By products in the water resulting from the use of any chlorine product. Principal component of Total Dissolved Solids

Both calcium and magnesium chlorides are found in boiler feed water, the magnesium chloride being particularly undesirable, as it breaks down, when heated to boiler temperature, probably forming magnesia and hydrochloric acid, thus producing corrosion, Calcium and magnesium chlorides are converted to insoluble salts by the same reagents ordinarily employed to treat sulphates.

a compound of chlorine with another element, especially a salt or ester of hydrochloric acid.