Last week, I came across an advertisement for Chlorine Gas, marketing it as a “new scientific discovery for the prevention and elimination of colds” and further boasting that it is “now obtainable at drug stores.” The Indianapolis Star ad from March 1926 fell into a brief period where the incredibly dangerous gas was marketed as “Resprine” and prescribed by doctors. While chlorine gas will generally kill viruses and bacteria, it also has a habit of killing pretty much every form of life. There are a few bacteria, spores, and parasites that are resistant to its effects, but they are the excepti...