/2011/12/hidrometer-alkoholmeter.html
