After the addition of reagents for the nitrate test, the tube remains colorless. To determine if the organism reduced nitrates to nitrogen gas, you must now add

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When a nitrate test remains colorless after the addition of reagents, zinc dust is added to determine if the organism reduced nitrates to nitrogen gas. If the solution remains colorless after adding zinc, it indicates that nitrate was reduced to nitrogen gas or other non-detectable forms, as zinc would have reduced any remaining nitrate to nitrite, causing a color change if nitrate was still present.

After the Addition of Reagents for the Nitrate Test, the Tube