Whats the history/background on the pH Scale
http://www.corrosion-club.com/historypHscale.htm
The pH scale is a measure of the acidity or alkalinity (basicity) of a solution. It was invented by the Danish biochemist Søren Peder Lauritz Sørensen in 1909. The acronym "pH" stands for "potential of Hydrogen."
To understand the history and background of the pH scale, we must start with the concept of acidity. The idea of acidity dates back thousands of years, with ancient civilizations recognizing certain substances as sour-tasting. However, it wasn't until the late 18th century that a French chemist named Antoine Lavoisier proposed the theory of acidity as the presence of oxygen in a substance.
In the early 19th century, Swedish chemist Jöns Jacob Berzelius introduced the term "catalysis" and described certain substances as either acidic or basic. However, there was no quantitative scale to measure acidity until the late 19th century when various researchers began developing different methods.
It was Sørensen who introduced the concept of pH as a measurement of acidity. He needed a way to measure the activity (concentration) of hydrogen ions (H+) in a solution accurately. Sørensen recognized that existing methods were inadequate, such as using litmus paper, which only indicated if a solution was acidic or basic.
Sørensen devised a logarithmic scale to measure hydrogen ions' concentration, making it easier to work with a wide range of concentrations. He defined pH as the negative logarithm (base 10) of the activity of hydrogen ions in a solution. This scale ranged from 0 to 14, with 7 being neutral, values less than 7 indicating acidity, and values greater than 7 indicating alkalinity.
Initially, Sørensen's pH scale was focused on the relationship between acidity and the ion concentration of hydrogen. However, over time, the definition shifted to focus on the concentration of hydrogen ions directly, making it easier to measure and understand.
Since its development, the pH scale has been widely adopted and used in various fields, including chemistry, biology, environmental science, medicine, and agriculture. It has become a fundamental concept in understanding the properties of solutions and their impact on living organisms.
To measure pH today, a pH meter or pH indicator (such as litmus paper) is typically used. These tools determine the concentration of hydrogen ions in a solution, allowing us to classify it as acidic, basic, or neutral on the pH scale.