The production of results

Every analysis is undertaken for a reason and the results of the analysis should be presented in an unambiguous manner to enable valid conclusions to be drawn. There are certain aspects of reporting analytical results which should be considered. 

Confused and inconsistent use of units of measurement often presents problems and in 1960 the Systeme International d Unites (SI units) was introduced. This aimed to produce a universal system of units in which only one unit was used for any physical quantity. It also provides coherence between appropriate measurements and minimizes the number of multiples and sub-multiples in use. 

The system defines seven base units (Table 1.7), which are independent of each other but which can be combined in various ways to provide a range of derived units (Table 1.8), each one capable of describing a physical quantity. Coherence is maintained in these derived units because no conversion factors are involved at this stage but in order to provide units of convenient size for different applications a series of standard prefixes may be used. These are multipliers used with coherent units to obtain units of alternative size but only one prefix should be used at a time (Table 1.9). 

Physical quantity Derived unit Symbol Name 

Force Kilogram metre per second per second kg m s-2 Newton 

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