If you get chemicals, from iodine to detergents, in the form of tiny little pellets, chances are they have been "prilled." What's prilling? Think about what this strange process could be. And whatever you're thinking, it's even simpler than that.

If you look through a catalog of chemicals you'll find that some substances come in different forms. You can get flakes, or a solution at a certain concentration, or you can get your chemicals "prilled." Prilled chemicals come in little beads. Usually each bead is roughly the size of a pinhead and remarkably spherical. Urea and iodine come this way, but so do some household products like detergents. How do they make so many tiny little balls, so evenly sized?


The answer is almost too simple. They melt the chemical down, and drop tiny droplets of it off a tower. On its way to the ground, each droplet naturally forms a spherical ball, and then freezes as the air cools and dries it. By the time it has hit the ground (or a vat of cool liquid) it has been "prilled." The fact that prilling resembles something that Willy Wonka would do doesn't make it any less effective.

I would still like to see a prilling tower sometimes. I wish they would do it with chocolate.

Image: LH Chem

[Source: The Culture of Chemistry, Prilling.]