75 % phosphoric acid E338.
Can be used to lower the mash pH and lauter pH. Does not affect the Chloride/Sulphate ration. Use pH test strips or a pH meter to check the actual pH of the mash.
May also be used for yeast washing to kill off weak yeast cells and unwanted bacteria in the yeast slurry. Also used as a flavouring for soft drinks.
Safety data sheet (PDF)