# Determining completion of electrolytic process

1. Jul 17, 2007

### JGM_14

if one were to electrictally produce Cl from salt solution how would you tell when all the salt was electroliticaly converted to NaOH and Cl2?

2. Jul 17, 2007

### mrjeffy321

Is this a theoretical question or a practical one?

Theoretically, you could collect the Chlorine gas as it bubbles out of solution and measure its volume. From this, you could obtain the number of moles of Cl2, and from this the amount of Chloride salt consumed in the reaction.

In practice, it is more difficult than this since some of the Chlorine gas will dissolve in solution and produce Hypochlorous acid (HOCl) and take part in a reaction which will yield a Chlorate salt. So in practice, you will end up with (assuming you started out with NaCl) a solution of Sodium Chlorate (and some other stuff), it will not all work out perfectly to be NaOH and Cl2. Of course, the pH of the solution and the conditions which the solution was electrolysized under will effect just how much Sodium Chorate will be produced as opposed to just letting the Chlorine gas escape into the atmosphere.

3. Jul 19, 2007

### JGM_14

it is a more practical question than a theoretical question
different question:
if one were to electrictally produce iodine from potassium iodide, ect.

4. Jul 19, 2007

### mrjeffy321

What is the question? Same as before, just with KI instead of NaCl?

Lets see….how would I do it if I wanted to do this…..
I would probably measure the total charge (Q = I * t) which I have passed through the cell over the period of time I had been electrolysizing the solution at some assumed efficiency. I could write the electrochemical reaction occurring and from this determine how much charge is needed to produce X number of moles of I2.

To do this simply, one could just use an Amp Hour meter….but these meters are not that common I have found (nor cheap). A more complicated solution would be to take periodic measurements of the current through the cell and manually calculate the total charge passed through.
Or if you have access to some constant-current supply, that would be even better since you wouldn’t need to keep checking the current, you would just need to measure how long it has been running.

5. Jul 20, 2007

### Cesium

Periodically, check it with litmus paper. Chlorine bleaches it.

6. Jul 21, 2007

### JGM_14

sounds too complicated (i was never good at math, calculator wonderful invention)
Couldn't you just stop it when the desired stops being produced and measure it from there?

Would seperating the two electrodes with a salt bridge yeild a pure solution of, say iodine and KOH

7. Jul 21, 2007

### JGM_14

i have no litmus paper.

8. Jul 21, 2007

### Cesium

Well you could buy some cheaply or....use something else that chlorine bleaches...do some searching around. I know it bleaches some flowers, http://mattson.creighton.edu/Cl2/index.html" [Broken], and fabrics! I've never done experimenting with this so I can't tell you how fast you will see a change, but I'm sure you can get some info easily on this. There's got to be something lying around in your house that will work!

How precise does this have to be? If all else fails, you can just keep on running the electrolysis until you can't smell any more chlorine gas. This might be hard though because it would be difficult to distinguish the chlorine gas smell from the bleach smell of the sodium hypochlorite that is formed.

Last edited by a moderator: May 3, 2017
9. Jul 23, 2007

### JGM_14

could you make oxygen from co2 by electrolysis
sodium hypochlorite solution can be degassed in a vacuum dessicator
the link was very informative, thanks

10. Jul 23, 2007

### Gokul43201

Staff Emeritus
Do you actually intend to perform an electrolysis? Which one is it - NaCl or KI? What do you wish to produce? What are your requirements on purity and quantity (i.e., what is the end use)?

The differences between the two experiments are so many that it would make little sense to sit about discussing electrolysis of NaCl, if you wish to electrolyse KI instead, or vice versa.

11. Jul 23, 2007

### Cesium

Electrolysis of gaseous carbon dioxide? I don't see how that would work.

You can produce oxygen by electrolyzing water with some stable electrolyte like sulfuric acid or sodium hydroxide. Oxygen is produced at the anode (+) and hydrogen is produced at the cathode (-). Of course, you can also produce oxygen through a variety of non-electrochemical methods.

12. Jul 24, 2007

### JGM_14

i just want something to apply to my current or future experements.:grumpy:

liquid co2

Decomposition of H2O2 yeilds oxygen with potassium iodide catalyst

13. Jul 24, 2007

### Cesium

not easy to make at home and I doubt it'll conduct electricity too well

Last edited: Jul 24, 2007
14. Jul 24, 2007

### Gokul43201

Staff Emeritus

15. Jul 24, 2007

### JGM_14

well i was just wondering if one could electroplate carbon onto a stainless steel electrode for making chlorine,i know it is easier to buy them but i am not a person with alot of money, or any for that matter
I might do an experement on how different gases effect plant growth seed germination but i need an airtight container like a bell jar
will oxygen react with materials that are wet or damp, like catch on fire (doubt it)i knowas theoxygen content increases the autoignition temprature goes down
i did something like this in school, we did a lab on seed germination i put argon in a bag with a wet paper towel with durum seeds wraped in it i did the same thing with pure oxygen and somthing strange happened both germinated extremely fast like in 2-3 days and in the oxygen bag the coteledon appeared first the control didn't germinate at all (because someone watered it too much, they just rotted) i want to replicate this experement and test the growing rate, growing time, water consumption(don't know how i will measure it, though), and changes in the reproduction of the plant. Durum is easy to grow and i have about half of a five gallon pale full of the seeds. does anyone have any questions comments or ideas,any idea is welcome, even the stupedist idea can spark the best ideas.

Last edited: Jul 24, 2007
16. Jul 24, 2007

### Moonbear

Staff Emeritus
Chlorine gas is extremely poisonous. If that is your intent here, I'd STRONGLY advise against this. It won't take much to kill you. It'll kill your plants too.

Now, a few other possibilities you should consider, especially if you replicate your results of the controls rotting while the others germinate...you may not be affecting germination rates at all (do you have a way to get sterilized materials for your experiment...everything from the paper towels and soil you're using to the containers it's being put in? Maybe your school has an autoclave they will allow you to run your supplies through?)...you may only be hindering rotting. You may have deprived the fungus or bacteria that is rotting the seeds of something they needed in ambient air to grow faster than the wheat seeds by diluting out the ambient air with your other "pure" gases. (How pure were they?) The best way to test this is to compare your results with ambient air as you previously set them up with results obtained from an identical set-up with the exception of everything being sterilized first...unfortunately, I don't know of a way to sterilize your seed without killing it, so if the contaminant is on the seed itself, you're not going to be able to rule that out).

So, to embark on your scientific journey, I recommend being very careful about analyzing your previous results, and looking for flaws in the design and possible explanations other than the experimental treatments first, making sure you can replicate the original experiment, and only then considering how or why what you did might work rather than heading off on a very unfocused approach (the type of experiment you're proposing above is what those of us in research call a fishing trip...it's less of an hypothesis-driven experiment, and more of a "let's throw everything at it and see if anything sticks" approach, which often leads nowhere productive).

17. Jul 27, 2007

### JGM_14

i think that this experement may have to wait until i get better materials
the concentration of the chlorine wasn't going to be very high, like a plant growing in the same room as an indoor pool, around 6-7 ppm,just enough so it is noticible. I am fully aware of the dangers of chlorine. i am not one of them people that just do with out research, usually they don't live very long, i do lots of reasearch before i go experementing, but thanks for the concern.
Will a mild bleach solution harm the seeds?

18. Jul 27, 2007

### chemisttree

Place an HTH pool chlorination tablet into a jar of water to generate this level of Cl2. How will you measure 6-7 ppm Cl2?

If it is mild enough and for a short enough contact time there should be no problem. I assume that you are going to use Duram wheat? Are you using seed stock or some stock that had been harvested? You need to establish a baseline germination rate before you begin. Seed stock is often treated with insecticide or fungicide. How will a reactive gas like Cl2 interact with any seed coating product? How will you translate the exposure condition(s) from a lab environment into the field?

19. Jul 27, 2007

### JGM_14

it is a harvested stock there could be a possible bleaching of the seed, also make the water slightly acidic by the formation of hypochlorus acid and possibly HCl which may react with some herbicides, insecticides, and fertalizers

20. Jul 27, 2007

### chemisttree

Harvested stock is of unknown quality related to the germination rate. You must determine that first. There is no seed coating so no need to worry about the interactions.