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If it does get very brown and cloudy, add a bit more vinegar and boil again.

The sodium acetate starts out as "sodium acetate trihydrate," meaning it contains water. Once all the water around it is gone, those water molecules start to evaporate and the sodium acetate becomes "sodium acetate anhydrous," meaning "without water."

Vinegar is mostly water, which you'll need to boil away. Once about 90% of the liquid is gone — which could take half an hour of boiling or more — a crusty film will begin to form on the surface.This means all the excess water is gone and you need to turn off the heat as fast as possible. If you let too much of a crust develop, your liquid will get cloudy and not work very well.