Diammonium Phosphate
Diammonium Phosphate is a salt used to invigorate yeast and add vital nutrients to yeast starters and wines; such as wines and meads. Today often used to prevent the build up of carbonic acid in hard seltzer.
The chemical formula for Diammonium Phosphate is (NH4)2HPO4).
To use: add between 1/2 to 3/4 grams per gallon.