I need input from a good chemist. - dissociation of edetate disodium EDTA (Nov/09/2007 )
C10 H14 N2 O8 Na2 2H2O
Question: When refrigerated a cloudy white precipitate formed in the edta bottle, and when heated to room temperature, this substance almost disappeared. The remaining particles were .25mm in diameter, but after 24 hours, they disappeared to. WHAT WERE THESE REMAINING PARTICLES AND IS THE EDTA ALL RIGHT?
-dave2-
Just adjust the pH to 8.0 with NaOH till it is completely dissolved.
-genehunter-1-
QUOTE (genehunter-1 @ Nov 9 2007, 07:57 AM)
Just adjust the pH to 8.0 with NaOH till it is completely dissolved.
What about heating it to 30C? I can't (don't want to) change the pH. What are the particles?
-dave2-
Internal salt of EDTA with poor solubility.
-genehunter-1-
QUOTE (genehunter-1 @ Nov 9 2007, 10:35 AM)
Internal salt of EDTA with poor solubility.
I thought it was the EDTA. NaOh, water and EDTA is all there is.
-dave2-
EDTA has COOH groups and amino groups which carry opposite charge properties. Internal salt is formed among these functional groups in EDTA at certain pH. The solubility is low, sort of like a protein near its PI. When you titrate the pH to break the interaction, its solubility improves. OK?
-genehunter-1-
QUOTE (genehunter-1 @ Nov 9 2007, 10:48 AM)
EDTA has COOH groups and amino groups which carry opposite charge properties. Internal salt is formed among these functional groups in EDTA at certain pH. The solubility is low, sort of like a protein near its PI. When you titrate the pH to break the interaction, its solubility improves. OK?
Yes I understand this and it makes sense. I increased the temp. to 30C and the salt reattached to these groups. Thank you.
-dave2-