5. Quantities, Units and Symbols

The 'Green Book' [ref. 3] provides an up-to-date account of IUPAC requirements in these areas. An abbreviated list is also available [ref. 4]. During the writing of the 'Green Book', careful harmonization was made with analogous recommendations from ISO and from the International Union of Pure and Applied Physics (IUPAP).

Certain rules in the 'Green Book' must be strictly adhered to, namely, the italic letters for symbols for physical quantities and roman letters for units (section 1.6), and the instructions for the printing of numbers and mathematical symbols (section 4.1). These points are highlighted below.

When a document includes recommendations for a number of new quantities and symbols, as may often happen in dealing with a specialized area of chemistry, it will generally be helpful to provide a summary table of all quantities included in the document, similar to the tables in Chapter 2 of the 'Green Book', with the headings: Name, Symbol, Brief defining equation, SI Unit, Notes. Tables of this kind allow the reader to recover important information quickly when referring to a document for the second or third time, and allow easy comparison between different documents.

The specific use of quantities and units in Clinical Chemistry is discussed in refs. 40 and 41.