[zarabat]

Hi there,

I want to separate boric acid (B(OH)3) form hydrochloric acid (HCl), all are in liquid medium(H2O). I was thinking to precipitate HCl with AgNO3 then filter it. But as boric acid is also not soluble in water it is not a good idea. Could you please give me some ideas?

Thanks all
 

[Hunter2]

What about destillation. Boric acid is a solid material.

[zarabat]

Thanks hunter for your reply

Yes actually it is very good idea. But i forget to mention that in my solution I also have Mg ions!

Actually my solution is mixture of boric acid, HCl and Mg2+, lets say I distillate it how can I get ride of Mg ion?

thanks for your responds 

[kriggy]

Why do you want to separate those compounds?
I think you could destilate the HCl away and then dissolve it again, use some kind of chelating agent for Mg and then use chromatography to separate it from boric acid.

[Babcock_Hall]

IIRC boric acid derivatives have a strong affinity for vicinal diols.  I seem to recall a paper which used a carbohydrate matrix of some sort to retard or to capture a borate.

[Borek]

IIRC boric acid derivatives have a strong affinity for vicinal diols.  I seem to recall a paper which used a carbohydrate matrix of some sort to retard or to capture a borate.

Titration after addition of mannitol is a well known alkalimetric method of determining boric acid.

[zarabat]

Thanks all ...
My aim is extracting Boric acid from this mixture,

Bobcock could you please write name of that paper? I can either capture Mg by chelating or precipitate boric acid acid by carbohydrate

Borek I read they will form a complex, I wonder how can I get rid of that complex with mannitol?
 

[Borek]

Borek I read they will form a complex, I wonder how can I get rid of that complex with mannitol?

I am not saying it is doable, I was just enforcing what Babcock wrote.

[Hunter2]

@ zarabat: what do you like to do? Do you want to seperate each component ==> I think not possible, to have MgCl₂, H₃BO₃ and HCl seperatet.  Or do you want to do an analysis of your mixture. The methods aready given above.

[Babcock_Hall]

About 18 months ago, there was a similar thread at chemicalforums.  It might be worth searching to find it.

[zarabat]

Thanks all

Hunter: I have mentioned it in my previous post, my aim is extracting boric acid from the mixture of Mg2+(MgCl2) and HCl not analysis the concentration .

Bobcock I have searched before posting, I found just a thread on analyzing boric acid from a solution!

[kriggy]

May I ask why do you want to separate them? If you want to have pure boric acid isnt better idea just to buy it at sigma?

[Babcock_Hall]

Babcock I have searched before posting, I found just a thread on analyzing boric acid from a solution!

Did you find this thread?  This is the one that I remembered:  http://www.chemicalforums.com/index.php?topic=57646.msg207493#msg207493

[zarabat]

Kriggy, actually we bought it from sigma but by mistake it contaminated with Mg! as it was Boric acid with boron 10 price is high!

Thanks Bobcock, I have seen this before

[Dan]

A strongly acidic ion exchange column will remove Mg²⁺, replacing it with 2H⁺. This then leaves you with HCl and boric acid in water (assuming the counterion to Mg is Cl) - evaporation should leave boric acid.

However, it would be more economical to buy more boric acid - its only £30-£40 for 1 kg from Sigma.