| ̷ ̷ ̷ ̷+ noun
Etymology: International Scientific Vocabulary phenyl + hydrazine; originally formed as German phenylhydrazin
: a toxic liquid nitrogen base C 6 H 5 NHNH 2 that is made by reduction of benzenediazonium chloride and that reacts with aldehydes, ketones, acids, and related compounds to form hydrazides, hydrazones, and osazones useful in the identification of such compounds especially as sugars