Wiktionary
nitrosylsulfuric acid
n. (context inorganic compound English) A nitrosyl derivative of sulfuric acid that is used in industrial synthesis
Wikipedia
Nitrosylsulfuric acid
Nitrosylsulfuric acid is the chemical compound with the formula NOHSO. It is a colourless solid that is used industrially in the production of caprolactam, and was formerly part of the lead chamber process for producing sulfuric acid.