[towels]

Hi everyone.

I'm in my first year of chemistry at university and our professor has presented us with an interesting experiment. He's acquired a sample of fermentation waste at a local brewery and wants to know how much ammonia and ammonium is in the sample(mass ammonium+ mass ammonia/ liter sample)

We have to devise the experiment ourselves. Now I've had a few problems and would like to know what you guys think. I'm going to start by filtering the sludge then adding HCl to form the following reaction:

HCl+NH3--> NH4Cl

I was planning on adding NaOH to convert it back to NH3 then doing a distillation(possibly steam assisted?) to evaporate the NH3 but I need some way to stop it evaporating after that.

Then I was planning on doing a titration but I'm not sure what to use as a titrant or an indicator.

Thanks for the help guys.

Towels

[fledarmus]

Wow, that's quite a problem for first-year chemistry!

I'm not sure I follow your experimental plan so far. How do you plan to use either the HCl addition or the NaOH addition/distillation to tell you have much ammonia or ammonium you have in your initial sample?

[towels]

I was thinking that the addition of an acid would cause NH4+ ions to form. so I'd have all my ammonium and ammonia in that form then by adding NaOH the Ph would rise and the NH4+ would become NH3 which I can seperate from the rest of the mixture through destillation( I think) but this leave me with the problem of catching it. I was thinking maybe using an acid to catch it the using a titration with a base to determine how much ammonium/ammonia is in the mixture by using an indicator for when the acid becomes a base ( possibly fonlfetaline). I was wondering if this would work.

[Borek]

I was thinking that the addition of an acid would cause NH4+ ions to form. so I'd have all my ammonium and ammonia in that form then by adding NaOH the Ph would rise and the NH4+ would become NH3

What if you will not add HCl initially? WIll it change anything?

fonlfetaline

You have made my day 

[AWK]

Ammonia in your case can be determined in the following manner.
1.acidification and filtration
2. After addition of an excess  of NaOH - steam distillation of ammonia (and volatile amines).
3. Addition of known amount of HCl to the distillate.
4. Titration of the excess of HCl with NaOH

See:
http://www.titrations.info/back-titration

[jplu]

Trick question concerning last reply:

Does the NaOH react with the NH4Cl in the solution (which is formed by adding HCl to NH3)?

If not, does NH4Cl affect the pH of the solution?

[Borek]

Nothing tricky about your question. NH₄⁺ is an acid.

[jplu]

Correct, but I would like to know if NaOH reacts with the salt NH4Cl rather then exclusively with the excess HCl?

[Borek]

In general strong acids react first.

[Furanone]

Hi everyone.

I'm in my first year of chemistry at university and our professor has presented us with an interesting experiment. He's acquired a sample of fermentation waste at a local brewery and wants to know how much ammonia and ammonium is in the sample(mass ammonium+ mass ammonia/ liter sample)

We have to devise the experiment ourselves. Now I've had a few problems and would like to know what you guys think. I'm going to start by filtering the sludge then adding HCl to form the following reaction:

HCl+NH3--> NH4Cl

I was planning on adding NaOH to convert it back to NH3 then doing a distillation(possibly steam assisted?) to evaporate the NH3 but I need some way to stop it evaporating after that.

Then I was planning on doing a titration but I'm not sure what to use as a titrant or an indicator.

Thanks for the help guys.

Towels

You might want to look into the Kjehldahl method using boric acid as a trap. Kheldahl is typically used for protein determination in foods based on the nitrogen content and a conversion factor. With the proper modifications, I believe it would suit your purposes well for quantifying ammonia (collected before titration with NaOH) and ammonium (separately collected after titration with NaOH ie. newly liberated ammonia).

http://en.wikipedia.org/wiki/Kjeldahl_method