chlorine37

Chlorine-37 is a stable isotope of the chemical element chlorine. It has a mass number of 37 and, together with chlorine-35, makes up the natural isotopic composition of chlorine found in Earth's environment. The two stable isotopes are present in roughly 75.8% and 24.2% abundance, respectively, with chlorine-35 being the more abundant.

In terms of nuclear composition, chlorine-37 contains 17 protons and 20 neutrons. Like other stable isotopes of chlorine, it does not undergo radioactive decay under normal conditions and forms the same chemical species as chlorine-35, including molecular chlorides in salts and organic compounds. The presence of two stable isotopes gives rise to natural isotopic variation that can be measured with precision instruments.

The ratio of chlorine-37 to chlorine-35 in natural chlorine is about 0.32, meaning there are roughly 0.32 parts of Cl-37 for every part of Cl-35. This isotopic ratio can be measured accurately using isotope-ratio mass spectrometry and is used in geochemical, hydrological, and environmental studies to trace chlorine sources, track processes that fractionate isotopes, and understand past climatic and ecological conditions.

Applications of Cl-37 measurements include provenance studies of chloride in seawater, rivers, and atmospheric deposition, as well as studies of mineralogy and soil chemistry. Because chlorine-37 is stable, it serves as a reliable marker in tracer and isotopic investigations without the complications of radioactive decay.