1. Look in Durham Tube for nitrogen gas (a bubble at top) - if no gas, go to step 2
2. Look for nitrite. Add reagents A & B. If nitrite is present, a red ring forms at the top of the tube. If no red ring, the organism either could not convert nitrate into nitrite, or it converted into NO or NH4.
3. Add Zinc (catalyst) - it catalyzes the conversion of nitrate to nitrite. If red precipitate forms, NEGATIVE result b/c you made the conversion, not the bacteria!
4. If no red precipitate formed, the organism converted to either nitric oxide or ammonia. Smell it to see if it smells like ammonia.