nonhydrogen

Nonhydrogen is a term used in chemistry and related disciplines to refer to substances, elements, or compounds that do not contain hydrogen atoms. In practice, it is often used to contrast with hydrogen-containing species such as water, hydrocarbons, or alcohols. The concept can apply to pure elements, simple inorganic compounds, or complex mixtures where hydrogen is absent or negligible.

Examples and scope include noble gases (helium, neon, argon), many metal elements, and inorganic compounds such as carbon dioxide, carbon monoxide, silicon dioxide, sodium chloride, and sulfur trioxide. In materials contexts, analysts may describe the nonhydrogen fraction of a sample, either after dehydrogenation or as part of compositional analysis. The term is also used in astrophysics and plasma physics to describe environments where hydrogen is not the dominant constituent.

Limitations and usage: The term is informal and its exact meaning depends on context. It is not a strict chemical classification, and some discussions may treat hydrogen content as negligible rather than strictly zero. In formal nomenclature, more explicit language such as "hydrogen-free" or "hydrogen-containing" is often preferred to avoid ambiguity.