Simmons’ citrate agar was developed by James S. Simmons in 1926 by adding 1.5% agar and bromothymol blue as a pH indicator to Koser’s citrate agar to observe changes in pH as a result of oxidative reactions from citrate metabolism.
In 1926, James S. Simmons developed Simmons' citrate agar by incorporating 1.5% agar and bromothymol blue into Koser's citrate agar as a pH indicator to monitor changes in pH caused by the metabolic activity of citrate.