pH

History and Development of pH Measurement

• Danish chemist Søren Peter Lauritz Sørensen introduced the pH concept in 1909 at Carlsberg Laboratory.
• Sørensen revised the notation to the modern pH in 1924 for electrochemical measurements.
• Bacteriologist Alice Catherine Evans is credited for the development of pH measuring methods.
• Arnold Orville Beckman invented the first electronic pH measuring method in 1934.

Definition and Scale of pH

• pH is defined as the decimal logarithm of the reciprocal of hydrogen ion activity.
• The pH scale is logarithmic, indicating acidity or basicity of solutions.
• The pH range is commonly given as 0 to 14, with values below 7 being acidic, above 7 being basic, and 7 being neutral.
• The pH scale is traceable to standard solutions by international agreement.

Applications and Importance of pH Measurement

• pH measurements are crucial in chemistry, agronomy, medicine, and water treatment.
• pH influences bacterial growth, food safety, and various industrial and laboratory processes.
• pH of aqueous solutions is measured using a glass electrode and pH meter.
• pH measurements are important for understanding and controlling various processes.

pH Measurement Techniques and Challenges

• pH can be measured as the logarithm of hydrogen ion concentration using the Nernst equation.
• Glass electrodes are commonly used for practical pH measurements.
• Calibration against buffer solutions is proposed by IUPAC.
• Challenges include difficulties in extreme pH conditions and the need for specialized electrodes.

pH in Various Environments and Fields

• Soil pH ranges from ultra-acidic to hyper-alkaline and is influenced by various factors.
• pH in plants affects pigments and enzyme activity.
• Ocean acidification is a result of carbon dioxide emissions, causing a decrease in ocean pH.
• Blood pH is usually slightly basic, with acidosis and alkalosis indicating imbalances in the body.
• pH calculations are crucial in chemical speciation, weak acid-base reactions, and equilibrium constants.

pH Data Sources