To raise the pH of boiler water, what should be added?

To raise the pH of boiler water, adding caustic soda (sodium hydroxide) is the preferred method. Caustic soda is a strong alkaline substance that increases the pH level of water, making it more alkaline. This is essential in boiler systems because a higher pH helps to minimize corrosion in the boiler and piping systems. Maintaining the correct pH balance is vital for the safe and efficient operation of boilers, as it prevents the formation of scale and protects against metal degradation.

In contrast, while calcium chloride, sodium bicarbonate, and magnesium sulfate have their applications in water treatment processes, they do not effectively raise the pH like caustic soda does. Calcium chloride is a salt that can potentially lower pH if not balanced correctly. Sodium bicarbonate acts as a buffer and may raise pH slightly, but not to the extent necessary for boiler operations. Magnesium sulfate is often used in other contexts and does not play a role in significantly altering the pH. Therefore, caustic soda is the correct choice for effectively raising the pH of boiler water.