Creating Na+ and Cl- out of saline

[Billy T]

Would performing electrolysis in mineral oil (CH) and sodium chloride beak apart the Na+ and Cl- ions, attracting them to the respective electrodes?

I doubt salt separates into + & - ions in oil, but have never tested that. Again as I told you earlier, post 11, there is no way you can get significant separation of + ions from the - ions in two different solutions - the electrical mutual attraction is too strong to permit that.

[Aqueous Id]

Would performing electrolysis in mineral oil (CH) and sodium chloride beak apart the Na+ and Cl- ions, attracting them to the respective electrodes?

The ions will concentrate around the electrodes in water. That was my reason for suggesting the video clip I gave you. Odds are, the ion concentrations will be substantially different in the two test tubes as long as the field is supplied. You would want to remove them quickly after removing power since they will start to equalize after that.

You can try oil. I suspect you will get no current flow since it's good insulator. I doubt that salt will dissociate into ions in oil. Here some tutorial info you might find useful:

http://www.northland.cc.mn.us/biolog.../dissolve.html

As you go through this exercise you will discover that it requires chemistry to understand what you are trying to accomplish. Sodium metal will react violently in chlorine gas, producing salt. They don't normally begin in the reaction in the "ionized" state as you may think, but as electrically neutral substances.

It might help if you explain why you are seeking the ionized states, since they are hard to deliver in product form.

[Billy T]

The ions will concentrate around the electrodes in water. ...

I think that is false - exactly the opposite will happen. The bulk of the solution will be electrically neutral with greater concentration of both ions than near the electrodes. Near the + electrode there will be LOWER concentration of Cl- ions than in the bulk of the solution as some have been converted in Cl2 at the electrode.

I.e. near the electrodes there is a concentration gradient - that is what causes there to be a net flux towards the electrode. Most of the voltage drop will be across this gradient. This is called the electrode polarization zone. In the electrode polarization zone, the electric field is stronger and sweeping the ever decreasing concentrations of ions towards the electrode where they are removed. Adjacent to the electrode the volumetric concentration ions may be less than half what it is in the bulk of the solution - the ions are being removed, only at the electrodes.

The stronger the electrode current density is the greater will be the gradient. Only when the current density is very low will the gradient be small and the electric field then be nearly uniform between the electrodes.

[Billy T]

... http://www.northland.cc.mn.us/biolog.../dissolve.html ...

One thing very nice about this link is that it does correctly show the two Hs of H2O on one side of the O AND that the negative O is next to the Na+ ion and conversely the Hs are next to the Cl- ion - all as I explained in post 12.

[pinecone]

I'm so happy at the many wonderful responses on this new thread... I wouldn't of imagined so many helpful people on this board!

To be clear on our objectives, we are tasked to find a solution that can be converted into two solutions, one with ions and one with anions (positive and negative charge). I'm a little stumped...

Aqueous, thanks for the excellent post. I'm definitely going to try that...it makes sense why there would be a bias of Cl- and Na+ in the test tubes because of the electric field. I wonder how large a field would affect the bias.

[Billy T]

... Aqueous, thanks for the excellent post. I'm definitely going to try that...it makes sense why there would be a bias of Cl- and Na+ in the test tubes because of the electric field. ...

Aqueous has misinformed you on several points. You should pay more attention to what I have told you. If you don´t want to accept my word, search a little about the electrical neutrality of ionic solutions. Here are first two sentences of my first Google hit:

"... In any macroscopic sample of any aqueous solution, the sum of all the positively charged ion concentrations always equals the sum of all the negatively charged ion concentrations. An aqueous solution is always electrically neutral. ..." From: http://www.acidbase.org/index.php?sh...e&id=12&sid=18

That is: In any volume bigger than 1 cubic mm, the number of + ions will differ from the number of - ions by less than 1 in a million! (that includes regions near the electrodes too)

Also it is wrong that the equal concentrations of + and - ions is greater near the electrodes - that is where, when current flows, the concentrations will be the LEAST! (You are removing ions there - for example Cl- concentration near the + electrode is dropping as Cl2 is being produced from that Cl- concentration. The Na+ concentration is dropping there too to maintain electrical neutrality of the solution. The mechanism that achives this is easy to understand: Imagine that it did not drop. Then there would be a huge, mutual repulsion between the excessive + charges (Those that exceed the - charge concentration.) This repulsive field would be thousands of times stronger than any man can produce, if the Cl- concentration near the electrode is only half what it is in the bulk of the solution - I.e. if for every Cl- there were 2 Na+ near the electrode.

You want to believe that you can with electric field separate the + from the - ions, but YOU CANNOT! Physical facts do not conform to your wishes, but to the laws of physics. If you could by magic make 1 mm cubic liquid with only one sign of charge - you would have a very powerful electrostatic bomb when the magic turned off. Hundreds of time more powerful than same mass of TNT, I am sure.

[pinecone]

Okay, sounds good. Many thanks for the education Billy .

Is it possible to make a liquid positive or negative in any way? That's what we're tasked. This forum is extraordinary!

[Billy T]

Okay, sounds good. Many thanks for the education Billy .

Is it possible to make a liquid positive or negative in any way? That's what we're tasked. This forum is extraordinary!

Answer depends upon what you mean by "a liquid positive"

Yes you can make it positive wrt other points that are more negative. For example set metal can holding the liquid on top of a Van de Graph machine would make it 10s of thousands of volts positive wrt the rest of the room.

If you mean make it have 1% or more positive ions in it than negative ions in it, no.

[Aqueous Id]

I think that is false - exactly the opposite will happen. The bulk of the solution will be electrically neutral with greater concentration of both ions than near the electrodes. Near the + electrode there will be LOWER concentration of Cl- ions than in the bulk of the solution as some have been converted in Cl2 at the electrode.

In less time than we can analyze it, pinecone can implement it. But then what? What next steps does pinecone have in mind? I'd like to flush these out, since the question in the OP is essentially moot, given the conversation thus far.

Given the depletion of ions that evolve, the ones that remain would be locally in excess as long as current flows. There's a lag in diffusion of H⁺ and OH^- to replenish the amounts given up in reaction with them. That lag causes some buildup. Thus electrical neutrality is preserved over the entire volume, but not so locally. A pH test of the two tubes will show they've differentiated into acid and alkaline. This would account for NaOH and HCl concentrations in each, but for "a while" the Na⁺_(aq) and Cl^-_(aq) concentrations should be imbalanced. The inverted test tubes offer a little isolation and the turbulence from the electrodes ought to allow some of the excess ions to accumulate in them.

This is a very crude process, but a good first step for a beginner. It offers a gateway to the more serious kind of investigation that would invariaby involve some actual chemistry.

[Billy T]

...Thus electrical neutrality is preserved over the entire volume, but not so locally.

No read the quote from the literature I gave again. it starts: "In any macroscopic sample of any aqueous solution, ..." I made that a little more specific by saying in any volume of 1 mm cubic or greater.

...A pH test of the two tubes will show they've differentiated into acid and alkaline.

pH is not a measure of ion concentrations, only of the H+ ion concentration. Neither the literature nor I am saying that the number of Na+ ions must equal the number of Cl- ions. I only said that the difference between + and - charge in any volume (with or without current flow) is less than 1 part in a million if the volume is 1mm^3 or greater.

... The inverted test tubes offer a little isolation and the turbulence from the electrodes ought to allow some of the excess ions to accumulate in them.

yes the mix of ions that achieve charge neutrality can be different in the two test tubes, but no net charge in either. (again equality to an accuracy of at least 0.000,000,1)

...This is a very crude process, but a good first step for a beginner. It offers a gateway to the more serious kind of investigation that would invariaby involve some actual chemistry.

Yes if he is aware of the dangers, especially of inhaling any Cl2 then I too encourage him to play around but think he should used a mild acid (Or even sodium hydroxide but that too is dangerous to the skin with contact) not NaCl to make the water more conductive when passing DC thru it.

I would prefer he use copper sulfate to plate copper on a nail etc. It is a very pretty blue solution that can not injure him and quite cheap, but not as cheap as salt is.