Adsorbent

Part of speech: adjective, noun

Definitions

1. A substance that has the capacity to collect particles on its outer layer while not integrating them fully into its mass
2. A material capable of attracting and holding particles or molecules on its exterior without absorbing them internally
3. A compound that collects and retains substances on its surface by physical or chemical means rather than absorbing them

Etymology: Heinrich Kayser, a German physicist, needed a term for a process that "absorb" did not describe. Gases were clinging to the surface of charcoal rather than soaking into its interior, and "absorb" implied the whole body taking the substance in. He built a new word from Latin "ad-", meaning "to" or "toward", and "sorbere", meaning "to suck in" or "swallow." The pair is instructive. "Absorb" combines "ab-" ("away," here meaning completely) with the same root, so absorbing draws material into the interior, while adsorbing holds it on the outside. The ending "-ent" comes from the Latin present participle, the same suffix found in "agent" and "student." That is why the term works as both a description of a process and a name for the material that carries it out.

Synonyms: absorptive, adhesive, sticky, clingy, sorbent