[Abilio]

Hi,

I need to prepare a Bi (III) solution and I have BiONO3.H2O in my lab...  I tried to dissolve this salt in water + HNO3 and this is not working. What can I do?

[Alberto_Kravina]

Try to dissolve it in hot conc. sulfuric acid (CAREFULLY!!), afterwards diluite the solution.
I remember that I analyzed a mineral containing Bismuth(III) oxide a while ago. The Oxide was completely dissolved after boiling it with conc. sulfuric acid.

[Abilio]

Thanks,

It works with HNO3 + H2SO4...

But, another question:  What I have in solution? Bi3+ or BiO+???

[Alberto_Kravina]

I think that it is Bi³⁺. Since strong acids are involved the H⁺ ion protonates the BiO⁺, I think.
By the way, were the acids (both nitric and sulfuric) concentrated or diluite?

[Abilio]

Diluite but the pH is < 1

I need a pH = 3 solution... Do you think that if i increas the pH the BiO⁺ will precipitate again???

[Alberto_Kravina]

I need a pH = 3 solution... Do you think that if i increas the pH the BiO+ will precipitate again???

Nah, in my opinion the only reaction that could (partially) interfear is the hydrolisis of Bi³⁺ to Bi(OH)₃

[AWK]

I need to prepare a Bi (III) solution and I have BiONO3.H2O in my lab...  I tried to dissolve this salt in water + HNO3 and this is not working. What can I do?

Add some excess of HNO3 and warm. BiONO3 will dissolve forming Bi 3+  on the condition that the final pH will be lower than about 2-3

[Abilio]

Add some excess of HNO3 and warm. BiONO3 will dissolve forming Bi 3+  on the condition that the final pH will be lower than about 2-3

I really tried this option but doesn't dissolve, then i've added sulfuric acid and it was dissolved... Now, when the solution get ambient temperature it was cristalized, i think this is Bi(OH)₃ like Alberto said.

Any suggestion?

[Alberto_Kravina]

I really tried this option but doesn't dissolve, then i've added sulfuric acid and it was dissolved... Now, when the solution get ambient temperature it was cristalized, i think this is Bi(OH)₃ like Alberto said.

Centrifugate the precipitate, remove the fluid and try to dissolve the solid ppt. in mineral acid (HCl).
If the ppt. is Bismuth(III) hydroxide it shoud dissolve in HCl as BiCl₃

[Abilio]

 

My situation:

I have dissolved the BiONO₃ in nitric acid + sulfuric acid (no heating)... Minutes later something was cristalized, it seems like the solution was reacting wth something in the air (the pH < 1, so it  can't be Bi(OH)₃ and the color is not the color of Bi₂O₃...

What's the problem???

[woelen]

Bi(3+) ions are VERY prone to hydrolysis. Even at a pH equal to 0 they cannot exist, and basic salts are precipitated. In very concentrated acids, you can have clear solutions of Bi(3+), but only at low to medium concentration.

When hydrochloric acid is used, the situation is somewhat better. A complex is formed, BiCl4(-), which is somewhat less prone to hydrolysis, but also with this, a pH of 2...3 will not be feasible. You need a complexing agent in order to keep the Bi in solution at such "high" pH.

The crystals you had could be Bi2(SO4)3. At the high concentrations of acid, the sulfate may crystallize from the solution. I do not think it reacted with something in the air. It is just crystallization of a concentrated solution.