Talk:Fehling's solution

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General clarification

I attempted to name the complex Wikipedia gives as the oxidising agent, but overall I think it would be useful if someone could clarify the reaction mechanism and exactly what happens. The equations on the page were also conflicting so I removed one of them (the one which suggested the copper-tartrate complex was cationic - I hope I picked the right one!) This webpage suggests that a green suspension is formed along with a red ppt as a positive result, and I do remember this happening from doing the test myself. Also it gives a different structure for the copper-tartrate complex. If someone could clarify the correct complex structure and possibly add an example arrow-pushing mechanism, that would be great. Zynwyx (talk) 20:35, 23 January 2011 (UTC)[reply]

Is the reaction correct ?

When I started to check if the reaction was correct I found out that it might be false (please answer what you think of it)

First of all, why is there 2Cu2+ in the begininng ? since the bistartratocuprate(II) has only one ? And isn't there missing 2H20 in the end ?

To conclude, this is what I think the reaction should be (we can remove the elements which aren't reacting):

2Na+ + 2(C4H4O6)2- + 2K+ + Cu2+ + 2OH- -------> [Cu(C4H3O6)2]4- + 2Na+ + 2K+ + 2H2O

There might be an other possibility where one of the O- of each Potassium sodium tartrate reacts with the Cu2+ instead of one of the OH - which would mean the drawing is false -(causing the loss of an H, as seen just before, which is caught by an OH- to form H2O), so the reaction becomes :

2Na+ + 2(C4H4O6)2- + 2K+ + Cu2+ + 2OH- -------> [Cu(C4H4O6)2]2- + 2Na+ + 2K+ + 2OH-

Again please tell me what you think and to understand what i meant, try drawing the molecules

P.S : I'm goint to start my second year of my technical degree in chemistry — Preceding unsigned comment added by Celte2 (talk • contribs) 17:27, 18 August 2012 (UTC)[reply]

You are correct, the first reaction is the correct one.JSR (talk) 17:36, 18 August 2012 (UTC)[reply]

Ok thank you so I'm going to edit the picture and try to upload the correct version. It might take some time since I've never done that — Preceding unsigned comment added by Celte2 (talk • contribs) 18:19, 18 August 2012 (UTC) May I use this opportunity to ask you a few questions ? Do you know the ph of the fehling's solution ? And if it reacts, for example, with glucose only when its in an alkaline environment ? — Preceding unsigned comment added by Celte2 (talk • contribs) 21:46, 18 August 2012 (UTC)[reply]

You should sign your posts. The use 4 ~'S at the end of the post will automatically sign your post. The pH would be basic, but I have not seen what the pH would be. It would be reacted with sugars at the pH level found under the conditions of the test. It's been years since I've looked at the procedure.JSR (talk) 23:10, 18 August 2012 (UTC)[reply]

It seems I've made an error also, its [Cu(C4H3O6)2]4-. So if the glucose solution is pH=1, the reduction of glucose will still happen ?Celte2 (talk) 13:45, 20 August 2012 (UTC)[reply]

Had not noticed that. The pH of the test solution is a part of the test. I do not remember how the test is conducted, but the test method utilized will be standardized. To be useful, if glucose is present, it give a positive test.JSR (talk) 13:51, 20 August 2012 (UTC)[reply]