Luckau Protocols:KCl

KCl Protocol

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Purpose

In the Clark Lab, 3M KCl is used as a storage solution for the pH meter electrode. In the Clark Lab, 5M KCl is used as a stock solution for making the PCR Buffer series (A through H)

Info

• Potassium chloride, KCl (anhydrous)
  • we currently use Sigma-Aldrich, catalog P-9541, Lot 34H030215
• FW = 74.55 g/mol

To make 125 mL of 3M KCl

Calculations

• [math]\displaystyle{ 125 \mathrm{mL} \bullet \tfrac{3 \mathrm{mol}}{\mathrm{L}}\ \bullet \tfrac{\mathrm{L}}{1000 \mathrm{mL}}\ \bullet \tfrac{74.55 \mathrm{g}}{\mathrm{mol}}\ = 27.96 \mathrm{g} }[/math]

Protocol

1. Using digital scale, place 27.96 g KCl powder into weigh boat
2. In 150 mL flask, mix 27.96 g KCl with 100 mL H₂O
3. Put flask on hotplate with stirbar until dissolved
4. Add H₂O to bring volume to 125 mL

• If this 3M KCl is being used for the storage solution for the pH meter electrode, then leave the solution in the Erlenmeyer flask, insert electrode, then wrap with parafilm as best you can to prevent evaporation.

To make 200 mL of 5M KCl

Calculations

• [math]\displaystyle{ 200 \mathrm{mL} \bullet \tfrac{5 \mathrm{mol}}{\mathrm{L}}\ \bullet \tfrac{\mathrm{L}}{1000 \mathrm{mL}}\ \bullet \tfrac{74.55 \mathrm{g}}{\mathrm{mol}}\ = 74.55 \mathrm{g} }[/math]

Protocol

1. Using digital scale, place 74.55 g KCl powder into weigh boat
2. In 250 mL beaker, mix 74.55 g KCl with approximately 175 mL H₂O
3. Put flask on hotplate with stir bar until dissolved

note: this concentration seems to be at the limit of KCl's solubility, so it may require a good amount of heat (~60°C) as well as plenty of time (~1 hour) to dissolve completely

1. Add H₂O to bring volume to 200 mL

• If this 5M KCl is being used as the stock solution for PCR Buffers A-H, then transfer to a 250 mL glass media bottle and store at room temperature on the chemical shelf.