PDA

View Full Version : Making citric acid solution for Estes hydrogen fuel rocket



jlcapps
20th March 2010, 06:00 PM
We picked up a previously owned Estes hydrogen fuel rocket at a yard sale and can't find the pre-measured citric acid packets used to make the solution for electrolysis. I understand we can get citric acid crystals from drug stores, but I'd have no idea how to measure, etc.

Does anyone have experience/success w/ this?

Chrisn
20th March 2010, 08:54 PM
Are formulas for this allowed on this forum? Kevin?

Bone Daddy
20th March 2010, 09:56 PM
I have one of these and never got it to work as promised. One of the problems was with the igniter wire not heating up. This was caused by a bad connection where it screws into the base. The whole beep, pull, hold, launch thing never worked. A quick search of the web told me I was not alone in having problems with this $50 or so toy.

The electronics supplied were ridiculously complex. They must have really been worried about getting sued if something went wrong. I ended up taking mine apart and designing my own launch system. There's a switch that turns on the generator and a second switch to fire the igniter. I lost interest in it before I completed it, but did get it to fire at least. (before and after pix)

The citric acid (C6H8O7) is a weak acid and provides the ions needed for their hydrogen generator to work. The packages supplied hold 9 g (0.32 oz). I don't think the concentration is that critical.

Good luck and please post how it turns out.

Gillard
20th March 2010, 10:21 PM
the above post is correct - 9g of citric acid is used.
you can get citric acid in crystal form from most chemists (american drug stores?) and kettle descalers etc are usually citric acid or a similiar weak acid.

as long as you use a weak acid it should be okay, but don't let the acid sit in the chambre for a long time as it will eventually corrode the electrode joints - this happened to mine!

concentration does matter as if the concentration is too low then you will be waiting along time for the hydrogen and oxygen to form.

jlcapps
20th March 2010, 10:25 PM
Thank you all for the good information. We'll more than likely give this a shot tomorrow. I'll let you know how it goes.

Winston
20th March 2010, 10:32 PM
You can buy citric acid at most beer brewer/wine making supply stores. I don't do either, but wanted it as a PC board etchant enhancement, so I had to find a source.

shrox
20th March 2010, 10:57 PM
...you can get citric acid in crystal form from most chemists (american drug stores?)...

Maybe in the vitamin section, or baking section at a grocery store.

We don't have the standard green cross signs out front of pharmacies here. I thought that was cool in Europe.

Winston
21st March 2010, 02:02 AM
Maybe in the vitamin section, or baking section at a grocery store.At least in this large metropolitan area, no major health food, drug store or supermarket chains sell it. Those were the first places I checked. I suspect that any store that carries home canning supplies might carry it, but the sure-fire place to find it will be in a home brewing/wine making supply store.

shrox
21st March 2010, 03:47 AM
What about squeezing some citrus?

Gillard
21st March 2010, 08:49 AM
What about squeezing some citrus?

there's not that much citric acid in orange and lemons, and lot of other stuff that you don't need.
if citric acid is hard to get hold of, then ethanoic acid (vinegar) could be used, don't know how the pKa of the two compare - will check when i get back to my lab on monday.

Gillard
21st March 2010, 08:56 AM
(i found a data book at home)

pKa of ethanoic acid, is 4.75. whereas Citric acid, is 3.13. 4.76. 6.40.

citric acid has three dissociating Hydrogens, that's why it has three pKa values.

so looks as if vinegar could be used, at a push, but it would smell.

jlcapps
21st March 2010, 10:24 PM
The 6 year old remembered that we had some leftover citric acid crystals from what passes for a home chemistry set these days. I measured out ~10g using what has to be the world's crappiest kitchen scale (10g is the extent of its precision) and mixed w/ 8 oz. of water (per the instructions that came with the kit). We got three launches out of it before the batteries gave up the ghost. (The batteries were in it when we bought it last summer, so who knows how old they are.)

I haven't been out in search of a supply for the crystals, but I'm optimistic. One of our local grocery stores has canning supplies, and there's a home brew/winemaking shop not far from where I work.

Thanks again for the help and suggestions.

troj
21st March 2010, 10:33 PM
I haven't been out in search of a supply for the crystals, but I'm optimistic. One of our local grocery stores has canning supplies, and there's a home brew/winemaking shop not far from where I work.

The Internet is your friend; even Amazon sells 'em.

http://www.amazon.com/gp/product/B000J69WFO/ref=pd_lpo_k2_dp_sr_2?pf_rd_p=486539851&pf_rd_s=lpo-top-stripe-1&pf_rd_t=201&pf_rd_i=B00086IE4K&pf_rd_m=ATVPDKIKX0DER&pf_rd_r=08JNJV2KHZPCNZPES0TT

$20 for 4 lbs.

-Kevin

Bone Daddy
22nd March 2010, 03:08 AM
You can definitely uses plain old white vinegar. It too is a weak acid (acetic acid). All you need is a source of hydrogen ions (H+) which are hydrogen atoms that have lost an electron.

For the mildly curious:

It doesn't matter what the source of H+ is, only that there are H+. The hydrogen ions from hydrochloric acid (a strong acid) are identical to the hydrogen ions from citric acid (a weak acid). For our purposes, all a weak acid means is that it is safe to handle. We don't need to worry about how many H+ ions are produced per amount of acid, there is going to be plenty of them for our purposes.

Hydrogen ions can be generated via electrolysis (electricity) from plain old water. It involves breaking the hydrogen bonds that hold the water molecule together. This takes energy. Not very efficient especially at 12 volts. It would take a long time to generate enough hydrogen to make this work.

Adding an acid to water results in the formation of H+ (and a negatively charged anion that depends on the acid used, but makes no difference since all we care about are the H+ ions). What you end up with is a bunch of H+ ions floating around. The water molecules do all the work and an external energy source isn't needed.

So why the battery?

So now you have a bunch of H+ ions floating around which are all revved up with no place to go. Now we turn on our battery. Instead of cleaving water molecules, we are now attracting the H+ ions in the soup to the negative terminal (opposites attract). It's here at the negative terminal that the magic happens.

As the H+ ions are being attracted to the negative terminal, the negative terminal is shedding electrons (electrons have a negative charge). The H+ ion picks up one of these electrons and becomes a hydrogen atom (no charge and no longer attracted to the negative terminal). There is still one more step. Each hydrogen atom being produced bonds with a second hydrogen atom to form hydrogen gas - hence the 2 in H2. This then bubbles out of solution and collects in the assembly the rocket sits on waiting to be ignited. BTW you probably noticed water drops after the hydrogen is ignited. The reaction results in hydrogen reacting with the oxygen in the air forming H2O.

So how much vinegar do you need? You could determine the ration of citric acid to vinegar needed to produce the same number of H+, but that would be too much work.

I'd start with distilled water in the generator and add vinegar and turn it on to see how many bubbles are produced. Repeat until you get a nice stream of hydrogen gas bubbles.

Or just add 9 grams of citric acid crystals and be done with all this nonsense once and for all.

Bone Daddy
22nd March 2010, 04:44 AM
OK, you can just use vinegar straight from the bottle. I have it connected to 12 volts. Lots of bubbles generated. I covered the top with a piece of saran wrap to catch the hydrogen gas.

Yours is the talking one? Mine was the cheap mute one. I'm not sure what it says, but when you start it up it turns on the hydrogen generator. After a preset amount of time it turns off the generator - and arms the ignition switch for a set amount of time. It's controlled by the two relays you see in my previous post. When you pull the cord it makes a connection that allows the button to heat up the ignition wire.

My ignition wire is too corroded to fire it (don't leave the citric acid in the generator for a few months) so I used an alternate ignition source. I also don't have a timing circuit so I just waited a few minutes, applied heat then BANG. Actually big BANG.

Don't know if it is cheaper than using citric acid or not, but it would sure be easier to find.

Let me know if you try it.

Bone Daddy
23rd March 2010, 03:43 AM
I found and read my instructions for the hydrogen rocket. It states their generator does indeed break the H-O-H bonds and generates H2 and O2 gas, which fits the standard model of the electrolysis of water. They state the citric acid crystals "assist in the generation" of hydrogen.

I think they are really downplaying the role of the H+ from the acid.

But hey, I could be wrong............................................. ....

bobkrech
23rd March 2010, 03:42 PM
From a chemist.

All you are doing is electrolyzing water. 2 H2O ==> 2 H2 + O2

Water itself is not a good conductor of electricity so you have to add an ionic material to it to make conduct enough electricity to electrolyze the water rapidly. Citric acid is a weak acid that is consumer safe and not corrosive to the electrodes so this is probably why it was chosen. You can use vinegar, salt, potassium nitrate, ammonium nitrate, or any other ionic material to make the water conductive. Just don't use a strong acid like sulfuric or muriatic acid, or a strong base like lye, or you will destroy the electrodes in the electrolyzer and risk injury if you get it on you.

Once you generate H2 and O2 and heat or spark it, you get an explosion as the 2 H2 + O2 ==> 2 H20 making steam which propels the rocket upward.

Bob

jderimig
23rd March 2010, 10:35 PM
From a chemist.

You can use vinegar, salt, potassium nitrate, ammonium nitrate, or any other ionic material to make the water conductive.

Bob

If you use salt you will get H and Cl I think.

Larry Curcio
23rd March 2010, 11:05 PM
We picked up a previously owned Estes hydrogen fuel rocket at a yard sale and can't find the pre-measured citric acid packets used to make the solution for electrolysis. I understand we can get citric acid crystals from drug stores, but I'd have no idea how to measure, etc.

Does anyone have experience/success w/ this?

You didn't ask, but you can find citric acid in most Indian food stores. (FWIW They are also some of the last common sources of camphor.)

-LarryC

bobkrech
24th March 2010, 12:48 AM
If you use salt you will get H and Cl I think.

Using NaCl certainly would not be a preferred path. What you make will depend on the concentration of the salt, NaCl, and the pH of the solution. Usually if you electrolyze aka line salt water you end up with bleach, NaOCl. This a safe, effective alternative method to kill microorganisms in water and sewerage instead of chlorination. I believe that under certain electrode conditions you can get NaOCl to decompose into oxygen, O2 according to the equation 2 NaOCl ==> O2 + 2 NaCl. Other concentrations and pHs can yield hydrogen chloride, HCl or chllorine, Cl2 as well.

A fairly comprehensive summary of the electrolysis products can be found here. http://en.wikipedia.org/wiki/Electrolysis_of_water (http://en.wikipedia.org/wiki/Electrolysis_of_water)

A "New Age" cure-all industry has grown around the electrolysis of salt water. In various electrochemical cell configurations you can generate hypochlorous acid, HOCl, in one half cell and sodium hydroxide, NaOH, in the other half cell. When you mix the two solutions together you get NaOH + HOCl ==> NaOCl + H2O which is what you make in a cell without the membrane!

http://www.aquatechnology.net/electrolyzed.html

http://boingboing.net/2009/02/23/electrolyzed-water-a.html

Other articles in the wiki reference suggest using sulphuric acid, H2SO4 (battery acid) as the electrolyte. http://www2.uni-siegen.de/~pci/versuche/english/v21-2.html As sulphuric acid is not user friendly, the sodium salt of the acid, sodium sulfate, Na2SO4 can be used as the electrolyte. http://chemmovies.unl.edu/Chemistry/DoChem/DoChem044.html

Sodium sulfate is a very cheap material, and the largest use is as filler in powdered home laundry detergents (http://www.rocketryforum.com/wiki/Detergent), consuming approx. 50% of world production so this might be an attractive source of the material as well.

http://en.wikipedia.org/wiki/Sodium_sulfate

Bob

cls
24th March 2010, 01:28 AM
this is a really great thread!

I've had three of these. the first one never worked.

the second never worked with batteries. I found a 12VDC wall wart and connected it, we'd run it in the front yard on a 100' extension code. after a several hundred launches (probably over 300) the igniter would not glow any more.

the third one would only get about 5 launches on a brand new set of batteries.

we sure had a lot of fun with the wall-wart powered base and all the rockets.

Winston
24th March 2010, 06:39 PM
The Internet is your friend; even Amazon sells 'em.

http://www.amazon.com/gp/product/B000J69WFO/ref=pd_lpo_k2_dp_sr_2?pf_rd_p=486539851&pf_rd_s=lpo-top-stripe-1&pf_rd_t=201&pf_rd_i=B00086IE4K&pf_rd_m=ATVPDKIKX0DER&pf_rd_r=08JNJV2KHZPCNZPES0TT

$20 for 4 lbs.

-Kevin$15.99 for five pounds at a local brewing store. One pound for $4.99. No shipping, no wait. Another store wanted more for the same amount, so it pays to shop around (by phone) if you have multiple local options.