Micro-chemical test for ammonia: Difference between revisions
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== Principle == | == Principle == | ||
When dissolving a salt containing ammonium in an alkaline 2M NaOH solution, gaseous ammonia (NH<sub>3</sub>) is liberated which has a typical | When dissolving a salt containing ammonium in an alkaline 2M NaOH solution, gaseous ammonia (NH<sub>3</sub>) is liberated which has a typical smell and will change the color of a previously wetted yellow pH indicator paper to green or blue. | ||
== Procedure == | == Procedure == | ||
Add a drop of 2M sodium hydroxide, i.e., | Add a drop of 2M sodium hydroxide, i.e., caustic soda, to a drop of the sample solution and immediately hold a wetted pH indicator paper directly above it into the released vapors. | ||
or | or | ||
put drop of sodium hydroxide solution (2M )on | put drop of sodium hydroxide solution (NaOH 2M ) on a microscope slide and then put one grain of the salt into it. Hold a wetted pH indicator paper directly above the preparation into the liberated vapors, while the salt is still dissolving. | ||
'''Indications from the pH-value of the salt solution''' | '''Indications from the pH-value of the salt solution''' | ||
The pH value of an aqueous solution of nitrammite [NH<sub>4</sub>,K (NO<sub>3</sub>)], (also known as gwihabaite) is slightly acidic (circa pH 5). If the sample solution is acidic this is no proof for the presence of ammonium nitrate but it is a first indication | The pH value of an aqueous solution of nitrammite [NH<sub>4</sub>,K (NO<sub>3</sub>)], (also known as gwihabaite) is slightly acidic (circa pH 5). If the sample solution is acidic this is no proof for the presence of ammonium nitrate but it is a first indication. | ||
== Literature == | == Literature == | ||
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<biblist/> | <biblist/> | ||
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[[category:Bläuer,Christine]][[category: | [[category:Bläuer,Christine]][[category:approved]][[category: microchemistry]] | ||
Latest revision as of 20:21, 24 November 2017
Author: Christine Bläuer
back to Micro-chemical testing
For more information on the required equipment and materials see the Micro-chemistry article.
Principle
When dissolving a salt containing ammonium in an alkaline 2M NaOH solution, gaseous ammonia (NH3) is liberated which has a typical smell and will change the color of a previously wetted yellow pH indicator paper to green or blue.
Procedure
Add a drop of 2M sodium hydroxide, i.e., caustic soda, to a drop of the sample solution and immediately hold a wetted pH indicator paper directly above it into the released vapors.
or
put drop of sodium hydroxide solution (NaOH 2M ) on a microscope slide and then put one grain of the salt into it. Hold a wetted pH indicator paper directly above the preparation into the liberated vapors, while the salt is still dissolving.
Indications from the pH-value of the salt solution The pH value of an aqueous solution of nitrammite [NH4,K (NO3)], (also known as gwihabaite) is slightly acidic (circa pH 5). If the sample solution is acidic this is no proof for the presence of ammonium nitrate but it is a first indication.