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Various definations of pH
A symbol for the degree of acidity or alkalinity of a solution.
Expressed as a negative logarithm of the hydrogen ion concentration
in a solution, pH = -log10[H+]. If the hydrogen ion concentration
of a solution increases, the pH will decrease, and vice versa.
The value for pure distilled water is regarded as neutral,
pH values from 0 to 7 indicate acidity, and from 7 to 14 indicate
alkalinity.
A term used to indicate the level of acidity or alkalinity
of pool water. Too low of pH causes etched plaster, metal
corrosion and eye irritation. Too high of pH causes scale
formation, poor chlorine efficiency and eye irritation. The
ideal range for pH in swimming pools is 7.4 to 7.6.
A measure of acidity and alkalinity of a solution that is
a number on a scale on which a value of 7 represents neutrality,
lower numbers indicate increasing acidity, and higher numbers
indicate increasing alkalinity. Each unit of change represents
a tenfold change in acidity or alkalinity and is the negative
logarithm of the effective hydrogen-ion concentration or hydrogen-ion
activity in gram equivalents per liter of the solution.
pH can be measured:
- by addition of a pH indicator into the studying solution.
The indicator color varies depending on the pH of the solution.
Using indicators, qualitative determinations can be made
with universal indicators that have broad color variablity
over a wide pH range and quantitative determinations can
be made using indicators that have strong color variablitiy
over a small pH range. Extremely precise measurements can
be made over a wide pH range using indicators that have
multiple equilibriums (ie H2I) in conjunction
with spectrophotometric methods to determine the relative
abundance of each ph dependant component that make up the
color of solution.
- by using a pH meter together with pH-selective electrodes
(pH glass electrode, hydrogen electrode, quinhydrone electrode
and other).
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