[Rutherford]

Is someone willing to check the way how I planned my qualitative analisys of cations,is it correct or I missed something? It is very important to me. If not, I will understand.

[kevinkevin]

  Could I give it a look?  I would like to see if I can help, I believe I can.   

[Rutherford]

I will send you.
How to prove what cations and anions make a salt if that salt is insoluble in water?

[Borek]

You either use some spectroscopic method, or find a way of dissolving the salt.

[Rutherford]

What way to dissolve it?

[Borek]

Hot strong acid, fusion with sodium carbonate or something like that.

Go to the library and browse any serious book on the classical analytical chemistry, such methods will be described there.

[Rutherford]

You mean, I dissolve it in HNO₃, HCl, H₂SO₄ or similar and then do the analisys as in water?

[Arkcon]

Why not try, as best you can, to post your proposed method for everyone to see so we can all help.

[Rutherford]

I need to modify it. Didn't think that I can get a salt insoluble in water. Now I am freaked out  .

[kevinkevin]

  If you can't buy an insoluble salt you can make one, its very easy. 

[Borek]

  If you can't buy an insoluble salt you can make one, its very easy. 

His problem is not with finding an insoluble salt, but with analyzing it.

[Rutherford]

Yes, I need the quickest and easiest way.

[Rutherford]

Ok, this is mine final version, so if you find a mistake please alert me!
The cations are Ag⁺, Pb²⁺, Hg²⁺, Cu²⁺, Fe³⁺, Al³⁺, Ba²⁺, Mg²⁺, Ca²⁺, NH₄⁺.
1. I add K₂CrO₄ (after the ion I will write the colour of the precipitate):
Ag⁺ red
Pb²⁺ dark yellow
Hg²⁺ orange
Cu²⁺ dark brown
Ba²⁺ light yellow
Others don't make a precipitate.
2. If I don't see anything of this I add then NH₄OH:
Fe³⁺ dark orange
Al³⁺ white
Mg²⁺ white ( I add some HPO4- ions and a brown precipitate will be made so I can differentiate from Al³⁺)
3. I add K₂C₂O₄ and if a white precipitate is made it is Ca²⁺.
4. At the end I add Nessler's reagent and a brown precipitate should be made for NH₄⁺.

[Arkcon]

That's not a bad method.  Question:  is the solution just one cation, or is it a mixture of a few of those listed?  Or will you eventually have to do a qualitative analysis of a complex mixture?  In that case, maybe you want to work on a tree-type procedure.

Also, look at what you've said you'll do in step 4, and then look at step 2.  See a problem?  You may have to specify a different way of handling the sample.

[Rutherford]

I will be given a salt made from 1 cation that I listed and 1 anion (no complex mixture). The anions are NO₃^-, CO₃^2-, Cl^-, SO₄^2- and CH₃COO^-.
Maybe I should switch step 4 and step 2 (because of NH₄⁺)?