Micro-chemical test for ammonia

Author: Christine Bläuer

back to Micro-chemical testing

More information about the necessary equipment and materials see Article Micro-chemistry.

Principle

When dissolving a salt containing Ammonia in NaOH alkaline vapors extrivate having a typical odor and which will change the color of a previously wetted yellow pH indicator paper to green or blue.

Procedure

Add a drop of caustic soda solution to a drop of the sample solution and immediately hold a wetted pH indicator paper directly above it into the extrivating vapors.

or

put drop of caustic soda solution on an object slide and then put one grain of the salt into it. Hold a wetted pH indicator paper directly above the preparation into the extrivating vapors, while the salt is still dissolving. Indications from the pH-value of the salt solution.

The pH value of an aqueous Nitrammite solution is slightly acidic (circa pH 5). If the sample solution is acidic this is no proof of Ammonium nitrate but it can be a first indication.

Literature

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