Brigadier General Carl Rogers Darnall discovered the value of using compressed liquefied chlorine gas to purify water for use by troops in the field. His invention in 1910 of mechanical liquid chlorine purifier (chlorinator) is now used throughout the world. This monumental discovery was later applied to municipal water supplies. It is impossible to estimate the influence that a pure water supply has had on public health. It is safe to say that more lives have been saved and more sickness prevented by Darnall's contribution to sanitary water than by any other single achievement in medicine.
Born on his father's farm in the Cottage Hill community near McKinney, in Collin County, Texas, on Christmas Day 1867, Carl Darnall was the eldest of the seven children of Reverend Joseph Rogers Darnall, minister of the Christian Church, and Mary Ellen (Thomas) Darnall. He attended the Carlton College in Bonham, Texas, and graduated from Transylvania University, Kentucky, and Jefferson Medical College in Philadelphia, Pennsylvania, where he received his medical degree in 1890. After a few years of private practice, Dr. Darnall entered the military service as an assistant surgeon in 1896. He was commissioned in the Army Medical Corps, and his first assignments were to stations in Texas Fort Clark at Brackettville, and Fort McIntosh at Laredo.
During the Spanish-American War, Darnall served in Cuba. Later, he served as an operating surgeon and pathologist aboard the hospital ship Relief in the Philippines and commanded the hospital at Iloilo. He was one of the few medical officers that accompanied the Allied Forces during the Boxer Rebellion in China.
In 1902, he returned to Washington, D.C., and served as secretary of the faculty and instructor for sanitary chemistry and operative surgery at the Army Medical School. It was while professor of chemistry that he discovered the value of liquid chlorine in purifying water. Darnall also devised and patented a water filter that was used by the Army for many years.
During World War I, Lieutenant Colonel Darnall's talents for business and organization were recognized and he was assigned to the Finance and Supply Division in the Office of The Surgeon General. After the war, he served as department surgeon in Hawaii.
In 1925, he returned to the Office of The Surgeon General as executive officer. In November 1929, he was promoted to brigadier general and became the Commanding General of the Army Medical Center. He held this post until he retired in 1931.
Darnall died January 18, 1941. Six days earlier, his devoted wife, Annie Estella, died at the family home in Washington. He left three sons, Joseph Rogers, William Major, and Carl Robert, all of who served in some capacity in the Army.
General Darnall was the author of a number of papers on professional subjects in chemistry and surgery. He was a Fellow of the American College of Surgeons, a member of the American Medical Association, and a member of the Association of Military Surgeons of the United States. He was a veteran of the Military Order of the Carabao, member of the Army and Navy Club of Washington, and Founder Member of the Army and Navy Country Club. Darnall received the Distinguished Service Medal for his organizing, developing and administering medical supplies in World War I.