Used primarily as a nitrosating agent in organic synthesis, enabling the introduction of nitroso groups into aromatic and aliphatic compounds. Commonly applied in the preparation of diazonium salts and azo dyes. Also serves in the synthesis of nitrosamines for research purposes. Its strong electrophilic nature makes it effective in catalyzing certain oxidation reactions and in the modification of heterocyclic compounds. Handle with care due to its reactivity and potential decomposition releasing toxic gases.