Chemistry Reference
In-Depth Information
Chapter 1
Introduction
1.1
Brief summary of methodologies
1.1.1
Titration method
The anions which can be determined by titration processes are listed below.
Non saline waters:
bicarbonate, bromide, carbonate, chlorate, chloride, hypochlorite, chlorite,
iodide, nitrate, nitrite, polysulphide, sulphate, sulphide, thiosulphate.
Sea water:
alkalinity, bromide, chloride, iodide and sulphate.
Surface, ground and
pore waters:
alkalinity and borate
Potable water:
alkalinity, chloride, chlorite, chlorate and hypochlorite.
Waste waters:
chloride, free cyanide, iodide.
Trade effluents:
chloride, free cyanide, polythionate, sulphate, sulphide and thiocyanate.
High purity water:
chloride and iodide.
Thus some 19 different anions can be determined in various types of water by this
technique. As titration procedures are relatively insensitive compared to some other
procedures, it is likely that they would only be applied to those types of water sample
where the concentration of the determinand is relatively high, eg sewage and trade
effluents and not, for example, to potable water samples.
The titration process has been automated so that batches of samples can be titrated
non-manually and the data processed and reported via printouts and screens. One such
instrument is the Metrohm 670 titroprocessor. This incorporates a built-in control unit
and sample changer so that up to nine samples can be automatically titrated. The 670
titroprocessor offers incremental titrations with variable or constant volume steps
(dynamic or monotonic titration). The measured value transfer in these titrations is either
drift controlled (equilibrium titration) or effected after a fixed waiting time; p
K
determinations and fixed end points (eg for specified standard procedures) are naturally
included. End-point titrations can also be carried out.
Sixteen freely programmable computational formulae with assignment of the
calculation parameters and units, mean-value calculations and arithmetic of one titration
to another (via common variables) are available. Results can be calculated without any
limitations.
The 670 titroprocessor can also be used to solve complex analytical tasks. In addition
