last updated Wed, Apr 6, 2005

General

Check for the concentration of common acids and bases.

Experiments

1. Step 2 (Work-up)

"36% HCl" refers to concentrated hydrochloric acid. There is nothing such as 100% HCl! See link above.

In some instances, the reaction turns green in color and a phase separation is observed upon standing. It is highly advisable to repeat the experiment in such an event. Most likely, some of the methanol evaporated away, probably causing the phase separation. Keep in mind that the majority of the formaldehyde solution is water.

The extraction can be performed in one batch since the suspension after addition of the water does not fit entirely into the 125 mL separatory funnel. How much solvent is appropriate here to use for extraction? (Hint: see chapter about "Extraction Theory" in appendix of your reader)

The organic layer should be extracted once with water before treated with saturated sodium chloride solution and drying it over Na₂SO₄. This step permits to remove more of the unreacted formaldehyde from the organic layer.

The removal of the solvent should be aided by applying an air stream.

The recrystallization step takes some time in any cases. Make sure that you dissolve the crude product and then place it in an Erlenmeyer flask, which is closed with parafilm.