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