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Cleaning of Special Glassware
a. Cleaning Burets
1.Wash with soapy water
2.Rinse thoroughly with tap water
3.Then rinse three to four times with deionized water. The rinse should form a smooth sheet when poured through clean glassware. If this sheeting action is not seen, more aggressive cleaning is needed.
4.Burets need to be thoroughly cleaned to be used for quantitative work such as titrations. To expedite the glass drying process, rinse again with a small volume of acetone to remove water. The used acetone will then go into organic waste.
b. Cleaning Pipets and Volumetric Flasks
1.Clean pipets and volumetric flasks using warm soapy water
2.Rinse with tap water followed by three to four rinses with deionized water. This water rinse should form a smooth sheet when poured through clean glassware. If this sheeting action is not seen, more aggressive cleaning may be needed.
3.Dry using acetone to remove water. This acetone rinse will be disposed of in the organic waste container.
NB/ If water will affect the final solution, you can rinse with the solution you’re using to remove the water. Then, triple rinse with the solution you’re using to remove the alcohol or acetone.
Remove stoppers and stopcocks when they are not in use. Otherwise, they may “freeze” in place.
You can de-grease ground glass joints by wiping them with a kimwipe soaked with hexane or acetone. Do this in the hood vent to prevent you from breathing in the chemicals.
Do NOT dry glassware with a paper towel or forced air. This can introduce fibers or impurities. Normally, you can allow glassware to air dry on the shelf. Otherwise, if you need to turn in glassware to the stockroom you can use a solvent as described above
Rinsing with Reagents
If water will affect the concentration of the final solution, triple rinse the glassware with the solution that is intended to be used.
If glassware is to be used immediately after washing and must be dry, rinse it 2-3 times with acetone. This will remove any water and will evaporate quickly. While it is not a great idea to blow air into glassware to dry it, sometimes you can apply a vacuum to evaporate the solvent.
Drying Glassware
After washing and rinsing, you can allow glassware to air dry while facing upside down on clean rack before returning them to shelf.
It is inadvisable to dry glassware with a paper towel or forced air since this can introduce fibers or impurities that can contaminate the solution. If the solvent will be ether, you can rinse the glassware with ethanol or acetone to remove the water, and then rinse with the final solution to remove the alcohol or acetone.
For apparatus having stoppers or stopcocks, remove them when they are not in use. Otherwise, they may ‘freeze’ in place.
Cleaning of Plastic wares
Cleaning laboratory plastic ware depends on the type and properties of the plastic.
Cleaning of some plastic apparatus under extreme heat or cold may affects their flexibility and strength.
Also Chemicals such as lubricants and oil cause cracking, and prolonged use of oxidizing agents cause brittleness and breakage.
Laboratory plastic wares made of polyethylene and polypropylene are subject to reaction between container and sample, this can give incorrect results.
Cleaning methods for plastic wares
a.Acid bath
An acid bath is a container containing acid in which the plastic ware is placed and kept for some time until clean.
a)Immerse plastic ware into the acid eg 1M nitric acid and allow to soak overnight for mild contamination.
b)Keep in bath for about one week for heavy contamination. The cleaned plastic ware is then taken out of the bath, rinsed with distilled water, and put to dry.
c)A rinse with acetone or placement in a glassware dryer at low temperature can be used.
Note: Plastics tend to float when put into the cleaning solution and can be sunk to the bottom using a pair of tongs
b.Autoclaving
Some plastic wares can also be cleaned by autoclaving. However, they must be autoclaved within the temperature range they can tolerate.
a)Rinse thoroughly with distilled water before autoclaving.
b)Remove any stoppers, caps or fittings before autoclaving.
Plastic containers such as vials, sample tubes and bottles should be autoclaved with their closures disengaged to avoid deformation.