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p H - M E A S U R E M E N TBY MAHITHAp H - M E A S U R E M E N T It measures the acidity or alkalinity in a solution. pH is a measurement of hydrogen ion concentrationWhat is pH? Acid - increases the hydrogen ion (H+) concentration in a solution Base - increases the hydroxide ion (OH-) concentration in a solution pH is defined as the negative log of the molar concentration of dissolved hydrogen ions in aqueous solutionpH = - log [H+]pH Scale7140AcidBaseNeutralWhat is pH? p H Applications pH monitoring is essential to many applicationsChange in the chemical nature of a system will often be reflected by a change in pH pH monitoring is essential to many applicationsProcesses affected by pH Metal and gas solubility Corrosivity

Drinking water Wastewater Industrial water Environmental analysis

Coagulation and flocculation Biological activity

p H Applications HOW TO MEASURE p H? pHElectro Chemical MethodEx: pH Meter pH Indicator Ex: pH Paper , Indicator etc., Colorimetric MethodColor Comparison Ex: Color Discs or chart

p H Indicator Paper

- Paper strip chemically coated. Changes color according to acid or alkaline conditionsUsage:

Soak in solution for as long as recommendedCompare results with reference chart.

p H Color Comparator Fill two cells with sample

Add pH buffer/reagent to one sample cell

Insert both the cells in comparator boxRotate the disc to obtain color match

Read the pH through the scale window.Electro Chemical MethodElectro Chemical MethodElectro chemical measurement consists:

pH measuring Probe .Electronic Instrument to display the measured pH values.The most accurate pH measurementMethod.

Types:

Combined pH electrodeHalf cell Glass electrodeReference ElectrodeCombined pH electrode with in built temperature sensorpH Measuring Probe METERIon SensingHalf-CellReferenceHalf-CellAg/AgClWireInternal FillingSolutionReferenceElectrolyteSalt BridgeJunctionHalf Cell pH Electrode

Combined pH Electrode

CalibrationA calibration curve allows the meter to convert a measured millivolt potential into a pH reading.mVpHMeasurement - Special ConsiderationsLow ionic strength solutionsAbsorption of atmospheric carbon dioxide is a major source of driftLow ionic strength sample chamberCondition electrode in a solution of comparable ionic strength before use