Brine Electrolysis: Why Is the Solution Turning Yellowish?

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Discussion Overview

The discussion revolves around the phenomenon of a yellowish coloration observed during the electrolysis of brine using carbon electrodes. Participants explore potential causes for this color change, including electrode degradation, chemical reactions, and impurities in the materials used.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant notes the yellowish color may be due to electrode decomposition, suggesting fine carbon particles could be present.
  • Another participant questions the current being used and the condition of the electrodes, indicating that graphite particles could be flaking off and affecting the solution's color.
  • A participant asserts that the yellow color is due to chlorine gas dissolving in the alkaline solution, while another counters that dissolved chlorine is colorless at low concentrations.
  • Concerns are raised about the potential corrosion of connecting wires, particularly if they contain iron, which could contribute to a reddish or yellowish hue.
  • Some participants mention the possibility of potassium iodide in iodized salt affecting the solution's color, while others argue that such a small amount would not have a significant impact.
  • One participant describes observing a precipitate after disconnecting the battery, questioning the presence of sodium hydroxide in the solution.
  • Suggestions are made to conduct experiments on the precipitate to determine its composition and behavior when treated with acids.
  • Questions arise regarding the source of the carbon electrodes and potential contamination from scavenged materials.

Areas of Agreement / Disagreement

Participants express multiple competing views regarding the cause of the yellow coloration, and the discussion remains unresolved with no consensus reached on the primary reason for the observed phenomenon.

Contextual Notes

There are limitations regarding the assumptions made about the materials used, the specific conditions of the electrolysis setup, and the potential interactions between the components involved.

asamaid1
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Hi,
i have been trying to electrolyze brine having carbon as anode and cathode as well;; but i don't understand why the solution is turning yellowish. Can anyone explain it ? thanks.
 
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My bet is that what you see is just effect of electrode decomposition, either very fine carbon particles or just the binding.
 
You say that you are using carbon [graphite] electrodes for both the anode (+) and cathode (-) of you cell. What current are you passing through the cell? How are the electrodes holding up? Is the anode disintegrating at all? Fine graphite particles should be flaking off the anode and making the solution turn gray (or black after a long time).

How are you making your electrical connection to the graphite electrodes from your power supply? Are these wires completely isolated from your electrolyte solution? Do the wires show any signs of corrosion? The graphite electrodes can be porous and a small amount of electrolyte can be absorbed up into the electrode and migrate up toward you wire leads.
 
Hi,

i used carbon rod as electrode, and a 9 volt battery was used, and connecting wire does not touch the solution,,,,,,,,,, so why the solution s turning reddish yellow. thanks.
 
hi
here the correct reason:
the product of the reaction is chlorine at anode and hydrogen gas at cathode and sodium hydroxide solution .the yellowish color produced because some of yellowish chlorine dissolved in the alkali solution .
forgive me all...
 
wazani said:
the product of the reaction is chlorine at anode and hydrogen gas at cathode and sodium hydroxide solution .the yellowish color produced because some of yellowish chlorine dissolved in the alkali solution .

No. Dissolved chlorine is colorless, especially at low concentrations. You will not get high concentrations of chlorine using simple setup like the one described by the OP.
 
possible either Cl2 produced or presence of NaOH to cause corrosion on the conducting wire esp it contains Fe and iron(III) compound is reddish/brown/yellow ? Can carry out simple analytical test on iron(III) ion ? hopefully this will help
 
asamaid1 said:
Hi,

see this you tube link

http://www.youtube.com/watch?v=OoIuDPI5GQs&feature=related


the same thing happens when i do this, but i used carbon for electrodes, and conecting wires do not touch the solution. thaks
The cause of the color change observed in the video is very different from the situation you are describing. In the case of the video, the color change is easily explained by the oxidation of the iron (stainless steel spoons) into Fe+2 (aq) ions in solution. But you claim that you are not using iron, you only use copper and carbon, and the copper is not even touching the solution (If the copper was being oxidized to Cu+2 and put into solution, it would turn blue by the way).

As Borek said, with only a 9 volt battery as your power supply, it is unlikely that you were generating significant quantities of chlorine. Otherwise, that would have been my next guess...that you are generating chlorine that then dissolves in the water, changing its color to a pale yellow (like clorox bleach). But with the setup you describe, I do not think that is happening.
 
  • #10
Hi,

if i disconnect the battery, and leave the solution still , the yellow stuff precipitates at the bottom, and i don't see any sodium hydro oxide, souldnt there be some white sodium hydrooxide at the bottom?thnks.
 
  • #11
Sodium hydroxide is highly soluble in water; it will all remain in solution (and also react with the Cl2 that you are producing, none will precipitate out.

How much of that powder do you get? Enough to do a couple of experiments on it? You could try filtering it out and drying it. Then see what acids will dissolve it, and / or what happens when you heat it up to a high temperature in air.
 
  • #12
Hmmm... You're producing some caustic soda in solution, but not a lot of chlorine...

... What's the material you're using as a container for your electrolyte, and what kind of sealant did you use? Do you have direct means of agitation, or indirect?
 
  • #13
mrjeffy321 said:
How much of that powder do you get? Enough to do a couple of experiments on it? You could try filtering it out and drying it. Then see what acids will dissolve it, and / or what happens when you heat it up to a high temperature in air.
Hi,

thnks for the reply, I did filter it, and tried to dissolve the powder in accetic acid, it does not dissolve. any other ideas? thanks.
 
  • #14
Hello everyone,

you same thing happened to me too, i used a becker for the container, carbon as electrodes, a 9 volt battery, and table salt. Then i saw the solution becoming yellow. Is it something with the salt? because i used table salt, which is iodised. the salt packing says 40 ppm of potassium iodide is mixed with the salt. can anyone shed some light on it? thanks.
 
  • #15
As it was already said - most likely what you see is some junk from the graphite electrode.
 
  • #16
sohel2012 said:
Hello everyone,

you same thing happened to me too, i used a becker for the container, carbon as electrodes, a 9 volt battery, and table salt. Then i saw the solution becoming yellow. Is it something with the salt? because i used table salt, which is iodised. the salt packing says 40 ppm of potassium iodide is mixed with the salt. can anyone shed some light on it? thanks.

I can't think of anything except what Borek said... the amount of potassium iodide wouldn't have that effect anymore than dumping a load of sea salt into clear water would.
 
  • #17
Where did you get the carbon for the electrodes? I presume you scavenged it from somewhere, which could hint at what the contamination might be.
 
  • #18
mrjeffy321 said:
Where did you get the carbon for the electrodes? I presume you scavenged it from somewhere, which could hint at what the contamination might be.

Oh... if that's the case I'm going to be pissed... that up front would have answered a LOT.
 

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