Nitroso R Salt is primarily used as a reagent in analytical chemistry for the detection and determination of metal ions, particularly cobalt and other heavy metals like iron. It forms colored complexes with these metals, which can be measured spectrophotometrically to quantify their concentrations in industrial, environmental, and research samples. This is especially valuable in environmental testing for monitoring pollution in water and soil, and in metallurgical industries for alloy composition analysis and quality control. Additionally, it is employed in the production of azo dyes and serves as an intermediate in the synthesis of other organic chemicals in the chemical industry. Its selective binding properties make it a versatile tool in both analytical and synthetic applications.