All chemical substances or their mixes destined for laboratory work, mostly for chemical analyses, are commonly called chemical reagents. 

Characteristic features of the reagents: 

Unequivocally defined and guaranteed quality parameters of substances, determining both content of the main constituent and admissible level of contamination, determined shelf life, method of packaging appropriate for laboratory use, packages that provide stability of substance constitution during storing.

Chemical reagents, except for the main application in chemical analysis, are also used to perform scientific and research works, for preparation works and as raw materials for manufacturing other substances on a small scale. 

As regards quality, chemical reagents are divided to: 
pure reagents for analysis (pure for analysis, PA) - this is the basic group of reagents of quality level selected optimally to perform chemical analyses. They are more versatile as regards application in everyday work in laboratory, 
pure reagents (pure) - in relation to reagents of "analytically pure" class, they are of lower guaranteed quality parameters. In laboratory applications, they are used as auxiliary substances or as substrates for syntheses, 
special purpose reagents - characteristic feature of these reagents is their specialised purpose. Their guaranteed quality parameters were selected from the point of view of application for accurately specified types of analyses or analytical techniques.