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#Post#: 995--------------------------------------------------
Inorganic qualitative analisys of cations test
DIR By: Chemist@
Date: October 27, 2012, 6:19 am
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Could someone please check if I made this correct (the attached
chart)?
As I am not able to use just any reagent, I made this table from
some of the reagentas that I can use, so for now, I don't want
an answer that there is a better and quicker way to determine a
group. I need to know where did I mistake in this chart (if I
mistaken).
-The thing that troubles me most is e.g: I add H2S and HCl to
check if the unknown cation is from the 2nd group, I get a
precipitate and I write that it is from the 2nd group, but it
was Barium because it makes a precipitate in that conditions,
too (impossible but I just used as an example).
#Post#: 999--------------------------------------------------
Re: Inorganic qualitative analisys of cations test
DIR By: Shiva
Date: October 27, 2012, 8:00 am
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Okay, well, I just simplify the steps for you so you could
detect the cations much easily by using these reagents.
1. Correct.
2. Correct but need not to add hydrochloric acid.
3. Both IIIa & IIIb can be determined by simply adding ammonium
hydroxide. With ammonium hydroxide, Ferric ion precipitates
reddish brown precipitate of Ferric hydroxide, Manganese ion
gives white precipitate of Manganous hydroxide which quickly
turns to brown owing to the formation of Manganic hydroxide. The
remaining two Aluminium & Zinc give white precipitate. In that
case, you can do hydrogen sulfide test. As Aluminium sulfide is
unstable, it will be readily decomposed by water and cannot be
precipitated by passing hydrogen sulfide test but you can do
with Zinc ion. You can also do flame test for confirmation.
4. well, as far as alkaline earth compounds are concerned, you
cannot detect them by passing hydrogen sulfide as most of the
alkaline earth sulfides are unstable and will be decomposed
easily by water. However, you can detect them easily with flame
test. If it is calcium ion, it will impart red brick color to
the flame , apple green for Barium & red for Strontium.
Otherwise, it should be Magnesium ion.
Hope this helps. Please let me know if you have any questions.
Thank you,
Shiva
#Post#: 1004--------------------------------------------------
Re: Inorganic qualitative analisys of cations test
DIR By: Chemist@
Date: October 27, 2012, 10:51 am
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Thanks for the reply.
"4. well, as far as alkaline earth compounds are concerned, you
cannot detect them by passing hydrogen sulfide as most of the
alkaline earth sulfides are unstable and will be decomposed
easily by water. "
I know that, I just wrote an example.
2.HCl is added so I get an acid environment and the III group
cations won't interfere.
Now to the III group.
How do you mean that I can only use NH4OH? I read on few sites
that a buffer has to be made with NH4Cl.
Is there a possibility that Ca2+ precipitates with ammonia
NH4OH?
Should I maybe first test for NH4+ with Nessler and then IV and
V on flame?
#Post#: 1005--------------------------------------------------
Re: Inorganic qualitative analisys of cations test
DIR By: Shiva
Date: October 27, 2012, 1:42 pm
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Of course you can. Soluble calcium salts precipitates Calcium
hydroxide on adding ammonium hydroxide. Yes, you can use
Nessler's reagent for detecting Ammonium ion. But, I do not use
it as it contains extremely toxic mercuric ion and there are
some difficulties in disposing it.
#Post#: 2100--------------------------------------------------
Re: Inorganic qualitative analisys of cations test
DIR By: Chemist@
Date: February 12, 2013, 3:08 pm
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Will SnS precipitate in neutral solutions?
#Post#: 2106--------------------------------------------------
Re: Inorganic qualitative analisys of cations test
DIR By: Michel
Date: February 14, 2013, 12:38 am
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I expect it to precipitate in neutral solution. Sulfides are
generally insoluble and SnS is not an exception
#Post#: 2110--------------------------------------------------
Re: Inorganic qualitative analisys of cations test
DIR By: Chemist@
Date: February 14, 2013, 7:13 am
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The problem is that I found that it is insoluble in weak acidic
solutions, so I wasn't sure about neutral ones.
#Post#: 2111--------------------------------------------------
Re: Inorganic qualitative analisys of cations test
DIR By: Shiva
Date: February 14, 2013, 7:37 am
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In which acid you tried to dissolve?
Shiva
#Post#: 2112--------------------------------------------------
Re: Inorganic qualitative analisys of cations test
DIR By: Chemist@
Date: February 14, 2013, 11:07 am
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Didn't try anything, I saw it in a book.
#Post#: 2113--------------------------------------------------
Re: Inorganic qualitative analisys of cations test
DIR By: Shiva
Date: February 14, 2013, 11:44 am
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oh, well, I have only two tin salts - Stannous chloride &
Stannous sulfate and both are acidic in nature. They are poorly
soluble as well and should be dissolved in corresponding acids
to get a clear solution. So, can't test it with available salts.
As far as I know, it may dissolve in glacial acetic acid as
Stannous acetate is soluble in water but slowly so it appears it
is insoluble in water.
Shiva
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