[Anaya]

Hey, I'm new to this board. Name's Ana. 

Um, I have a question for a lab report in my Quantitative Analysis class that tells me to look in a textbook to find methods of volumetrically determining chloride concentrations other than Fajans', only the textbook we're using doesn't really say anything. I'm looking online, but there's a lot of incomprehensible gobbledygook to sift through. I was hoping maybe someone here had an idea?

[Arkcon]

OK.  You want to determine chloride concentration.  You have to do it volumetrically.  Hmmm.  A bit tricky.  You are not allowed to use Fajan's method.  I'm not familiar with that one by name -- what is it's method?

Your Google searches are confusing gobbledygook, OK, what sort of topics are they mentioning -- are you getting bogged down in ion selective electrodes and ion chromatography methods?  Or gravimetric methods?  Is that the problem?

[Anaya]

Fajans' method is based on the use of an adsorption indicator, where the endpoint happens on the precipitate surface (I'm pretty sure the only way to volumetrically determine Cl is precipitation titration). If it helps, I'm using DCFS as the indicator (dichlorofluoroscein).

And the stuff I'm getting on google is basically a bunch of formal lab reports that I can only see the abstract of anyway, so they're useless.

[ARGOS++]

Dear Anaya;

Do you know as an alternative Detection/Indicator: “Kohlraush’s Law”?

You may read on:  "Kohlrausch’s Law”

I hope to have been of some help to you.
Good Luck!
                    ARGOS⁺⁺

[Anaya]

I don't understand how that applies to my question.  Unless the law suggests some type of assay...?

[Arkcon]

I'm still trying to wrap my mind around your assignment ... search your textbook, for a chloride determination method, not Fajans' ... so, go and do that. 

OK.  A quick Google leads me to a bunch of methods.  Makes sense, this is kinda important, so it's logical a bunch of methods exist.  How do these work for you?

http://64.233.169.132/search?q=cache:NQ7EViQGItsJ:itc.gsw.edu/faculty/tiordano/PDF/Quant/Lab%25205%2520volumetric%2520chloride.pdf+volumetric+chloride+determination&hl=en&ct=clnk&cd=1&gl=us&client=firefox-a

http://64.233.169.132/search?q=cache:MAUwIV1HhVcJ:www.towson.edu/~topping/Experiment3Chem210.doc+volumetric+chloride+determination&hl=en&ct=clnk&cd=2&gl=us&client=firefox-a

http://www3.interscience.wiley.com/journal/113322946/abstract

[ARGOS++]

Dear Anaya;

Maybe you know it better under: “Conductivity Titration”.
The last picture/right side corresponds to your situation of precipitation.

I hope this is giving you at least an idea.

Good Luck!
                    ARGOS⁺⁺

[Anaya]

But do conductimetric and spectophotometric assays count as volumetric? I'm not sure I really understand the mechanisms...

[ARGOS++]

Dear Anaya;

Of course that “Conductivity Titration” is a “normal” volumetric Method, only the Indicator has changed.
For spectroscopy it depends on how you the method design.

Good Luck!
                    ARGOS⁺⁺

[Anaya]

Okay, correct me if I'm wrong... The mechanism of the conductimetric titration in my case would have the AgCl and HCl being titrated with some hydroxide base (probably NaOH?) to form AgCl, NaCl, and H2O, with phenolphthalein as the indicator. The reaction at the conductivity meter is between NaOH and HCl, and the endpoint is when the meter is at the lowest point and the phenolphthalein goes from pink to colorless? I've never done this type of titration before, so I'm not sure...

[ARGOS++]

Dear Anaya;

Your “Picture” os not very correct for the situation.

Let’s do it with the last picture of the Link I presented, because it’s very simple:

You use still AgNO3 as the Titrant, and only your acidic sample, as exactly in the picture.
At the start you measure a certain “Kappa” (Conductivity), and that will be kept nearly constant, as long as
Precipitation occurs, because the total number of ions is still constant. At the Endpoint you start to add by your Titrant additional Ions, because precipitation is finished, and so the Kappa starts to rise linear as in the picture. At the Intersection of both “legs” you can read the required amount of the Titrant for equivalence.

You can see: it’s at least as simple as a normal Titration.

I hope to have been of help to you.
Good Luck!
                    ARGOS⁺⁺

[Anaya]

I'm sorry, I'm still not 100% on this. Does that mean that the chloride sample first has to be protonated, to make it acidic?

[ARGOS++]

Dear Anaya;

No, HCl is already a strong Acid by itself; but it works also for NaCl and all soluble Chlorid-salts or Bromid-Salts.

Good Luck!
                    ARGOS⁺⁺

[Anaya]

Oh, okay! And obviously, if I have a liquid sample of chloride + whatever, the chloride is in soluble salt form, and is therefore working as an acid. For some reason, I had it confused with gravimetric determination where it was precipitated into AgCl, but that's what the titration is doing... Okay, I get it now! Thanks!

[ARGOS++]

Dear Anaya;

You’re welcome!   ─   Soon again.

Good Luck!
                    ARGOS⁺⁺

P.S.:  For once you may also raed on ‘Wiki’: “Titration”, too.
.