🔍 Key Concepts

• Boiler water chemistry and why oxygen in the water is a problem • What sulfite (or sodium sulfite) is added to boiler water to do chemically • Difference between scale-forming salts (nitrates, sulfates, phosphates) and oxygen scavenging agents

💭 Think About

• Ask yourself: in boiler treatment, what specific job does sulfite perform—does it form scale, condition sludge, or react with dissolved gases? • Which choice mentions something that is not a solid impurity but instead relates to how much chemical treatment is present? • Think about what test you would use to know if you still have enough chemical on board to keep removing dissolved oxygen from the boiler water.

✅ Before You Answer

• Verify which of the listed items (nitrates, sulfates, phosphates, excess oxygen scavenging agents) are scale-forming salts versus treatment chemicals. • Check your engineering knowledge: sulfite reacts directly with dissolved oxygen—so what would a test for sulfite indirectly tell you about? • Confirm that the test name usually matches the treatment chemical being measured, not the contaminant itself among the answer choices.