Electrolysis questions

[radonek]

Dunno about how to do it right, but I do know how to do it wrong. I don't want to sound all panicky, in fact, I had electrolyzing as part of toy electrical set as a child and survived :-) But you mentioned going after an engine, and that wont fly without producing and storing a nontrivial amount of propelant.

[DoctorDavinci]

On the topic of voltage in regards to electrolysis .....

The voltage required to split the water molecule ranges from around 2.8v down to 1.4v depending on the electrical conductivity of the water ... pushing more than this through the water is a waste of energy as the voltage is just the push and the current is what is doing the work of splitting the water molecule (so technicall you should easily be able to run 3 anode/cathode pairs in parallel using a 9 volt battery)

There also is the matter of being able to catch the hydrogen and oxygen ... to do this get two thin pieces of metal and sloder wires to them at one end (be sure to have one black and the other red), then get yourself some polyester fabric and make a bag to go around one of the pieces of metal with a hose coming out of it (you can sew it together or even use gorilla glue) ... the type of metal doesn't matter allvthat much unless you're trying to be efficient in your electrolysis ... also take some sandpaper or emery cloth and score up the metal as this will create more surface area 

Then sandwich the two pieces of metal together and submerge in the water.

What will happen is the 'bagged' anode/cathode will have its bag fill up with gas while under water (like when you jump into a pool with wet shorts on, you always get air pockets in your shorts) and if you have the hose connected to a bag it will fill up with gas ... what this gas will be is determined by which polarity you decided to connect that side of your gas generator to

IIRC hydrogen is attracted to the positive and oxygen is attracted to the negative 

As for safety ... when playing with hydrogen there is always a risk of explosions, you have been warned 

Edited January 18, 2017 by DoctorDavinci

[munlander1]

40 minutes ago, radonek said:

toy electrical set as a child and survived :-)

Toy chemistry sets used to have uranium in them

39 minutes ago, DoctorDavinci said:

The voltage required to split the water molecule ranges from around 2.8v down to 1.4v depending on the electrical conductivity of the water ... pushing more than this through the water is a waste of energy as the voltage is just the push and the current is what is doing the work of splitting the water molecule (so technicall you should easily be able to run 3 anode/cathode pairs in parallel using a 9 volt battery)

 

Could you explain this more? Thanks for the idea about capturing hydrogen.

[DoctorDavinci]

4 minutes ago, munlander1 said:

Could you explain this more? Thanks for the idea about capturing hydrogen.

Unfortunately I have said as much as I am willing to on this subject ... However, I can direct you to a couple links that may shed some light on what I have said so far:

https://en.wikipedia.org/wiki/Electrolysis_of_water
https://en.wikipedia.org/wiki/Oxyhydrogen

I also suggest looking into electricity and how it it used to perform work, specifically DC electronics ... the anode/cathode pair I mentioned can be considered as a resistor when placed in water which, when a DC current is passed through it, creates what is called Brown's Gas (Oxyhydrogen)

Good luck with your experimenting, but please be sure to get safety equipment and learn as much information as you can before attempting to create your own generator ... I've seen a few engines go up in smoke because of not being as informed as we should have been

[munlander1]

3 minutes ago, DoctorDavinci said:

Good luck with your experimenting, but please be sure to get safety equipment and learn as much information as you can before attempting to create your own generator ... I've seen a few engines go up in smoke because of not being as informed as we should have been

Thank you! I have not done anything after the day of my first in this thread, mainly supplies and a small part of safety and execution. I am years away from a rocket engine, at least one made to provide significant thrust.

[DoctorDavinci]

3 minutes ago, munlander1 said:

Thank you! I have not done anything after the day of my first in this thread, mainly supplies and a small part of safety and execution. I am years away from a rocket engine, at least one made to provide significant thrust.

Yeah, your not going to get a rocket going using electrolysis of water to create your hydrogen ... sorry, but that is just not gonna happen

Do some hard research and you will see why I say this ... you just can't generate enough to make it work without storing the hydrogen which is where you run into many serious and potentially life threatening issues as it is very unsafe to store hydrogen unless you have PROPER EQUIPMENT designed specifically for this task

Here, read this: https://en.wikipedia.org/wiki/Hydrogen_storage

[steve_v]

13 hours ago, radonek said:

…and be mindful of consequences.

Dude, industrial rig running 6 thousand amperes. That failure mode is just not possible with a few 9v batteries.

22 hours ago, p1t1o said:

Manipulating a large bag of hydrogen-mixed-with-how-much-air with a string of 9V batteries sparking in the background...

I would suggest keeping the bag small. I've not tried it with hydrogen, but I know someone who blew out all the windows in one side of a house with a garbage bag of acetylene/oxygen mix. Not smart. A bread bag of oxy/acetylene on the other hand...

Hydrogen isn't as energy dense as most other fuel gasses, but it has a very broad explosive range, so be careful with it.

[Steel]

7 hours ago, DoctorDavinci said:

Yeah, your not going to get a rocket going using electrolysis of water to create your hydrogen ... sorry, but that is just not gonna happen

Do some hard research and you will see why I say this ... you just can't generate enough to make it work without storing the hydrogen which is where you run into many serious and potentially life threatening issues as it is very unsafe to store hydrogen unless you have PROPER EQUIPMENT designed specifically for this task

Here, read this: https://en.wikipedia.org/wiki/Hydrogen_storage

Not only is it extremely dangerous to store hydrogen, but as far as I can see the only established methods for storing it involve either getting it to 350 times atmospheric pressure or down to 20 K.

[p1t1o]

12 hours ago, munlander1 said:

So what are the risks of what I am doing? What safety procautions do I need to take? 

 

9 hours ago, DoctorDavinci said:

There also is the matter of being able to catch the hydrogen and oxygen ... to do this get two thin pieces of metal and sloder wires to them at one end (be sure to have one black and the other red), then get yourself some polyester fabric and make a bag to go around one of the pieces of metal with a hose coming out of it (you can sew it together or even use gorilla glue) ... the type of metal doesn't matter allvthat much unless you're trying to be efficient in your electrolysis ... also take some sandpaper or emery cloth and score up the metal as this will create more surface area 

Then sandwich the two pieces of metal together and submerge in the water.

What will happen is the 'bagged' anode/cathode will have its bag fill up with gas while under water (like when you jump into a pool with wet shorts on, you always get air pockets in your shorts) and if you have the hose connected to a bag it will fill up with gas ... what this gas will be is determined by which polarity you decided to connect that side of your gas generator to

 

Just a quick one: Im not sure if Im understanding this correctly, but just to be sure - if you collect the gas from both electrodes into the same container you will be collecting a perfect stoichiometric mix of hydrogen and oxygen which is just begging to explode - DO NOT DO THIS - keep hydrogen and oxygen separate.

 

Edited January 18, 2017 by p1t1o

[Dafni]

4 minutes ago, p1t1o said:

 

 

Just a quick one: Im not sure if Im understanding this correctly, but just to be sure - if you collect the gas from both electrodes into the same container you will be collecting a perfect stoichiometric mix of hydrogen and oxygen which is just begging to explode - DO NOT DO THIS - keep hydrogen and oxygen separate.

 

Still needs a source of ignition, but the tiniest spark would do it of course. If you are carefull you can store this so called oxyhydrogen (stochiometric mix of H2 and O2) in a balloon or a bag for short periods of time, for example to demonstrate its potency to students or whatever. Quite a common classroom experiment back in my days.

[p1t1o]

Just now, Dafni said:

Still needs a source of ignition, but the tiniest spark would do it of course. If you are carefull you can store this so called oxyhydrogen (stochiometric mix of H2 and O2) in a balloon or a bag for short periods of time, for example to demonstrate its potency to students or whatever. Quite a common classroom experiment back in my days.

Thats the thing, about the only thing you *can* do with a bag of this is explode it.

[magnemoe]

10 hours ago, munlander1 said:

Thank you! I have not done anything after the day of my first in this thread, mainly supplies and a small part of safety and execution. I am years away from a rocket engine, at least one made to provide significant thrust.

Coolest use of some liter of hydrogen is probably as lifting gas in an balloon. 

One easy way of gathering gases from electrolysis is to fill an bottle with water then put it upside down into the water container used for electrolysis, water will stay in bottle until it start filling up with generated gas, this will remove the water so you container will overflow so make sure to handle this. 
You will need some sort of stand to hold the bottle and probably an small funnel to make sure all gas enter the bottle. 

[PB666]

On 1/11/2017 at 3:41 AM, p1t1o said:

Heyho, just a note - you are describing electrolysis, electrophoresis is where you use a potential difference to draw substances through a medium, usually a gel, to separate them by molecular weight, similar to chromatography. (Electrolysis usually occurs during electrophoresis as you are putting a voltage through a carrier solution)

You're thread drew my eye because I was once a student LabTech whose main job was running electrophoresis experiments. I earned the nickname "The Gel King" because I could run 4 machines at once

The "gunk" you get with electrolysis I think are agglomerations of various insoluble oxides, probably from the electrodes, but also possibly from interactions with various ions in the water depending on how "hard" it is.

Obviously never drink anything...hopefully you just typed that to head off paranoid readers!...good practice is not to eat or drink anything anywhere near your experiments, get a white coat,a box of rubber gloves and some goggles. Its not just to look the part, even with innocuous chemicals and reactions, this is the minimum PPE for almost any chemistry.

In any case, the gunk is probably not that toxic, maybe irritant at most so you dont want it on your skin or in your eyes (plus none of this discussion is *proof* that it is safe), you may be changing the pH of the solution as well. Basically in chemistry *always* avoid contact with your reagents/reaction. And if for some reason you do decide to scale this up significantly, production of gases like chlorine or hydrogen could become a concern, so if you do, do it outside. You should definitely do it in a ventilated area in any case.

To get cleaner electrolytic reactions, you need to use laboratory-grade reagents, ultra-pure water (Kitchen filter will not help much. Try distilled water if you can make or preferably buy any) and electrodes made of something like carbon (graphite) or platinum. Pencil lead could work if you can get workably large pieces or you might be able to get graphite electrodes from a radioshack equivalent.

 

Probably was not using a pure platinum electrode.

The biggest health risk around an electrophoresis apparatus is the risk of electric shock, secondarily the unknown risk of using ethidium bromide for agarose gel polynucleotide separation.

Anyway if you have been using an old agarose gel apparatus it can also be oxidants of EtBr which have a yellowish/brown color.

[p1t1o]

10 hours ago, PB666 said:

Probably was not using a pure platinum electrode.

The biggest health risk around an electrophoresis apparatus is the risk of electric shock, secondarily the unknown risk of using ethidium bromide for agarose gel polynucleotide separation.

Anyway if you have been using an old agarose gel apparatus it can also be oxidants of EtBr which have a yellowish/brown color.

Its ok, there was a small mistake, the OP is discussing electrolysis, not electrophoresis

[munlander1]

Thanks for clearing that up. I did edit my first post and it contains the correct terms now.

Edited January 19, 2017 by munlander1

[Hannu2]

On 18.1.2017 at 2:49 AM, munlander1 said:

Toy chemistry sets used to have uranium in them

Could you explain this more? Thanks for the idea about capturing hydrogen.

 

Uranium is relatively undangerous if you do not dissolve it and drink to grind it to dust and inhale. Hydrogen is much more dangerous.

Breaking of water molecule needs exactly 2 electrons, which have certain energy. Energy of an electron depends on voltage and number of electrons depends on current. So you want to as low voltage as possible and as high current as practical. If you increase voltage all excess energy heats the electrolyte and causes it to boil and spread poisonous and/or corrosive aerosols everywhere.

You can increase current by using electrolyte and suitable electrode geometry. You can find details if you want, but please understand that even cheap and simple hobby electrolyser produces easily enough hydrogen to explode your house and kill everyone inside. Hydrogen is nasty stuff even for professional users, which have strict safety measures. There are million more safe and as interesting chemicals for hobby chemist, even for pyrotechnical experiments.

[Steel]

I think the general theme of this thread is that unless you are really careful, hydrogen is not something to be messed with! 

If making a small rocket engine is what you're after there are far better fuels to start off with, see this thread for example:

http://forum.kerbalspaceprogram.com/index.php?/topic/126932-ksp-inspired-me-to-design-a-liquid-fueled-rocket-engine/

[Hannu2]

Hydrogen is probably the second most stupid idea as a propellant for a hobby rocket engine (the most stupid must be fluorine and its compounds). Hydrogen's density is so low that only way to get sane amount into burning chamber is to use liquid hydrogen. Liquefaction is practically impossible as a garage project (because probability of exploding the garage before success is exactly 1).

[shynung]

36 minutes ago, Hannu2 said:

Hydrogen's density is so low that only way to get sane amount into burning chamber is to use liquid hydrogen. Liquefaction is practically impossible as a garage project (because probability of exploding the garage before success is exactly 1).

As an addition, liquefying hydrogen requires cooling it to 20 K or -253 ^oC. This is difficult; liquid nitrogen's boiling point is 77 K, which is much warmer than that of hydrogen. The liquefaction equipment won't be cheap.

Also worth mentioning is the fact that liquid hydrogen can and will leak out no matter how tight the plumbing, because the hydrogen molecules are small enough to slip in between the molecules comprising the tank.

On top of all that, hydrogen burns without a visible flame. One can walk into a hydrogen fire without noticing it until they start to feel the heat. @munlander1, however you choose to store hydrogen gas, keep an IR fire sensor handy.

[munlander1]

On January 18, 2017 at 3:38 AM, steve_v said:

Hydrogen isn't as energy dense as most other fuel gasses, but it has a very broad explosive range, so be careful with it.

So there is not a big(energy wise) explosion, it take place in a big space though.(Am I right?

On January 18, 2017 at 3:38 AM, steve_v said:

I would suggest keeping the bag small. I've not tried it with hydrogen, but I know someone who blew out all the windows in one side of a house with a garbage bag of acetylene/oxygen mix. Not smart. A bread bag of oxy/acetylene on the other hand...

How should I store this? 

16 hours ago, Hannu2 said:

Uranium is relatively undangerous if you do not dissolve it and drink to grind it to dust and inhale.

Kids are some what prone to eating things though.

16 hours ago, Hannu2 said:

 

Breaking of water molecule needs exactly 2 electrons, which have certain energy. Energy of an electron depends on voltage and number of electrons depends on current. So you want to as low voltage as possible and as high current as practical. If you increase voltage all excess energy heats the electrolyte and causes it to boil and spread poisonous and/or corrosive aerosols everywhere

So would you recommend I use a smaller battery? Like a aa over a 9v?

16 hours ago, Hannu2 said:

but please understand that even cheap and simple hobby electrolyser produces easily enough hydrogen to explode your house and kill everyone inside

How long would I have to let it run for?

16 hours ago, Steel said:

 

If making a small rocket engine is what you're after there are far better fuels to start off with, see this thread for example

Thanks for the thread link!

16 hours ago, Hannu2 said:

stupid must be fluorine and its compounds

Tries clorine trifloride* 

16 hours ago, Hannu2 said:

Hydrogen's density is so low that only way to get sane amount into burning chamber is to use liquid hydrogen. Liquefaction is practically impossible as a garage project (because probability of exploding the garage before success is exactly 1).

If I do make one, I don't think I will put it on a rocket because of the faa's restrictions and stuff. That stuff is in the future though.

 

15 hours ago, shynung said:

As an addition, liquefying hydrogen requires cooling it to 20 K or -253 ^oC. This is difficult; liquid nitrogen's boiling point is 77 K, which is much warmer than that of hydrogen. The liquefaction equipment won't be cheap.

Also worth mentioning is the fact that liquid hydrogen can and will leak out no matter how tight the plumbing, because the hydrogen molecules are small enough to slip in between the molecules comprising the tank.

On top of all that, hydrogen burns without a visible flame. One can walk into a hydrogen fire without noticing it until they start to feel the heat. @munlander1, however you choose to store hydrogen gas, keep an IR fire sensor handy.

I don't plan to liquidfy it. Because of the cost alone I am not gonna pay to keep hydrogen at those insane temps. Would an ir heat gun work fine?

 

So are there any safety hazards with working with oxygen besides breathing too much oxygen?

 

I would like the take a moment to address all of you people who have responded to my thread, thank you!

[shynung]

42 minutes ago, munlander1 said:

Would an ir heat gun work fine?

Only if you have someone else constantly scanning the rig, the experimenters, and the surrounding areas.

Basically, you don't want to be in a situation where a fire can start without you knowing about it. That means good ventilation, minimizing electrical sparks including statics, avoiding using flammable tools and materials, and good safety procedures above all else. That includes what to do when disaster strikes.

[Steel]

4 hours ago, munlander1 said:

So are there any safety hazards with working with oxygen besides breathing too much oxygen?

In high enough concentrations it will make things like metal and plastics (I.e. things you wouldn't normally think would catch fire) highly flammable, which is particularly nasty.

[Hannu2]

3 hours ago, munlander1 said:

So there is not a big(energy wise) explosion, it take place in a big space though.(Am I right?

Probably you are right, energy wise. But in this case you should think safety wise. Even small hydrogen explosions are very severe safety risks for health and material at typical house environment. Hydrogen is extremely sensitive to explode and it leaks very easily, also through the walls of tubes and containers. You can find pictures from "small" hydrogen explosions, for example battery recharge failures. You do not certainly want such "small" explosion in your home or be near if you are outdoors.

You should not store hydrogen for a long time. Small balloons, plastic bottles and plastic bags etc. are best containers for hydrogen. And when you stop your experiments you burn or release all hydrogen.

4 hours ago, munlander1 said:

So would you recommend I use a smaller battery? Like a aa over a 9v?

How long would I have to let it run for?

I recommend small adjustable power supply. Something like 3-12 V 1 A cost few tens of euros (or dollars). Electrolysis needs much energy and batteries are too weak and expensive. If you think batteries are more safe use rechargeable NiMH batteries. 2 or 3 cells in series should give suitable voltage. Be sure that you never short circuit rechargeable batteries (for example if your container breaks). They give very high current which can heat cables to red glow and ignite insulation or nearby materials (and of course hydrogen). Use fuse (for example 5 A) as near battery pole as practically possible.

It is impossible to give exact times for electrolysis. You should begin carefully with dilute electrolyte and low current and then monitor current, gas flows and warming during process. They change due to reactions on electrodes. Increase current gradually if you are very sure that you equipment can handle it safely.

4 hours ago, munlander1 said:

So are there any safety hazards with working with oxygen besides breathing too much oxygen?

I do not want to sound custodial, but questions like this make me worry. Oxygen is very reactive gas. Everything ignite very easily or even spontaneously (many common oil products) in high concentration oxygen atmosphere, and fires are insanely intensive. And guess what happens if oxygen replaces air between fibers in your clothes and static electricity makes a small spark.

If you have a job in which you have to handle oxygen or any other chemicals you have to get suitable safety training. Professionals have to use special tools and infrastructure which are specified to be used with those chemicals they need. It is for good reason. Almost every chemical has its own insidious risks which are often hard to see if chemical is not toxic or if it is necessary for living, like oxygen. If you make hobby experiments you should use Google to find safety information about any chemicals you intend to use and also any reaction products. Material safety datasheets are public data easily available and there are often other safety material for those who work with chemicals. And after that it is always better to play safe. Keep amounts small, reaction rates low, voltages low, work outdoors etc. And think what you do if accident happens before you begin your experiment. How do you extinguish fires without getting electric shock or pouring hot corrosive electrolyte on your clothes. Where do chemicals flow if electrolysis container breaks (because explosion or heat). How do you keep hydrogen and electrolytes away from your electric devices, which I think are not expensive professional models which are specified in explosion or fire hazardous environments. What happens if there will be short circuit which produces sparks, heat and overload to our power supply? Etc.

[steve_v]

6 hours ago, munlander1 said:

So there is not a big(energy wise) explosion, it take place in a big space though.(Am I right?

Less energy, yes. By explosive range I mean explosive at a wide range of concentrations - roughly 18-60% in air. Hydrogen also has a fairly low ignition energy, so a small spark is all that is required to ignite such a mixture.

6 hours ago, munlander1 said:

How should I store this?

Don't. Make a little, make it go pop, move on. You won't generate enough to run a rocket, and I can't really think of any other use for it.
A small quantity of hydrogen (and only hydrogen) might be stored in a plastic bag or balloon for a short time (it will leak through many plastics anyway), but storing larger quantities or for longer periods is highly dangerous and requires specialised equipment.

6 hours ago, munlander1 said:

So are there any safety hazards with working with oxygen besides breathing too much oxygen?

Many. Pure oxygen will make things that normally won't burn a serious fire hazard, and things that normally burn explode. Again, fine in small amounts, but don't try to manufacture or store it in quantity at home.

All in all, a small electrolysis experiment is fairly harmless, just keep volumes small and your work area well ventilated.

Edited January 20, 2017 by steve_v
Braindead editor mangling links.

[mrmeister]

http://www.treehugger.com/renewable-energy/hydrogen-powered-toy-rocket.html

For reference.

I didn't see anyone mention hearing protection. It's important for this.

A little hydrogen goes a long way in terms of accidentally destroying things. A beakerful might go foom, but an erlenmeyer might shatter. We had a guy doing demos with balloons when I was in school. A standard party balloon full of hydrogen explodes with enough force to really feel it all over from ~100ft away, if memory serves. That h2 o2 mix is remarkably louder still. 

Hydrogen also burns with an invisible flame, so if you have a leak, and it catches, you might not realize it before something bad happens.

Oxygen Hazard, people are quite right that pure oxy makes fires worse incredibly rapidly, and starts them where you might not expect, but isn't toxic. HOWEVER. Industrial oxygen (what you get if you buy a tank meant for welding rather than breathing) can have a terrible mix of random industrial nastiness in it. It burns fine, so no one cares, but breathe enough and it can be very unpleasant. (My lungs hurt for a couple days.) That's why medical oxygen is sold differently and costs more.

I don't know what scale rocket you were thinking of, but solid propellants are better once you get past soda bottles as pressure vessels. At which point, let me say you need to read a lot from people who are doing exactly that, since they have the experience. Also, start small. A pencil sized bit of rocket candy will probably only cost you some fingers if you err badly. My other point of caution to the eager acolyte is nozzles matter more than you think, and not just for thrust. Rockets have a lot of energy, and solid fuels give you no way to control the release of that energy but reaction rate. You don't get valves or gauges, you get to light it and run. Reaction rate increases with pressure and heat. The reaction creates pressure and heat. The chamber and nozzle determine whether it burns like a candle, roars like a rocket engine (the one you want), or runs away and explodes. That balance is delicate. I watched something that was just burning like a candle, but it slowly started to build pressure. It burned like a citronella candle for like 5 minutes. The time between darn, its just a fire and whoops that exploded was a few seconds. As a closing note, the internal geometry of the fuel  and chamber also change the reaction rate significantly, a lot of people add holes of various sizes to increase the surface area, but keep in mind that the geometry changes as the fuel burns away. So, be super careful because it's really hard to predict and failure means explosions, I guess is what I'm saying.