Water quality is an important issue, noting that normal tap water has different
ionic content, although thought to be pure by many.
In this experiment, the intent is on
testing the ionic contents and concentrations of tap water obtained from sinks in several
different locations throughout Tucson.
Four different tap water samples located
throughout Tucson will be measured for ionic content.
Two samples of tap water will be
collected from different areas located on the University of Arizona campus (Well #4) to
compare and contrast the ionic content for a similar location.
The other two samples will
be obtained from the eastside of Tucson (Well #6) and the westside of Tucson (Well #3).
This experiment deals with determining the quality of water by using the techniques of
complexometric titration, ion exchange chromatography, potentiometry and flame
This experiment is intended to determine the total divalent metal ion
concentration using a complexometric titration, to determine the total ionic content using
ion exchange chromatography, to determine the [Ca
] using an ion selective electrode,
and to evaluate a series of samples for ionic content.
Complexometric titration is a volumetric technique for determining the amount of
a particular material present in a sample.
It is commonly used to measure the number of
metal cations present in a solution, as well as to determine “water hardness”, which is a
measure of the amount of divalent metal cations, primarily Ca
present in the
The higher the concentration of these ions, the harder the water is considered to
The technique of complexometric titration will allow the determination of total
divalent and trivalent metal ion contents, as well as the molarity of Ca
case, the trivalent metal ions were assumed to be none and were, therefore, not assessed.
This technique involves a common complexing agent, ethylenediaminetetraacetic acid,
EDTA, which will be diluted to 3 different concentrations.
For each titration trial, the
concentration of divalent metal cations as both molarity and as parts-per-million (ppm)
will be determined.
The concentration of [M
] can be determined by the following
] = moles M
/sample volume, where moles M
= moles EDTA used.
parts-per-million (water hardness) can be determined by the following equation: ppm =
mass of component/mass of sample x 10
, where all divalent ions are assumed to be
calcium ions, therefore assumed there were trivalent cations present, and the
concentration of divalent cation is converted according to the equation units (Brown,
An indicator is used throughout this experiment which forms a complex that has a
different color than the free ion, allowing the chemical change to be visibly determined
This indicator is Eriochrome Black T (ErioT), a triprotic acid.
content, pH, dissolved acids, organics, and water hardness are common measures of