Ammonia nitrogen from distillation and acid titration.
Ammoniacal Nitrogen Calculator: Free Online Tool
Ammoniacal nitrogen is the nitrogen present as ammonia and ammonium in water or wastewater. It matters because ammonia is toxic to fish, uses up oxygen as it oxidises and is a regular parameter in drinking water, effluent and river water monitoring.
This calculator converts the results of a distillation and acid titration into NH3-N in mg/L. In this method the ammonia is distilled into boric acid and then titrated with standard sulphuric acid. You enter the acid normality, sample volume, sample and blank titres and any dilution factor. The result is also shown as ammonia (NH3) and ammonium (NH4+), which helps when a report asks for a specific form. The tool works in feet and inches or in metres and millimetres, so it suits both older site practice and metric drawings, and every result can be rechecked by hand.
When to use this calculator
Use it after you have distilled a sample into boric acid and titrated the distillate with sulphuric acid. It suits water quality laboratories, wastewater treatment plant testing, environmental consultants and students doing a lab report. It is also useful when you have diluted a high-strength sample, since the dilution factor is built in. Use the titre of the distillate collected in boric acid, and run a blank with the same procedure so that reagent effects are subtracted. It also gives a quick check on quotations and site requests before work starts.
How to use the Ammoniacal Nitrogen Calculator
- Open the calculator above on your phone, tablet or computer. Nothing needs to be installed and no sign-up is required.
- Enter your values in the input boxes: Normality of H₂SO₄ titrant (N), Sample volume (ml), Sample titre A (ml), Blank titre B (ml), Dilution factor (1 if undiluted). The boxes already hold sample values, so overwrite them with your own.
- Press Calculate. The result appears straight away under the button.
- Change any value and press Calculate again to compare options. Press Reset to go back to the sample values.
- Check the result against your drawings, project specification and local code before you order material or approve work.
How the calculation works
The calculator uses NH3-N (mg/L) = (A - B) x N x 14000 / sample volume x dilution factor. A is the acid used for the sample and B the acid used for the blank, both in ml, N is the normality of the sulphuric acid, and the sample volume is in ml. With 0.02 N acid this becomes (A - B) x 280 / sample volume, because 1 ml of 0.02 N acid equals 280 micrograms of nitrogen. With the defaults (0.02 N, 100 ml, A = 6.4 ml, B = 0.4 ml) the result is 16.80 mg/L as N, 20.43 mg/L as NH3 and 21.63 mg/L as NH4+.
Worked example
When you open the page the calculator is filled with sample values. Pressing Calculate with those values gives the result below, which you can use to check that you are reading the output correctly.
| Result | |
|---|---|
| Ammoniacal nitrogen, NH₃-N (mg/L) | 16.80 |
| As ammonia, NH₃ (mg/L) | 20.43 |
| As ammonium, NH₄⁺ (mg/L) | 21.63 |
Tips and common mistakes
- Enter the real normality of your sulphuric acid after standardisation. Using 0.02 N when the acid is slightly different gives a proportional error in the result.
- Always run a blank and enter its titre in B. The sample titre A must be larger than the blank titre.
- Use the volume of the original sample taken for distillation, in ml, not the volume of the distillate or the receiving boric acid.
- If you diluted the sample before distillation, enter the dilution factor. If you did not, leave it as 1.
- Check which form your report needs. NH3-N, NH3 and NH4+ are different numbers for the same sample, so label the units clearly.
Frequently asked questions
What is the difference between NH3-N and NH3?
NH3-N expresses only the mass of nitrogen in the ammonia, while NH3 expresses the whole molecule. The calculator shows both, so with the default data 16.80 mg/L as N equals 20.43 mg/L as NH3.
Where does the 280 factor come from?
With 0.02 N sulphuric acid, 1 ml of the acid equals 280 micrograms of nitrogen. So the general formula with 14000 simplifies to (A - B) x 280 / sample volume when the acid is 0.02 N.
Which titre goes in A and which in B?
A is the acid used for the sample distillate and B is the acid used for the blank. Both come from titrating the boric acid receiving solution. The sample titre should be higher than the blank.
Do I need to enter a dilution factor?
Only if you diluted the sample before the test. Enter the factor, for example 10 for a 1 to 10 dilution, and the calculator multiplies the result by it. Otherwise leave it at 1.
Does this calculator include distillation efficiency?
No. It only does the titration arithmetic from your readings. It does not correct for distillation losses, so follow your standard procedure to ensure complete ammonia recovery.
Important note
This tool gives estimates for planning, study and quick checks. It does not replace design by a qualified engineer, site-specific testing, or the requirements of your project specification and local building code. Always confirm final quantities, test results and acceptance limits with the responsible engineer before using them for construction or payment.
