Experiment No. 49
Testing for Nitrites in Water
To 50 cc. of water in a small beaker add with a pipette 2 cc. of naphthylamine hydrochloride and then 2 cc. of sulphanilic acid. Stir well and wait 20 minutes for color to develop. A pink color indicates nitrites.
Reagents Used
Sulphanilic Acid.—Dissolve 5 gm. in 150 cc. of dilute acetic acid; sp. gr. 1.04.
Naphthylamine Hydrochloride.—Boil 0.1 gm. of solid α-amidonaphthaline (naphthylamine) in 20 cc. of water, filter the solution through a plug of absorbent cotton, and mix the nitrate with 180 cc. of dilute acetic acid. All water used must be free from nitrites, and all vessels must be rinsed out with such water before tests are applied.
1. Would a water showing the presence of nitrites be a safe drinking water? Why? 2. What are nitrites? 3. What does the presence of nitrites indicate? 4. Are small amounts of nitrites, when not associated with bacteria, injurious?