How to Make Ammonium Acetate Solution
Ammonium acetate is a white crystalline salt prepared by mixing ammonia and acetic acid, better known as vinegar. This salt finds use as a buffer chemical for some experiments in biology and chemistry labs. It smells faintly of vinegar and is relatively easy to make; just be sure that the vinegar and ammonia you buy don't contain other chemicals because these could contaminate your end product. Ammonium acetate isn't an especially dangerous chemical, but as with anything else you should make sure you store it out of reach of children.
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Things You'll Need
- Ammonia
- Vinegar
- Beaker (or other glass container)
- Pencil
- Paper
- Calculator
- Goggles
- Graduated cylinder (or other volume-measuring device)
- pH paper
- Stir rod
Instructions
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1
Determine the concentration of the acetic acid in your vinegar and of the ammonia in your ammonia solution. Most store-bought ammonia and vinegar will list concentrations as percent weight per volume, which gives you the number of grams per 100 mL of solution. Vinegar may be in percent by volume, which gives you the number of milliliters of acetic acid per 100 mL of solution.
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If the concentration is percent weight, then replace the percent sign with grams and do the following:
For ammonia: Divide by 17.031 and multiply by 10 to get the number of moles of ammonia per liter of solution.
Example: A 5 percent ammonia solution contains 5 grams of ammonia per 100 mL of product. 5 / 17.031 = 0.294 x 10 = 2.9 moles per liter.
For vinegar: Divide by 60.05 and multiply by 10 to get the number of moles of acetic acid per liter of solution.
Example: A 5 percent by mass vinegar solution contains 5 grams of acetic acid per 100 mL of vinegar. 5 / 60.05 = 0.0833 x 10 = 0.833 moles per liter.
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Ammonia will typically be by percent weight. If the concentration of vinegar is specified in percent by volume, change the percent sign to mL and multiply it by 1.049 grams, then divide by 60.05 and multiply by 10 to get the number of moles per liter.
Example: A 5 percent by volume solution contains 5 mL of acetic acid per 100 mL of vinegar.
5 mL x 1.049 grams per mL = 5.25 grams
5.25 / 60.05 = 0.0873 moles per 100 mL
0.0873 x 10 = 0.873 moles per liter
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4
Divide 0.5 by the number of moles per liter of ammonia. This gives you the number of liters of ammonia solution that will contain 0.5 moles of ammonia. The goal here is to measure out enough of each reactant to make 0.5 moles of product.
Example: 0.5 / 2.9 = 0.172 liters or 172 milliliters of ammonia.
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5
Divide 0.5 by the number of moles per liter of vinegar. This gives you the number of liters of vinegar that will contain 0.5 moles of acetic acid.
Example: 0.5 / 0.833 = 0.60 liters or 600 milliliters.
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6
Put on your goggles. Using a graduated cylinder, measure out the amount of ammonia you calculated into the glass container; in the example, this was 172 mL of ammonia. Make sure you do this in a well-ventilated area.
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7
Measure the amount of vinegar you calculated. In the example it was 600 mL of vinegar. Add the vinegar slowly to the ammonia. Stir the solution gently.
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8
Test the pH of the solution with pH paper. It should be close to pH 7. If the pH is 8 or above, add a little more vinegar and retest pH. If it is 6 or below, add a little more ammonia and re-test pH.
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Tips & Warnings
Ammonia is a weak base while vinegar is a weak acid. When mixed in equal proportions (1 mole to 1 mole), they make a neutral salt. If the proportions are identical, the resulting solution should be neutral in pH; a pH above or below 7 indicates some acid/base remains unneutralized.
Do not attempt to make ammonium acetate this way if the ammonia or vinegar products you are using contain other chemicals. Some window cleaners, for example, contain ammonia but also contain many other chemicals that could participate in other reactions, so you will not get the results you expect.
Always be careful when working with acids and bases; make sure you do not get ammonia or vinegar in your eyes, where they could cause irritation or even serious damage.
Do not attempt to drink or consume the solution of ammonium acetate you have prepared; ammonium acetate prepared in this way is not meant for human consumption.
Do not mix this product with bleach or strong acids.
References
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