Trans Recording Solution

• 1. Weigh out 4.19 g of Ba(OH)₂ dry powder to produce a final concentration of 53 mm Ba²⁺. (Ba(OH)₂ is very hydroscopic, so protect it from exposure to air and purchase a new lot periodically.)

• 2. Add 14 g of HEPES dry powder. Add water to yield a final volume of 250 mL. Stir until the powder dissolves.

• 3. Measure the pH. Keep adding dry HEPES with stirring until the pH reaches 7.35.

• 4. Record the final amount of HEPES added. (The total amount of HEPES should be in the range of 14–16 g, yielding a final HEPES concentration of 235–260 mm.)

• 5. Filter the solution to remove precipitate.

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