EDTA: Ethylenediamine with Sodium Chloroacetate and Soda at 90-95 C, Precipitated with Hydrochloric Acid (Munz, US 2,130,505)

Each of the four hydrogens on the two nitrogens of ethylenediamine can take an acetic-acid arm from chloroacetate. Munz heated the amine with four shares of sodium chloroacetate and soda to soak up the acid set free; acidified, the four-armed acid falls out because it hardly dissolves in water. Its salts became the standard way to grip calcium and magnesium. Result: ethylenediaminetetraacetic acid (EDTA), the free acid. Source: Munz, US 2,130,505 (General Aniline, 1938). Not given: yield. Picture drawn by Youblob.