Cleaning laboratory glassware isn't as simple as washing the dishes. Here's how to wash your glassware so you won't ruin your chemical solution or laboratory experiment.
Lab Glassware Cleaning Basics
It's generally easier to clean glassware if you do it right away. When a detergent is used, it's usually one designed for lab glassware, such as Liquinox or Alconox. These detergents are preferable to any dishwashing detergent that might be used on dishes at home.
Usually, detergent and tap water are neither required nor desirable. You can rinse the glassware with the proper solvent, then finish up with a couple of rinses with distilled water, followed by final rinses with deionized water.
Washing Out Common Chemicals
- Water Soluble Solutions (e.g., sodium chloride or sucrose solutions): Rinse three to four times with deionized water, then put the glassware away.
- Water Insoluble Solutions (e.g., solutions in hexane or chloroform): Rinse two to three times with ethanol or acetone, rinse three to four times with deionized water, then put the glassware away. In some situations, other solvents need to be used for the initial rinse.
- Strong Acids (e.g., concentrated HCl or H2SO4): Under the fume hood, carefully rinse the glassware with copious volumes of tap water. Rinse three to four times with deionized water, then put the glassware away.
- Strong Bases (e.g., 6M NaOH or concentrated NH4OH): Under the fume hood, carefully rinse the glassware with copious volumes of tap water. Rinse three to four times with deionized water, then put the glassware away.
- Weak Acids (e.g., acetic acid solutions or dilutions of strong acids such as 0.1M or 1M HCl or H2SO4): Rinse three to four times with deionized water before putting the glassware away.
- Weak Bases (e.g., 0.1M and 1M NaOH and NH4OH): Rinse thoroughly with tap water to remove the base, then rinse three to four times with deionized water before putting the glassware away.
Washing Special Glassware
Glassware Used for Organic Chemistry
Rinse the glassware with the appropriate solvent. Use deionized water for water-soluble contents. Use ethanol for ethanol-soluble contents, followed by rinses in deionized water. Rinse with other solvents as needed, followed by ethanol, and, finally, deionized water. If the glassware requires scrubbing, scrub with a brush using hot soapy water, rinse thoroughly with tap water, followed by rinses with deionized water.
Burets
Wash with hot soapy water, rinse thoroughly with tap water, then rinse three to four times with deionized water. Be sure the final rinses flow off of the glass. Burets need to be thoroughly clean to be used for quantitative labwork.
Pipets and Volumetric Flasks
In some cases, you may need to soak the glassware overnight in soapy water. Clean pipets and volumetric flasks using warm soapy water. The glassware may require scrubbing with a brush. Rinse with tap water followed by three to four rinses with deionized water.
Drying or Not Drying
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. Normally, you can allow glassware to air dry on the shelf. Otherwise, if you are adding water to the glassware, it is fine to leave it wet (unless it will affect the concentration of the final solution.) If the solvent will be ether, you can rinse the glassware with ethanol or acetone to remove the water, then rinse with the final solution to remove the alcohol or acetone.
Rinsing with Reagent
If water will affect the concentration of the final solution, triple rinse the glassware with the solution.
Drying Glassware
If glassware is to be used immediately after washing and must be dry, rinse it two to three times with acetone. This will remove any water and will evaporate quickly. While it's not a great idea to blow air into glassware to dry it, sometimes you can apply a vacuum to evaporate the solvent.
Additional Tips
- 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 lint-free towel soaked with ether or acetone. Wear gloves and avoid breathing the fumes.
- The deionized water rinse should form a smooth sheet when poured through clean glassware. If this sheeting action is not seen, more aggressive cleaning methods may be needed.
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