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Topic: Dissolving BaSO4  (Read 8469 times)

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Offline saN

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Dissolving BaSO4
« on: April 11, 2007, 03:02:05 PM »
I am doing an qualitative analysis of metal cations, and Ba+2 may be present. I know that BaSO4 is insoluble in water, but how would I dissolve this solid and precipitate Ba+2 with something else to confirm that Ba+2 is indeed present? My method to re-precipitate Ba+2 is to add CrO4-2 ions, which will make a yellow precipitate, correct? I just want to find a way to dissolve the BaSO4. Any help will be greatly appreciated!

Offline FeLiXe

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Re: Dissolving BaSO4
« Reply #1 on: April 11, 2007, 05:32:10 PM »
the typical way is cooking it with excess soda. then take the precipitate, dissolve it in HCl and you have soluble BaCl2.

barium chromate will precipitate (even in solution with dilute acetic acid). it doesn't say what color and I don't remember

also look at the flame. if it makes the flame green you can be pretty sure it's barium
Math and alcohol don't mix, so... please, don't drink and derive!

Offline saN

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Re: Dissolving BaSO4
« Reply #2 on: April 11, 2007, 05:35:11 PM »
What do you mean by "cooking" it? Do you mean by putting the solid in any soda and boil it then add K2CrO4?

Offline FeLiXe

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Re: Dissolving BaSO4
« Reply #3 on: April 11, 2007, 05:52:09 PM »
ok "cooking" is the wrong translation for what I wanted to say, it's boiling

take the solid powder, add 3 times as much Na2CO3, add some water, boil it for at least 5 minutes

keep the precipitate and discard the solution. it works best with a centrifuge.

add water to the precipitate then add dropwise acetic acid to dissolve it. you will notice CO2 bubbles.

with chromate the precipitate should form
Math and alcohol don't mix, so... please, don't drink and derive!

Offline AWK

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Re: Dissolving BaSO4
« Reply #4 on: April 12, 2007, 01:59:54 AM »
the typical way is cooking it with excess soda. then take the precipitate, dissolve it in HCl and you have soluble BaCl2.

barium chromate will precipitate (even in solution with dilute acetic acid). it doesn't say what color and I don't remember

also look at the flame. if it makes the flame green you can be pretty sure it's barium
The better way is to use directly an acetic acid for dissolution of barium carbonate.
Moreover, this reaction equilibrates very slowly. 1-15 min of boiling is enough for detection of barium cation
AWK

Offline saN

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Re: Dissolving BaSO4
« Reply #5 on: April 13, 2007, 04:48:35 PM »
I will try the simplest and safest way as to the time constraints.

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