ABSTRACT
Weights and measures are defined by the agreed Systeme International and are usually referred to as SI units. The units one will most likely meet in a biological laboratory are mass in grams (g), volume in litres (l), amount of substance in moles (mol) and molar concentrations (M). The metric system uses multiples of 10 to express decimals. This chapter presents the multiplication factor, prefix and symbol for the full range. Chemicals used for biological and physiological research are usually at very low concentrations in the lower milli (m) and micro (p) areas. However Undergraduate and postgraduate students of science, medicine and biomedical science should be familiar with the other terms. They may find it useful to practise converting from an exponential multiplication factor to a prefix and symbol, as both ways of expressing concentration are routinely used. Reagents are often prepared as a concentrated stock that has to be diluted before use.
