2013: Advent Chemistry: Dropwise

by on December 15, 2013
Drip. Drip. Drip.

Drip. Drip. Drip.

Sometimes – often – there are no shortcuts. If you wan to get the best results, you have to take time over them. You have to let your mixture reflux for long enough. You have to dry it off in the oven until it’s properly dry. And when the recipe calls for dropwise addition, that’s what you have to do.

“Dropwise” means exactly that: drop by drop. There are two usual reasons you might need to be that slow and gradual, the first of which is yield. It’s generally the goal to produce as much product as possible from your starting ingredients, and adding one reactant very slowly to the other, while stirring or heating or both, often helps.

The second reason is slightly less obvious. Heat. Exothermic reactions can’t always be kept safe and under control just by icing down the mixture, particularly if they need to be above a certain temperature to start reacting. To keep the heat they produce in check, you resort to a more direct control method, and slow down the reaction. Reduce how much reaction can happen at once, and you reduce how much heat it can produce.

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