Alkalinity

Introduction

The alkalinity of water is a measure of how much acid it can neutralize. If any changes are made to the water that could raise or lower the pH value, alkalinity acts as a buffer, protecting the water and its life forms from sudden shifts in pH. This ability to neutralize acid, or H⁺ ions, is particularly important in regions affected by acid rain.

When acid rain falls on a lake having low alkalinity, it is not neutralized, so the pH of the water decreases. This drop in the pH level can harm or even kill some of the aquatic organisms in the lake. When acid rain falls on a lake having high alkalinity, the acid is partially neutralized and the pH of the water remains fairly constant. In this way, a high alkalinity level helps maintain the health of the water and the organisms that live there.

Alkalinity should not be confused with pH. The pH of a solution is a measure of the concentration of acid, or H⁺ ions, in the water. Alkalinity is a measure of the water’s capacity to neutralize an acid, or H⁺ ions, thereby keeping the pH at a fairly constant level.

Objectives

• Measure alkalinity of a stream or lake by titrating with sulfuric acid.