The Cammidge reaction, also known as the Cammidge test, is a colorimetric chemical test used to detect and identify the presence of halogens, especially chlorine and bromine, in organic compounds. It is named after the English chemist Alexander Thomas Cameron Cammidge, who developed this sensitive and reliable test in the early 20th century.
In the Cammidge reaction, the organic compound to be tested is treated with a solution of sodium or potassium hydroxide and phenolphthalein. The mixture is then heated, and slowly added to a solution of sodium or potassium nitrite with acid, typically sulfuric acid. If halogens are present in the organic compound, they react with the nitrite compound and liberate nitrogen gas, while simultaneously producing a color change in the solution.
The color change is observed as a characteristic deep purple or violet color, indicating the positive presence of halogens. This color change occurs due to the formation of an azo compound, which is intensely colored. The intensity of the color produced is directly proportional to the amount of halogens present in the organic compound.
The Cammidge reaction is widely used in organic chemistry laboratories for the qualitative detection of halogens, particularly in aromatic compounds. It is a valuable tool for preliminary analysis, identification, and differentiation of organic compounds containing halogens, and it provides reliable results in a relatively short period of time.
