Name: ammonium glycyrrhizinate Molecular Formula:C42H62O16.2(NH3) Molecular Weight:857.00 CAS Registry Number:79165-06-3 "Ammonium" is also an old name for the Siwa Oasis in western Egypt. The ammonium cation (also known as ionized ammonia due to its electrical charge) is a positively charged polyatomic cation of the chemical formula NH+4. It has a formula weight of 18.05 and is formed by the protonation of ammonia (NH3). The resulting ion has a pKa of 9.25. Ammonium and aminium are also general names for positively charged or protonated substituted amines and quaternary ammonium cations N+R4, where one or more hydrogen atoms are replaced by organic radical groups (indicated by R).