Formaldehyde-saturated heptane
MATERIALS
Equipment
Aluminum foil
Scintillation vial or 100-mL glass bottle with plastic screw top (see Step 1)
METHOD
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1. Combine equal volumes of heptane and 37% formaldehyde. Use a scintillation vial for small volumes (2-10 mL); use a 100-mL glass bottle with a plastic screw top for larger volumes (25-80 mL).
See Troubleshooting.
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2. Secure the lid. Shake the mixture vigorously for 15 sec. Let the solution settle into two phases.
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3. Repeat this mixing procedure several (at least three) times before using the solution to ensure that the heptane becomes saturated with the formaldehyde.
It is best to prepare formaldehyde-saturated heptane on the day before it is to be used, shaking the vial or bottle periodically throughout the day. The saturated heptane is the upper phase in the 1:1 heptane:formaldehyde stock.
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4. Because formaldehyde is sensitive to light, wrap the container in aluminum foil.
Stored at room temperature, the mixture remains active for several months.
TROUBLESHOOTING
Problem: Crystals form in the mixture upon addition of the formaldehyde.
[Step 1]
Solution: The solution will not work properly and should be discarded. Use formaldehyde from another source to prepare fresh solution.
