CORRELATIVE INDEXES IV: CORRELATIVE CHEMICAL-GROUP INDEXES.

The article states that for many years chemists have had devices for precisely communicating information about individual chemical compounds. The structural formula and the molecular model are two of the more effective devices for precisely and rapidly communicating most of the important structural information about individual chemical compounds. An example of a structural formula is that of the compound 1-iodo-4-nitrobenzene. An example of a molecular model (in two dimensions) is that of methane, CH4.