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gatewaycityca
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Making a battery with concentrated lemon juice?
I've been collecting a lot of lemons lately. I wanted to boil lemon juice down to evaporate excess water from it and hopefully have a stronger
concentration of citric acid. Once reason is I wanted to experiment with baking soda and more concentrated lemon juice to get a stronger endothermic
reaction. But now, I've been thinking...I know you can make a small (and very weak) battery from a lemon, and it could power things like a
calculator, LEDs, etc. But what if I use concentrated lemon juice?
If I were to boil down a lot of lemon juice, to get it as concentrated as I can, how much power could I reasonably expect to get? And what would be
the best (though common) metals to use for the electrodes? I'm not expecting a miracle - if I could get a sufficient voltage and current to maybe
power a small DC motor, and maybe a light bulb, that would be plenty.
There are a ton of websites showing how to make batteries from lemons, and of course a lot of kids have done that for school. But I haven't heard or
read about anyone trying it with highly concentrated lemon juice.
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Metacelsus
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Under these conditions, increasing the electrolyte concentration will not appreciably increase the voltage or current. You should do some reading up
on electrochemistry. For starters, a table of standard electrode potentials will help:
http://hyperphysics.phy-astr.gsu.edu/hbase/tables/electpot.h...
Also,
https://en.wikipedia.org/wiki/Nernst_equation
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blogfast25
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@gatewaycityca:
Firstly google for it: it think there are plenty 'instructables' on this subject that will show you which reactions take place. CC is right that the
voltage oobtained from such a battery doesn't vary that much with acid concentration. The lemon juice really acts as an aqueous conductor
(electrolyte) but its conductivity doesn't depend much on citric acid concentration.
Edit: I see Wiki has a good entry on it.
@CC:
'gateway' is a total beginner. Just shoving the electrochemical series and the Nernst Equation under his nose won't significantly help him.
[Edited on 23-2-2014 by blogfast25]
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gatewaycityca
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Thank you for your help, but I'm still confused about why the concentration of citric acid wouldn't affect the output. So it's not the concentration
of the acid, but only the type of acid which determines the output voltage and current capacity of a battery cell? I mean, I knew that obviously a
battery with sulfuric acid or some other strong acid would be much more powerful than one using a weak acid like citric or acetic. But I thought that
a stronger concentration would have a stronger chemical reaction and result in higher voltage. That's why I'm confused.
I kind of understood that table showing electrode potentials, showing which types of electrodes would have a higher potential difference. But I don't
know how to read the formulas! I never studied chemistry in school when I was a kid, and I'm just now learning all this on my own. (Although I could
just Google the formulas to see what materials they refer to).
[Edited on 2-24-2014 by gatewaycityca]
[Edited on 2-24-2014 by gatewaycityca]
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blogfast25
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@gatewaycity:
Start here, especially the part on 'variations'.
http://en.wikipedia.org/wiki/Lemon_battery
Different pairs of metals do significantly affect the voltage but type and strength of electrolyte has little influence.
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gatewaycityca
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Thank you, Blogfast25. I actually looked that up on Wikipedia and I was reading that article. I think I'm starting to understand a little
better now. So what actually generates an electric current in a battery is the reaction between the metals...basically one type of metal trying to
draw ions from the other, with the electrolyte just working as a conductor? I always thought the way a battery worked was from the acid itself
causing a chemical reaction and freeing electrons from the metal somehow as it broke down the metal plates or electrodes.
I have a LOT to learn!
But if the strength or type of electrolyte doesn't have much effect on the voltage, then why do large batteries like car batteries need such strong
and toxic acids like sulfuric acid?
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Artemus Gordon
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Car batteries need to be rechargable, so the anode and cathode reactions need to both be able to run both forward and backward without generating
gases, otherwise you would have to keep replenishing the lost atoms as the gas leaks away. Lead, lead oxide and sulfuric acid is one of the first
combinations that accomplished this, and it works well enough that there hasn't been a big push to replace it. Other rechargable batteries can be
made that use salts instead of acid for the electrolyte such as lithium-ion batteries.
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vmelkon
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Quote: Originally posted by gatewaycityca  | | So what actually generates an electric current in a battery is the reaction between the metals...basically one type of metal trying to draw ions from
the other, .. |
It isn't ions. It is electrons. One of the metals gets oxidized and the other gets reduced. In the case of zinc and copper, zinc gets oxidized
Zn -> Zn2+ + 2 e
and on the copper side, it would be some copper compound on the surface of the metal that gets reduced. Perhaps it is CuO, CuCO3, Cu(OH)2 or some kind
of mixture called patina
Cu2+ + 2 e -> Cu
Signature ==== Is this my youtube page? https://www.youtube.com/watch?v=tA5PYtul5aU
We must attach the electrodes of knowledge to the nipples of ignorance and give a few good jolts.
Yes my evolutionary friends. We are all homos here. |
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papaya
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| Quote: Originally posted by vmelkon | | Quote: Originally posted by gatewaycityca | | So what actually generates an electric current in a battery is the reaction between the metals...basically one type of metal trying to draw ions from
the other, .. |
It isn't ions. It is electrons. One of the metals gets oxidized and the other gets reduced. In the case of zinc and copper, zinc gets oxidized
Zn -> Zn2+ + 2 e
and on the copper side, it would be some copper compound on the surface of the metal that gets reduced. Perhaps it is CuO, CuCO3, Cu(OH)2 or some kind
of mixture called patina
Cu2+ + 2 e -> Cu |
On copper side hydrogen ions are reduced to hydrogen gas, not copper ions (from the same wiki page).
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MrHomeScientist
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| Quote: Originally posted by gatewaycityca | | But if the strength or type of electrolyte doesn't have much effect on the voltage, then why do large batteries like car batteries need such strong
and toxic acids like sulfuric acid? |
Car battery acid is ~30% concentration, so I wouldn't call it strong. I've spilled 20% acid on my hand a few times with no ill effects (washing it off
within a minute or two, of course). I'd also hesitate to call it toxic, except in this case it would be contaminated with lead.
Artemus Gordon's comment is a good explanation.
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Zyklon-A
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Many people (including myself) have spilled ~98% H2SO4 on hands, arms, legs ect. without any chemical burns. Just wash it
off quick enough (within one minute) and if possible dunk affected skin in in a basic solution.
I always keep a big jar full of NH3(aq) mixed with Na2CO3 for washing off acids. And I keep a jar
full of household vinegar, for washing off basic substances.
Also, can we try to remember the definition of ACID STRENGTH?
[EDIT] Typo.
[Edited on 25-2-2014 by Zyklonb]
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gatewaycityca
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Preventing bacteria growth in concentrated lemon juice
Hi guys,
Thanks to everyone who has been helping with my questions lately. So I've been collecting and juicing a lot of lemons lately, and boiling the juice
down to make it very concentrated. At the moment, I've just been storing it in a plastic 2-liter bottle and keeping it in the fridge. I've been
concerned about the juice going "bad" and harboring bacteria. I wouldn't drink the stuff of course, but I'd still be worried about it being
contaminated with bacteria and catching something from inhalation, etc.
My question is, would heavily concentrated lemon juice get so acidic that bacteria couldn't even grow in it anymore? I assume that by boiling the
juice, that would kill anything that happened to be in it. But I'm hoping that I could store the concentration at room temperature and not have to
keep it in the fridge anymore. Would that be safe? I want a container of strong citric acid solution for experiments, not a bacteria magnet. lol
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mnick12
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Boiling alone will not sterilize your juice. You need to autoclave it in a sealed vessel, if you don't have an autoclave a pressure cooker will work.
Also its probably not going to harbor a lot of bacteria, that being said there are plenty of bacteria that can survive and thrive in low pH solutions
(Pediococcus comes to mind). I think molds can tolerate low pH as well, but im not sure.
If you can't sterilize with heat you may consider adding some metabisulfite salt, brewers and winemakers use those to kill spoilage microorganisms
before pitching yeasts.
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ZIGZIGLAR
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You can just place the vial in a water bath in a pressure cooker, as mnick12 alluded to. If you don't have one in your kitchen, you can get "no name"
brand ones from your cheapo stores like Wallmart, I assume.
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papaya
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| Quote: Originally posted by papaya | | Quote: Originally posted by vmelkon | | Quote: Originally posted by gatewaycityca | | So what actually generates an electric current in a battery is the reaction between the metals...basically one type of metal trying to draw ions from
the other, .. |
It isn't ions. It is electrons. One of the metals gets oxidized and the other gets reduced. In the case of zinc and copper, zinc gets oxidized
Zn -> Zn2+ + 2 e
and on the copper side, it would be some copper compound on the surface of the metal that gets reduced. Perhaps it is CuO, CuCO3, Cu(OH)2 or some kind
of mixture called patina
Cu2+ + 2 e -> Cu |
On copper side hydrogen ions are reduced to hydrogen gas, not copper ions (from the same wiki page). |
Now I have question related to my own answer: if the copper side stays "inert", so copper ions don't participate(read that wiki page), then what will
be the potential if I take a battery with the copper electrode paired with even more inert metal like Ag, or graphite? (Cu-Ag and Cu-C). In theory it
must be 0V, is this the case?
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confused
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i would be more concerned about fungi than bacteria, and agree with them that autoclaving is the best option.
However if you cant autoclave it, you could always try using tyndallization although its somewhat of a hassle and not as effective as autoclaving, or
pasturizing it, which isnt as effective as tyndallizstion
http://en.wikipedia.org/wiki/Tyndallization
http://en.wikipedia.org/wiki/Pasteurization
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Tsjerk
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The only thing (except for some very thermophilic archaea) that will survive 100 degrees Celcius are spores, but if you boil twice with 24-48 hours in
between the spores will get the change to germinate and get killed during the second boil.
[Edited on 26-2-2014 by Tsjerk]
[Edited on 26-2-2014 by Tsjerk]
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ZIGZIGLAR
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Well if pasteurization is an option, you can just use your dishwasher on the longest/hottest settings for that. I do that to kill yeast once bottle
carbonation is high enough in sweet ciders so they stay sweet/don't explode.
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Oscilllator
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| Quote: Originally posted by gatewaycityca | Thank you, Blogfast25. I actually looked that up on Wikipedia and I was reading that article. I think I'm starting to understand a little
better now. So what actually generates an electric current in a battery is the reaction between the metals...basically one type of metal trying to
draw ions from the other, with the electrolyte just working as a conductor? I always thought the way a battery worked was from the acid itself
causing a chemical reaction and freeing electrons from the metal somehow as it broke down the metal plates or electrodes.
I have a LOT to learn!
But if the strength or type of electrolyte doesn't have much effect on the voltage, then why do large batteries like car batteries need such strong
and toxic acids like sulfuric acid? |
What nobody seems to have mentioned is that unlike in most batteries, in lead-acid batteries the sulfuric acid does take part in the
reaction, serving as more than just an electrolyte. This is why relatively concentrated sulfuric acid is necessary for a lead-acid battery to work.
IIRC, the reactions are:
Anode: Pb + SO42- -> PbSO4 + 2e-
Cathode: PbO2 + SO42- + 4H+ + 2e- -> PbSO4 + 2H2O
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Tsjerk
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That probably works because your yeast already out-selected every other kind of organism, but is not able to form spores itself.
The problem here is that there are more than likely a lot of spores in the juice, even more than likely also from Aspergillus strains, of which some
have a pH optimum as low as 2!
[Edited on 26-2-2014 by Tsjerk]
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forgottenpassword
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Add some lime juice.
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Tsjerk
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And that would work because?
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bfesser
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Threads Merged
26-2-2014 at 04:50 |
forgottenpassword
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I don't know enough biochemistry to explain how it works, sorry.
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Tsjerk
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Could you tell where you got this information from? There are a lot of antimicrobial compounds in citrus fruits in general (especially the skin), but
they are already in the juice as it is lemon juice to start of with. That is the only reason I could imaging.
Besides that, both bacteria and fungi have a wide range of susceptibility/resistance against different compounds, so the change of finding a microbe
capable of growing on lemon/lime juice in the flask is quite big. I ones saw a fungus growing on 50% ethanol with pretty high copper and azide
concentrations, I believe there is a nice threat about organisms growing in unusual places on this forum somewhere.
Nice example I was just reading: ''Genetic Basis for Daptomycin Resistance in Enterococci (Antimicrob Agents Chemother. Jul 2011).'' Where they manage
to get a susceptible Enterococcus strain daptomycin resistant with a MIC>256 ug/ml, whereas the highest clinical resistance found until publication
was only 8 ug/ml (in just 12 days!).
[Edited on 28-2-2014 by Tsjerk]
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Theoretic
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| Quote: | | I ones saw a fungus growing on 50% ethanol with pretty high copper and azide concentrations |
...
are you even serious
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