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#Post#: 2278--------------------------------------------------
Re: Inorganic qualitative analisys of cations test
DIR By: Chemist@
Date: March 9, 2013, 9:42 am
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Great reaction. I couldn't find a very specific reaction for
aluminium, but this one changed things.
Now to distinguish between the sulfides. Is the specific
reaction for Sn2+ the one with HgCl2? No other cation will react
similar?
#Post#: 2280--------------------------------------------------
Re: Inorganic qualitative analisys of cations test
DIR By: Shiva
Date: March 9, 2013, 12:05 pm
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Yes, as I said, Stannous ion will reduce Mercuric chloride to
metallic Mercury. Unless, it is not a reducing agent, yes.
#Post#: 2281--------------------------------------------------
Re: Inorganic qualitative analisys of cations test
DIR By: Chemist@
Date: March 9, 2013, 12:24 pm
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Mn2+ is a reducing agent, too. Should I expect that it reacts
with HgCl2 similar as Sn2+?
#Post#: 2284--------------------------------------------------
Re: Inorganic qualitative analisys of cations test
DIR By: Shiva
Date: March 9, 2013, 1:39 pm
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Yeah, but, Mn2+ ions are generally not included in the list of
reducing agents because they are extremely weak as reducing
agents. I do not think they will reduce Mercuric chloride to
metallic mercury like some Stannous salts do. As Mercury
compounds can be easily reduced, may be it will be reduced to
Mercurous chloride.
Shiva
#Post#: 2285--------------------------------------------------
Re: Inorganic qualitative analisys of cations test
DIR By: Chemist@
Date: March 10, 2013, 4:37 am
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Shiva, I really don't know how to express my thankfulness to
you. I wouldn't bother you, but I don't have where to try these
tests, so I had to ask so many questions here. I almost reached
the end, but three critical points still remained:
1. Tin & Manganese both produce a brown precipitate with
sulfides and both reduce HgCl2. I need some test to be 100% sure
which ion I have. What should I do? I found the Mn2+ test with
PbO2 and HNO3 to produce purple MnO4-, but I don't know if I can
do it properly. I found out that their hydroxides have different
colors (tin is white and manganese is yellow). Is this true?
2. Distinguishing between Ca and Mg without the flame test (I
never did it previously so it has to be my last resort). If I
add a hydroxyde, magnesium will precipitate immediately, if I
add oxalate, now calcium will. Is this good?
3. Both acetates and chlorides produce fumes upon adititon of
sulfuric acid. Is there another way to distinguish between these
two other that the odor of the acetates? I relied on the odor
last year and failed :(.
#Post#: 2286--------------------------------------------------
Re: Inorganic qualitative analisys of cations test
DIR By: Shiva
Date: March 10, 2013, 5:04 am
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No worries buddy :) Questions are always welcome. I love to talk
about chemistry :)
1. On adding Sodium hydroxide solution, Tin salts will give
white precipitate whereas Manganese ions will give brown
precipitate (Distinct from tin)
2. On adding dilute sulfuric acid, Calcium ions will give white
precipitate of Calcium sulfate whereas Magnesium compounds do
not
3. Chlorides give white precipitate with Lead nitrate solution
whereas acetates do not give any precipitate as Lead acetate is
soluble in water.
#Post#: 2287--------------------------------------------------
Re: Inorganic qualitative analisys of cations test
DIR By: Chemist@
Date: March 10, 2013, 5:12 am
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--- Quote from: Shiva link ---
>
> 3. Chlorides give white precipitate with Lead nitrate solution
whereas acetates do not give any precipitate as Lead acetate is
soluble in water.
>
--- End Quote ---
I thought the same, but lead nitrate isn't on the list of the
reagents available for use :(.
#Post#: 2288--------------------------------------------------
Re: Inorganic qualitative analisys of cations test
DIR By: Shiva
Date: March 10, 2013, 5:27 am
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Oh sorry! Unfortunately, Ferric chloride solution is not among
the list either. I'm thinking if there is a way to detect
acetates quite easily without these reagents. I will come up
with an answer as quickly as possible :)
Shiva
#Post#: 2289--------------------------------------------------
Re: Inorganic qualitative analisys of cations test
DIR By: Chemist@
Date: March 10, 2013, 11:46 am
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I got an idea. Silver chloride is soluble in ammonia, while I
didn't read the same for silver acetate. Maybe this method could
help me separate chloride from acetate.
#Post#: 2290--------------------------------------------------
Re: Inorganic qualitative analisys of cations test
DIR By: Shiva
Date: March 11, 2013, 5:35 am
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No, silver acetate is soluble in Ammonium hydroxide too. I know
a way but it is a bit dangerous. I've noticed Lead peroxide is
among your reagents list. Lead dioxide can be converted to Lead
nitrate by warming it up with dilute nitric acid. But. be
careful. Lead peroxide is extremely toxic and carcinogenic and
it should be handled with utmost care. Once all Lead peroxide is
dissolved in nitric acid, allow the solution to cool. Then, if
the provided sample is chloride, it will give white precipitate
and none with acetates. Please let me know if you have any
questions.
Shiva
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