ehsan - 16-11-2014 at 19:36
how can lead and antimony be seperated from a Pb-Sb alloy using nitric acid?
if i use HNO3 for the alloy opening, then physically what type of reaction it would be? plz help 
Etaoin Shrdlu - 16-11-2014 at 20:16
Good question. You may want to consider:
How does lead react with nitric acid? Are any special conditions required? What are the characteristics of the product?
How does antimony react with nitric acid? Are any special conditions required? What are the characteristics of the product?
HgDinis25 - 17-11-2014 at 12:53
This should be in Beginnings.
If you had an alloy of Lead and Antimony to Nitric Acid, then you'll have a reaction between Nitric Acid and Lead and a reaction between Nitric Acid
and Antimony.
Lead reacts with concentrated Nitric Acid as follows:
Pb(s) + 4HNO3(aq) --> Pb(NO3)2(aq) + 2H2O(l) + 2NO2(g)
However, if diluted Nitric Acid is used, the following reaction is favoured:
3Pb(s) + 8HNO3(aq) --> 3Pb(NO3)2(aq) + 2NO(g) + 4H2O(l)
Although Lead(II) Nitrate is soluble in water, if you add more concentrated Nitric Acid it will precipitate.
The reaction between Antimony and Nitric Acid is a little bit more tricky. It can oxidize Antimony either to Sb(III) Oxide or Sb(V) Oxide. However the
reaction is very slow at room temperature. It usually forms Sb2O3 if Nitric Acid isn't in excess, though. Both are insoluble in water.
Another way to seperate Antimony from Lead is by using Sulfuric Acid. Add your alloy to concentrated sulfuric acid and heat it (50ºC should be enough
to make a fast steady rate of reaction). Antimony will react to form Antimony(III) Sulfate as follows:
2Sb(s) + 6H2SO4(aq) → Sb2(SO4)3(aq) + 3SO2(g) + 6H2O(l)
Lead may also slowly react with Sulfuric Acid in the conditions described to form Lead(II) Sulfate. This is insoluble in water and won't be a problem.
As soon as the reaction is done, dilute it with an equal volume of water. This is ti ensure any leftover Sulfuric Acid is diluted enough to allow for
all the Antimony(III) Sulfate to go into solution. Filter the solution to remove any leftover alloy or Lead(II) Sulfate. Boil it to produce a
concentrated soulution (boiling should be made in a middly acidic solution to avoid any possible hydrolysis).
Anyway, it would help if we knew your end game. Do you want to recover Antimony metal or do you need the Nitrate specifically?
diddi - 17-11-2014 at 15:28
that's a lot of acid to use up if you have a big lump. why not try using Pb/Sb as sacrificial electrode.