Electrolysis of Sodium Chloride Solution

Hi mupwi,

It may be iron chloride from impurities in the tap water. Try using distilled water and see if you still get the ppt.

Mike

There are enough contaminants in tap water (in your case probably iron from the pipes) that they will oxidize and really make a mess. Also make sure your conductors (unless they are stainless as well) are not in contact with the solution. You might find a chemical analysis of the seawater in the area you plan to do this and study the elctrochemistry of the dissolved chemicals to make sure you don't end up with something you don't want. I would assume a constant flow of seawater would prevent the build up of any precipitates.

What kind of voltage and current density are you using? What are you using for a power supply? If your voltage is too high, you will waste a lot of energy and generate a lot of heat. I'm not familiar with your terminology, can you clarify what you mean by mhd device? I might be able to give you some more pointers.

One other thing...are you conducting your experiments in an inert container such as glass?

Actually sea water also includes fairly high concentration of Magnesium Sulphate, so you may want to also add "epsom salt" to the electrolytic solution - that should given you more realistic simulation results.

Googles might help you with the percent concentrations, I do not remember. Good luck

yea go to a salt water fish store and get sea salt from there also you will need a saltwater PH meter and a TDS meter (total disolved solids ) it measures the specific gravity to get the results and find out, if your testing for local conditions, what the makeup of your area sea water is, there is a difference between atlantic and pacific sea water,as well as the many seas.

mhd is magneto hydro dynamic it is a device for pumping conductive liquidsusing the same forces involved in morors just the wire in the windings are replaced by the conductive liquid creating a pump with litle to no terbulance in the flow and no impelers to get jamed, imbalances or cloged this tech is used currently to pump molten aluminium in some smelters and on a few experimental boats and submarines.

I am trying to recreate this device in my workshop for 2 perposes one is to build a troling "motor" with this technowlogy that I think would just be cool and for another perpos that I will not discuss here as I think it could have some comertial merit

to awnser some of youre questions the only conductors in contact with the water is the stainless.

at the moment I am operating it on 5v as the only spare power supply I have at home at the moment is an old pc power supply the final device I plan to run on 2v

we have verry clean water in our city but you may be right that there might be some contamination efecting the reaction but what concerns me is many people have salt clorinators for there pools in the area but dont have this percipitate could it be fron the the fact that I used iodated table salt instead of pure salt this just came to me as I was typing

Thanks mupwi I have played with MHD for years on paper.

A few suggestions: don't reuse your brine solution very much because it will become full of impurities giving you false data; As your working fluid accelerates the cross section of your nozzle will need to decrease or you will have the drag of negative pressure up stream slowing your exhaust velocity; Use plastics and or glass for everything the brine touches and a thin coating of epoxy paint in your motor to help stop your working fluid from being contaminated.

Sounds very interesting please keep me/us updated.

Brad

Ahhh....Magnetohydrodynamics....Sound like a problem out of Jackson...

So you are moving the fluid. I assume you don't want electrolysis to take place with this application. Dropping the voltage to 2 volts is a good start, but you will probably need more current than a PC power supply will provide. Have you tried using NaOH as an electrolyte for experimentation? I know it's not the fluid you will be working with ultimately, but it may help you fine tune some of your components.

Have you had any success yet? It sounds really cool.

I see you're from Durbs - try & use real sea water, get a friend to cart a few 20l buckets or drums to where you are experimenting.

I wanted to say that the bass fishermen would be interested in a nice, quiet MHD trolling motor, but locally they are mostly inland in fresh water. Shucks.

Hello mupwi,

Check these videos out. They are very simple experiments, working with salt water. It explains as it goes on what the different colour represent.

This first site will explain what the colour you have is, Iron. The iron content looks green, but turns an orange colour when left standing.

• Colourful electrolysis - Experiments - Practical Chemistry An interesting introduction to the electrolysis of brine (sodium chloride solution). Students use Universal Indicator to help them follow what is happening ...
  www.practicalchemistry.org/experiments/colourful-electrolysis,54,EX.html -
• Electrolysis of Aqueous Solutions - Part 1 of 3 Electrolysis of Aqueous Sodium Chloride. Play movie (QuickTime 3.0 Sorenson, duration 8 seconds, size 580 K). Electrolysis of a sodium chloride solution ...
  jchemed.chem.wisc.edu/JCeSoft/CCA/CCA3/MAIN/ELECSOL/PAGE1.HTM - 25k - Take care........................

Out of fascination with the subject, my students and I fired up the lab power supply, put a styrofoam cup on top of a neodymium magnet used paperclips for electrodes and got a really nice swirling vortex of briney MHD terror!

Thanks for the post! It led to a really nice discussion on lorentz forces and the application therein!

BTW: it didn't take long for the paperclips to oxidize and make a mess. However, the green stream of oxidation really showed the movement of the fluid.

Sea water contains numerous dissolved elements and trace materials that may (or may not) effect your results. Durban is right on the coast, have you tried using samples of the sea water directly to get more accurate results?

Nothing beats the real thing, and there is a lot of it freely accessable.

You could also try using platinum electrodes with the solution instead of stainless steel. This way you have ruled out all possibilities.

The brown stuff is probably oxides of various metals like iron, to be found usually as dissolved substances in the water.