Chlorides are salts resulting from the combination of the gas chlorine with a metal. Chlorine alone as Cl 2 is highly toxic and it is often used as a disinfectant. In combination with a metal such as sodium it becomes essential for life. Small amounts of chlorides are required for normal cell functions in plant and animal life. But excessive amounts of chlorides can also be harmful, such that it can corrode metals and affect the taste of food products. It can also contaminate freshwater streams and lakes. Some aquatic animals cannot survive in high levels of chlorides. By using chloride-selective electrode meters, concentrations of chlorides can already be measured accurately.