CaSO4 (Anhydrous molar weight 136.14) is used by advanced brewers to improve the wort chemistry as burton salts. Sulphates improve the hoppiness and Calcium gives hardness for dark beers. Details on dosge here. Please use the packet sparingly few gm per batch is all you need.
This is extra pure salt for brewing purpose. Unlike commercial salts, here Arsenic is 0.005% and lead 0.005% Zinc and Iron are also less than 0.001%