Sodium not Postassium, people.

Every chemistry grad student knows a story about a fire started from a solvent still. Every time we hear a story we are reminded just how dangerous stills are, despite their ubiquity in synthetic labs. Until today, I have only known people who have been lucky.

I returned to my office this morning to find James, sitting at my desk waiting for me, totally white in the face. He had just seen a girl come running down the hall in her underwear completely black. She got under the safety shower and then turned red from the first degree burns covering much of her body including her face.

For those of you who have no idea what a still is, imagine about three liters of organic solvent (think gasoline or turpentine) that you have in a funky giant piece of glassware. Often you add chunks of sodium or potassium that react with any trace water in the solvent. Stills to prepare dry solvents are necessary for reactions that are sensitive to even the tiniest amounts of water. In the modern scientific world, this means most synthetic chemistry. Usually the danger is when you are trying to get rid of a still, or “kill” it. Safely reacting away any extra sodium or potassium has to be done with real care since you can easily ignite the liters of solvent.

It seems she had done everything right: killing the still first with isopropyl alcohol, then methanol and finally water. But if you have a potassium based still, the reaction with water is very violent and if there is any left, you will ignite the solvents. This is what happened upstairs today.

Here is the lesson for the day: use sodium, not potassium. The reaction is less vigorous with water. And make sure you toss a big stir bar in and stir all of the white stuff up to make sure there is nothing left before you do the final water step.

This is your safety lecture for today. Play safe.