Preparing 30 wt% KOH - NanoLabStaff/nanolab GitHub Wiki

Preparing 30 wt% KOH

[!CAUTION]

  • Should be carried out in the Chemical Area
  • When you are not wearing PPE, ensure that the KOH pellets are not in contact with water
  • The reaction between the KOH pellets and water is exothermic. The solution will therefore heat up when mixed
  • The K ions are mobile and may penetrate normal glassware. Additionally, it is damaging to several processes. You should therefore only use the assigned KOH glassware/Teflon beakers
  • A buddy is needed for this process

You need:

  • 300 g of KOH pellets (chemical cleanroom: chemical cabinet by the washing machine)
  • 1000mL volumetric flask for KOH (chemical cleanroom: KOH cabinet)
  • 400mL beaker for KOH (chemical cleanroom: KOH cabinet)
  • Magnetic stirrer + magnet stick for KOH (KOH cabinet in ISO5) - magnetic stirrer platform
  • Funnel (chemical cleanroom: KOH cabinet)
  • Plastic spatula and plastic weighing cup (chemical cleanroom: disposables drawer)
  • DI water squeeze bottle
  • 1000mL plastic storage flask (gowning room) - Free standing scale without glass chamber for KOH measurements - Its important to not have the chamber so that the largest weighing cup fits.
  • PPE: Apron, yellow gloves, face shield (chemical cleanroom) - Always check the integrity of the yellow gloves, if they have drastic variation in coloring or have started to crack, do not use them.

Procedure:

  1. Weigh 300 g of KOH pellets using a plastic spatula and 2 of the largest plastic weighing cups. This does not require PPE as long as you make sure the pellets are not in contact with water.
  • These should be divided the two plastic cups so that there is roughly 150g in both. Write down the amount.
  1. Rinse the storage flask, beakers, volumetric flasks, funnels magnetic stirrer etc. with DI water before you start.
  2. Add 250 mL DI water into the beaker with a magnetic stirrer.
  3. After you have started the magnetic stirrer, slowly add the pellets from one of the weighing cups little by little (exothermic reaction!). Let it stir until the solution is clear before adding more.
  4. Rinse the plastic weighing cup with DI water into the beaker . Attempt to use as little DI water as possible as rinsing will be done several times.
  5. Transfer the solution to the volumetric flask using a funnel which is cleared for KOH.
  6. Repeat points 3, 4 and 5 with the remaining tray of pellets.
  7. Rinse the beaker with DI water and add the rinse to the volumetric flask using funnel.
  8. Rinse the funnel and magnetic stirrer into the volumetric flask.
  9. Top off with DI water until the meniscus tops the 1000mL mark.
  10. Turn the volumetric flask 4 times.

The density will increase after the volumetric flask has been turned. It will therefore reduce in volume, but maintain its wt% content of KOH

  1. After this, you can rinse all equipment and the gloves with DI water in the sink, dry lightly with wipes, and let it dry in the KOH cabinet. Also rinse the inside of the fumehood with wipes with plenty of water.
  2. Clean the 1000mL plastic bottle with DI water and ethanol, and dry it properly with an N2 gun before you add your solution to the bottle. Let the solution cool a little before you tighten the lid.
  3. Label the flask with your name, activity number, contents, the date of preparation, sticker of the semester, and the GHS05 and GHS07 pictograms (corrosive and health hazards), and store it in the Base cabinet.

edited 09April2026 -Sindre Vie Jørgensen