Chapter 3
System of Units
3.1 The Value of Defined Quantity Is the Quantity
Expressed as the Product of Number and Unit
of Measurement
Information about the environment is obtained through the measurement of various
quantities, for example, physical and chemical. These quantities allow characterization of the properties of objects (samples), phenomena or processes. Such properties
can be determined qualitatively and quantitatively. They can also be compared qualitatively and quantitatively with the same properties of other objects or phenomena.
The term ‘quantity’ means the amount in a general sense (length, time, mass, concentration) or a specific value (length of the rod, the weight of the weight, the journey
time, the concentration of sodium ions in the mineral water). Measurement as such
is an experimental activity, aiming to determine the value of the quantity expressed
as a number and unit of measurement.
Measurement unit: real scalar quantity, defined and adopted by convention,
with which any other quantity of the same kind can be compared to express
the ratio of the two quantities as a number. [clause 1.9; ISO/IEC Guide 99]
System of units: a set of base units and derived units, together with their
multiples and submultiples, defined in accordance with given rules, for a given
system of quantities.
[clause 1.13; ISO/IEC Guide 99]
Hence, metrology can be considered as a scientific discipline dealing with setting
the dimensions of the measured quantities and their units as well as methods of
measuring.
Quantities used to characterize the properties of the objects are divided into base
and derived quantities. Base quantities are those that in a given unit system are
© Springer Nature Switzerland AG 2018
E. Bulska, Metrology in Chemistry, Lecture Notes in Chemistry 101,
https://doi.org/10.1007/978-3-319-99206-8_3
23
System of Units
3.1 The Value of Defined Quantity Is the Quantity
Expressed as the Product of Number and Unit
of Measurement
Information about the environment is obtained through the measurement of various
quantities, for example, physical and chemical. These quantities allow characterization of the properties of objects (samples), phenomena or processes. Such properties
can be determined qualitatively and quantitatively. They can also be compared qualitatively and quantitatively with the same properties of other objects or phenomena.
The term ‘quantity’ means the amount in a general sense (length, time, mass, concentration) or a specific value (length of the rod, the weight of the weight, the journey
time, the concentration of sodium ions in the mineral water). Measurement as such
is an experimental activity, aiming to determine the value of the quantity expressed
as a number and unit of measurement.
Measurement unit: real scalar quantity, defined and adopted by convention,
with which any other quantity of the same kind can be compared to express
the ratio of the two quantities as a number. [clause 1.9; ISO/IEC Guide 99]
System of units: a set of base units and derived units, together with their
multiples and submultiples, defined in accordance with given rules, for a given
system of quantities.
[clause 1.13; ISO/IEC Guide 99]
Hence, metrology can be considered as a scientific discipline dealing with setting
the dimensions of the measured quantities and their units as well as methods of
measuring.
Quantities used to characterize the properties of the objects are divided into base
and derived quantities. Base quantities are those that in a given unit system are
© Springer Nature Switzerland AG 2018
E. Bulska, Metrology in Chemistry, Lecture Notes in Chemistry 101,
https://doi.org/10.1007/978-3-319-99206-8_3
23