What chemical is commonly used as an oxygen scavenger in boiler water?

Sodium sulfite is widely recognized as an effective oxygen scavenger in boiler water management. It plays a crucial role in preventing corrosion within the boiler system. When introduced to water, sodium sulfite reacts with dissolved oxygen to form sodium sulfate. This reaction effectively removes the free oxygen that can lead to corrosion of metal components in the boiler, thus helping to maintain the integrity and longevity of the system.

In contrast, the other options do not serve as oxygen scavengers in the same capacity. Calcium carbonate primarily acts as a scale inhibitor and can help to stabilize pH levels but does not directly address dissolved oxygen. Magnesium hydroxide is typically used to control pH and may reduce corrosion but does not function specifically as an oxygen scavenger. Chlorine dioxide is primarily utilized for disinfection purposes and does not have the same role in managing dissolved oxygen levels in boiler systems. Therefore, sodium sulfite's specific chemical properties and reactions make it the most suitable choice for this application.