Chemical Forums
Specialty Chemistry Forums => Citizen Chemist => Topic started by: EDsteve on April 24, 2020, 07:31:10 AM
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Hello dear forum,
to be honest i am a electronic guy and my chemical skills aren't even enough to know in which sub forum my question should be in.
I am not sure for what to google. So maybe my question is answered already a 1000 times. Please be nice to me :D
Problem:
I am building a floating peer from empty water bottles. But as deeper the bottles go into the water as more compressed they get and loose buoyancy. Also waves will compress them in time as well nobody wants to hear the crackle sound when they deform all the time.
Solution:
Put pressure inside the bottles. I thought about several methods already:
1. before closing the bottles, put them in ice cold water for a few seconds. Result: works great, but i prefer to have higher pressure inside.
2. Put a small portion dry ice inside. Result: Would be perfect i guess. But I live on Sumatra in the jungle. Dry ice is way to far away.
3. Let a small fire cracker explode inside after the cap is closed. -> Still looking for firecrackers to try it. Sounds funny. But can work right?
Now i started thinking about baking soda and vinegar or any other house hold ingredient. Fermentation? But my knowledge is almost zero about these things. There will be thousands of bottles. So it should not be too expensive. And of course efficient. So a small amount should lead to a big volume of gas.
I should get most common chemicals cheap online. Sooo. Give me something to try and i will do :)
Regards
ED
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I am seeing visions of exploding or imploding bottles.
Scary to me.
Setting aside how workable this idea is.
What is the stress level of these bottles and how are you going to be sure you do not exceed it.
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I will start small and add more if pressure not enough. So i can be almost be certain not to exceed the limit. When pressure high enough i know the right amount of the "ingredient" to put inside and the mass production can begin :)
And of course testing must be done behind a wall.
A soda bottle can hold minimum 150PSI or 10 Bar. There are many youtube videos out there who demonstrate that. I just made a quick test and jumped a few times on one of the bottles i have (not Soda). But they seems strong enough too. No crack.
Two Bar should be enough for my project.
Any idea?
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What is the stress level of these bottles and how are you going to be sure you do not exceed it.
Carbonated drinks go up to 50 psi, quite a pressure.
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Yes. They do. Coca Cola bottles for example are tested to withstand 150 PSI. And the stronger ones even 250PSI.
Is my question so difficult?
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Just now thinking about it and also wanting to make it safe and ease to do.
These come to mind
Baking Soda and Vinegar Chemical Reaction
https://www.youtube.com/watch?v=nRMyMIy7U6E (https://www.youtube.com/watch?v=nRMyMIy7U6E)
The classic elephant's toothpaste
http://www.periodicvideos.com/videos/elephants_toothpaste.htm (http://www.periodicvideos.com/videos/elephants_toothpaste.htm)
without the soap and color
This was from a quick search on GOOGLE
What do you think
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Yeah. I tried the baking soda some days ago. But the volume expansion is way to small. I have a few thousand bottles here. So i can't use 200ml vinnegar and 2 big spoons of baking soda for each :D
The ingredients for elephant toothpaste are pretty high. But i still have the feeling that the mini firecracker solution could work better, easier and much cheaper. Or are my feelings in the wrong direction?
After some more tinkering... the materials used in smoke bombs can do the trick. But maybe too hot for too long time.
I understand that a expanding volume in a closed space can be dangerous. So i can see why you want to be on the safe side with your information. The more efficient solutions are not for kids any more i guess... But i just thought i ask here before i go to the anarchists forum. Joking :)
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A pump for bicycle tyres would be best, but I don't see how to seal the many bottles.
Natural yeast and something to feed it. I fear the rests will rot.
Yes, bicarbonate or some carbonate and some acid like vinegar. More concentrated acid would leave less water, so the bottle lifts more weight.
Firecrackers are not my first choice. The corrosive gas, especially SO2, may harm the plastic bottle over time.
Please protect your ears. Once with friends, we let soda bottles explode by pouring liquid nitrogen in and closing. My friend stayed deaf for half a day as he went too close. How much luck he had with shrapnel, I don't know.
Use scales to measure the amount of baking soda and acid so the pressure is reproducible. Cheap on eBay or Alibaba. Pour a clear excess bicarbonate to leave no acid damaging the plastic. You can prepare many doses in advance.
Did you check how durable the bottles are under sunlight? A protection by the pier can be useful.
Let a pier-review check your design.
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Hello Enthalpy,
and thank you for your answer.
Natural yeast and something to feed it. I fear the rests will rot.
Last night i put 1g dry yeast and a bit sugar water (2cl) in one bottle . The result looks promising. Can you explain your "fear" about the rotting situation?
As already mentioned i tried the baking soda and vinegar(25%). But the pressure is way to small compare to the amount i have to put in each bottle.
Did you check how durable the bottles are under sunlight? A protection by the pier can be useful.
Yes. I already built a hot water solar heater from empty bottles and they do last quite a while (more than 5 years in direct sunlight). But with the peer they will be covered from all sides. So that should be fine for a long time.
Let a pier-review check your design.
I am still not exactly sure what it will become. Peer, floating platform, catamaran style boat or even an island. I will start small scale first and built two pontoons with 4m lenght and 60cm diameter. After collecting some experience how it behaves i will decide in which direction i go from there.
As you can see in the attachment. I am still in the beginning phase :)
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I put 1g dry yeast and a bit sugar water (2cl) in one bottle. Can you explain your "fear" about rotting?
If you leave organic materials in a bottle for years, bacteria transform it into stinking and badly looking compounds. An exception would be if voluntarily introduced bacteria, for instance yeast, produce enough alcohol to kill all bacteria in the bottle. That's why you can keep wine for years (it will turn to vinegar but keeps safe for drinking).
I didn't check how much water is needed. While producing CO2, alcohol is made too, and some 14% alcohol stop the fermentation as the bacteria die.
I tried baking soda and vinegar(25%). But the pressure is way too small.
Vinegar is a very dilute acid, you need too much of it. Take a more concentrated acid, but please be careful. Prepare some means (the Ocean) to rinse yourself immediately. Wear protective goggles.
I prefer much the less strong polyacids like citric acid, tartaric acid
https://en.wikipedia.org/wiki/Citric_acid
https://en.wikipedia.org/wiki/Tartaric_acid
More protons hence gas per kilogram, less dangerous.
Oxalic acid is more caustic
https://en.wikipedia.org/wiki/Oxalic_acid
Battery acid (=sulphuric acid) is cheap and available but dangerous, and you need more or it for the same gas amount. Try to avoid it.
Can you compute the amounts? Introduce an excess of baking soda, as it shouldn't damage the plastic over time.
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@EDsteve
Your bottles look like plastic water bottles and not plastic soda bottles.
I now notice you said that in your original post.
I thought that not all water bottles had the same pressure requirements as bottles with carbonated drinks.
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A side note
Different varieties of yeast tolerate different levels of ethanol.
I expect the best are pricey.
It seems to me most any yeast will keep most bacteria count down.
I am betting that enough carbon dioxide would be created before death due to ethanol level.
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@billnotgatez
You are right. I don't use soda bottles. Water bottles are just more common here. But also these bottles are stronger then we might think. A full bottle falling from 10m. No harm. I was jumping on a bottle. No harm. So i am pretty sure they can handle much more than 1 bar easily.
@Enthalpy
Thank you. Your post really helps me a lot. Citric acid and Oxalic acid is very cheap (1,3USD per KG). And if i understand you correctly. Oxalic acid is more efficient for my case but also more dangerous. Correct?
Can you compute the amounts?
My skills in chemistry are pretty low. So i would just start small and do some try and error. But if you have a rough idea. I would start with that first :)
I also started a course on https://www.khanacademy.org to gain more knowledge.
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I expect the best [varieties of yeast] are pricey.
Grow the yeast
Anyway, I prefer the bicarbonate and citric or tartaric acid method.
I am betting that enough carbon dioxide would be created before death due to ethanol level.
It's a matter of water and feed amount compared with the bottle's volume.
Your bottles look like plastic water bottles and not plastic soda bottles. [Not] the same pressure requirements.
Well done! Inadequate for 1+1atm.
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Oxalic acid is more efficient for my case but also more dangerous. Correct?
Oxalic acid saves a little mass but is much more caustic to your skin and eyes. Citric or tartaric acids are much safer. As you find them, prefer these, absolute clear choice.
Wear a scuba diving mask to protect your eyes.
My skills in chemistry are pretty low. So i would just start small and do some try and error. But if you have a rough idea. I would start with that first :)
Many people here can help you compute the amounts. Normally on this forum, we shouldn't give you the ready-to-use answer.
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Can you compute how many moles of CO2 are needed to bring 1L bottle volume from 1atm to 2atm, once the temperature settles to the Ocean's temperature?
https://en.wikipedia.org/wiki/Ideal_gas_law
Then, 1 mol of bicarbonate releases 1mol of CO2. I believe it also takes 0.5 mol of citric acid. Can someone confirm this please? pKa 3.13, 4.76 and 6.39.
Maybe you can check Wiki's pages
https://en.wikipedia.org/wiki/Sodium_bicarbonate
https://en.wikipedia.org/wiki/Citric_acid
(and tartaric acid if you can buy some. It should need less mass than citric acid)
and find the mass for one mole of each.
Then you can deduce the mass of acid for the bottle's volume, and a minimum mass of bicarbonate. I'd put some little excess of bicarbonate, less harmful to the plastic than excess acid.
A water amount must still be estimated.
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pKa2 of carbonic acid - 10.3
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It's all new territory for me. But i will give it a try:
This website told me the Volume of 1 mole of CO2 at room temp and pressure:
https://sciencing.com/calculate-volume-co2-7868589.html
So 1 mole CO2 needs a volume of 24 liter at room temperature.
This website lets me calculate the density of moles in relation of pressure:
https://socratic.org/chemistry/the-behavior-of-gases/molar-volume-of-a-gas-224-l-at-stp
So i took the formula in the attachment and changed temperature to 300K (lake temperature) and the pressure to 2 atm.
So that means for my understanding: 1 mole CO2 has a Volume of 12,3 Liter at 300K and 2 atm pressure.
So if i have a 1,5l bottle: 1,5 / 12,3 = 0.122
That means i need 0.122 moles of CO2 to create a pressure of 2 atm in a 1,5l bottle.
And this nice online converter converts mole to gram:
https://planetcalc.com/6777/
So according to my (for sure wrong) calculation i need 2,2g baking powder and 12g citric acid. Does that sound right to you?
The amount of water needed depends on the solubility of the two "ingredients" right?
Sodium bicarbonate: 100 g/L (at 25degrees) -> I need 22ml water to dissolve 2,2g baking powder
Citric Acid: 64.3% w/w (at 25degrees) -> I need 20ml to dissolve 12g Citric Acid
So would 22ml do the job? Or do i have to add 20ml plus 22ml?
Thanks for all your help. I really appreciate it.
P.S.: Tartaric acid is ten times the price. But if the needed amount is a lot less. Then worth it. Because it also needs a lot less water to dissolve too.
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That means i need 0.122 moles of CO2 to create a pressure of 2 atm in a 1,5l bottle.
Yes.
So according to my (for sure wrong) calculation i need 2,2g baking powder and 12g citric acid. Does that sound right to you?
Unfortunately you are right - this is wrong. Hard to say why. You need more sodium bicarbonate but less citric acid (although using some excess is a good idea.
Trick is, baking powder is not pure bicarbonate, so you will probably need more.
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Okay. Cool. That already gives me some numbers i can start with. Of course i will start with half of that. Just to see what happens and then go from there.
Another question i am not sure about:
Sodium bicarbonate is baking soda and not baking powder. So i should use baking soda instead of baking powder?
Correct me if i am wrong :)
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Sodium bicarbonate is baking soda and not baking powder. So i should use baking soda instead of baking powder?
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Correct
According to WIKI baking powder can be baking soda with added ingredients.
You want the plain baking soda.
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This is how I imagine the process:
- Bottle is full of air at 1 atm
- Bicarbonate and acid are poured in, in proper amount
- Stopper is closed, pressure rises to 2atm
So CO2 must provide only 1atm in 1.5L, or equivalently, only 0.75L at 2atm, as air provides the rest for free. That is, only 0.06mol CO2 are necessary.
Exegesis by AWK-logists suggests that 1 mol citric acid frees 3 mol CO2, not 2, because citric acid acts by all its three functions. Less citric acid needed. Hope I grasped it properly, I never needed such a thing for rocket engines.
One 150g mole of tartaric acid frees 2 moles of CO2. One 192g mole of anhydrous citric acid frees 3 moles of CO2.
Amount of water: if the acid and the bicarbonate are first dissolved separately, then the solutions poured in the bottle, solubilities apply. A bit excess water helps dissolve.
The presently estimated water amount has no big drawback, does it? It only reduces the buoyancy of the bottle. I suppose it can be seawater, just try.
Alternately, fine powders of bicarbonate and acid could be mixed dry, introduced in the bottle, and water be added. This might accept less water, or not, difficult to predict. I don't see clear advantages to this. Maybe the reaction is slower, giving time to close the stopper and get away, useful.
Please take some precautions before the first trial and during the production. While a soda bottle is not a grenade, I know by experience it makes a strong bang, and among thousand bottles, some will explode. Do it outdoors. Protect your ears. Maybe a scuba mask protects your eyes against debris, and skiing gloves protect your hands, but maybe not, I don't know. I would leave the bottles behind a wall or sandbags immediately after closing the stopper. Use a mirror on a boom to watch if bubbling is finished.
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Thanks for your infos.
Yesterday Citric acid and baking soda arrived so i had the chance to play around a bit.
I have done only tests with 5 different mixtures for now. And for now i get pretty good results with 7g citric and 7g baking soda plus 15ml water.
The trick is to keep the bottle almost horizontal at around 15 degrees. Water first which runs to the bottom and then the powder mix with a narrow spoon which stays on the upper half. So the water and the powder does not mix right away-> Close the lid and then give it a quick shake.
Otherwise i will loose most of the pressure because the reaction happens pretty quickly.
Unfortunately these caps from the not-soda-bottles are very sensitive. The threshold between overturn and a tight seal is very small. So i had some difficulties with that... leaks etc... But a total pressure of 1,5atm should actually do it.
Will do more testing tomorrow again with my full face snorkeling mask :)
I will post my final results here when i am satisfied.
The presently estimated water amount has no big drawback, does it? It only reduces the buoyancy of the bottle. I suppose it can be seawater, just try.
Yes. Correct. So if i need 15ml for each bottle. That means i will loose around 1% buoyancy which is totally worth it because i will gain maybe 30% buoyancy because of the internal pressure.
BTW: i live at a lake :)
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Please protect also your hands and arms. Just a water bottle isn't so horrible, but you don't need to hurt yourself.
Nice idea, introducing separately the powder and the water. Better than pouring the water just before shutting the bottle. But over 1000 bottles, you will definitely make mistakes.
[...] I will gain maybe 30% buoyancy because of the internal pressure. [...]
As a child, I wanted to pump pressurized air into boats so they could carry more load. No adult around me could correct that.
As opposed, a vacuum aerostat is vaguely suggested there
http://www.physicsforums.com/showthread.php?t=524229
http://www.physicsforums.com/showthread.php?p=4121567#post4121567
http://www.physicsforums.com/showthread.php?t=647031
pretty much useless, an endeavour for good mechanical designers. Not because it's easy, but because it's difficult.
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Yes. I use gloves and snorkeling mask. But it's kind of difficult to make a bottle explode. Of course i also tried it out of curiosity and failed. The cap of the non-soda bottles will release pressure before anything happens. And the soda bottles. They need 10 times of the mix. So i think that project is pretty safe.
Another question: The transparent liquid which is the end result in the bottles. Is that still harmful?
As a child, I wanted to pump pressurized air into boats so they could carry more load. No adult around me could correct that.
As mentioned in my first post. I am adding the pressure to protect the bottles from getting squeezed under water. So if they keep their volume instead of getting squeezed. That's my 30% increase of buoyancy. :)
I am well aware that volume (displacement) is the key of buoyancy and not what is inside. Well... not really accurate because if steel would be inside. It will sink :) And adding air would actually make it more heavy too = worse :D
I still like the vacuum balloon idea from the links :D
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The transparent liquid which is the end result in the bottles. Is that still harmful?
Not more than the bicarbonate nor citric acid themselves (actually even a bit less) - I would not bath in them nor eat/drink them, but other than being possibly a mild irritants they are all reasonably safe.
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[...] it's kind of difficult to make a bottle explode. Of course i also tried it out of curiosity [...]
Somehow I had guessed you would. ;D
It wouldn't hurt to recompute cleanly the amounts of bicarbonate and acid, in order to save them and to limit the produced pressure. There was a bug in the 1+1atm computation.
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I totally love this experiment, EDsteve.:-) How did it go? Did you manage to pressurize some significant number of the bottles to actually build something?
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Hey Ren,
yap. The idea sounds great :)
But it should be also worth it. And according to my calculations i can't do it with acid and baking powder because the shipping costs here in Indonesia will make it too expensive.
I pressurized around 80 bottles already but i am thinking to use fermentation in future. Yeast can basically be made for free. So only sugar is needed which i can find at the next shop. It will also be easier and faster to add the indigence in the bottles because the process is very slow.
But i have the problem to start too many projects at the same time. So the progress is sloooow ::)
I will keep this thread updated if there is an update :)
P.S.: Not-Soda-bottles can still hold a good amount of pressure but maybe 5-10% don't. That's another lesson i learned.
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For the same ΔP*V, the shipped mass is smaller with dry ice (it's CO2). You can conserve it for weeks in polystyrene foam. Find something (with paper?) that gives you time to close the bottle before contact with the walls evaporates the ice.
Liquid nitrogen would be even lighter. Maybe it's less available than dry ice. More difficult to introduce in the bottle with delayed evaporation. Aluminium foil maybe.
If you live in a remote location without dry ice nor electricity, make your earning of delivering dry ice for fridges.
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Champagne shall be your model for pressure fermentation. I dislike the time it takes, the risk of rotting, the doubtful reproducibility.
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Air is the cheapest and most available gas. I suppose a reliable valve (not for bike tyre) per bottle is too expensive.
The only way I see to use the original caps that fit the bottles is to operate at depth in the lake. 5m for 0.5bar overpressure, this is difficult in apnoea, feasible with oxygen.
Many processes become possible then. With diving bottles, expire your air in the bottles, close them. Or pump air from the surface through a pipe. Or bring air to the depth in more bottles, fill some while emptying others.
The bottles should be ballasted. I'd sink and raise them with ropes. A funnel helps transfer the air.
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After some time an update with no good news.
Turns out that these aqua bottles can hold the pressure only for a few weeks. Mostly the cap splits. Only 2 out of 50 bottles are still under pressure. I am sure coca cola bottles can do what i need. But too hard to get. So i am not continuing this idea.
Thanks again for all the helpful input.