Sciencemadness Discussion Board

MgSO4 --> H2SO4

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Saerynide - 11-4-2004 at 04:58

The electrodes dont corrode too much if the cells are separated by a salt bridge, but then voltage drops by so much :mad: I still need to get myself a multimeter to measure the voltage and current in my cell.

darkflame89 - 11-4-2004 at 05:29

Organikum, what do you mean by "not too happy with the H2SO4 part"? Aluminium sulphate hydrolyses all right right, the trouble is keeping the result away from each other, that is prevent the aluminium hydroxide from reacting with H2SO4 again.


I tried the electrolysis of my produced CuSO4 again with pencil electrodes sharpened on both ends. The electrodes corroded away preetty fast. Carbon powder was all over the solution in the end. And, at first the cathode side bubbled away with what i think is H2 gas. Cu(OH)2 also collected around the electrodes. I think the CuSO4 concentration is too low. When i added more CuSO4 powders, the bubbling at the cathode side was reduced, and copper started to form. The anode side corroded the fastest. The electricity stopped in 2 hours as the sharpened end of the pencil had disappeared into the solution. Also, i will be away on a camp for the next 3 days, therefore i had to stop this experiment.

The pH however at this point of time is 4.

Organikum - 11-4-2004 at 05:51

In my part of the world neither aluminium sulfate nor aluminium chloride nor ferric chloride hydrolyses easily to form the correspondending acids. In the best scenario with heaps of water there will be some equilibrium building up, but by no way a complete decomposition of the sulfate/chloride will take place. (not speaking of decomposition of the chlorides by heating - is understood).
Making aluminium sulfate is useless - there is no sense in this. Btw. why doesnt MgSO4 hydrolyse if Al-sulfate does?

Sorry to take your idea down. Making iron or copper sulfate and using this might be a good idea, but just changing the electrolyte when it gets basic as I told before is a better idea.

Electrode material.

axehandle - 11-4-2004 at 10:04

Quote:

The process is taking too long to produce a small quantity of acid. The carbon electrodes, which are correded at high voltages must be replaced, but with what?! If the carbon rods could be replaced by some other inert material (which is not gold and neither platinum ) the process could be scaled up by increasing the voltage right? Does anyone have any suggestions.


Why? Why not use gold or platinum? A flattened thin wire won't cost as much as you might imagine, and it will conduct far better than graphite. I'd go with Pt as it's higher on the "inertness scale" than Au, but it's also twice as expensive.

Example: Take a 0.5mm thick Pt wire, 100mm long (to make 2 electrodes).
The volume of the metal is pi*(0.25*0.25)*100 cubic mm. This equals about 0.01963 cubic centimeters. The density of Pt is about 21, so the wire will weigh about 0.41g. Such a wire would cost about 230SEK, equaling about 20 Euro. Not so horrible, no?

Have anyone BTW thought about using Ag? Would it be inert?

[Edited on 2004-4-11 by axehandle]

Esplosivo - 11-4-2004 at 14:02

Thanks axehandle. I've just checked and the minimun I can buy of Pt wire of a thickness of 0.46mm is 15 cms. I'll try to buy the wire soon, though exams are getting near. This time will help me increase my budget :P thanks for the help

a little warning

axehandle - 11-4-2004 at 18:02

No worry, just make sure you don't accidentally use AC during the electrolysis if there is hydrocloric acid present in the fluid -- the Pt will dissolve, forming hexacloroplatinic acid, which would be a very expensive way to ruin your day..... :o

Edit: Also, if you get jewelry grade Pt, it's normally alloyed with 5 to 10 % Pd to make the Pt harder. That shouldn't matter though.


[Edited on 2004-4-12 by axehandle]

Organikum - 12-4-2004 at 02:29

Another example:
(from Ullmanns)
Zinc electrolysis:
- Cathode: Al
- Anode: Pb/Ag (plain lead will work)

I suggest the use of an lead anode in the MgSO4 electrolysis as the anodic part will be similar to the zinc-sulfate process. As long the concentration of the MgSO4 doesnt drop to low a decomposition of the lead electrode will be no problem.

What I see being a problem here in the described experiments is that you all run your cells much too long without refilling electrolyte - this makes your electrodes decompose. Use bigger cells or refill! Change the electrolyte in the cathode chamber and refill MgSO4 in the anode chamber from time to time.
You really dont need Pt electrodes here.

:)

[Edited on 12-4-2004 by Organikum]

Saerynide - 12-4-2004 at 03:02

But if you change the electrolytes, wont you be having salt in the acid? Can that be crystalized out by fractional crystalization? And, how do you know when to change the solutions?

Organikum - 12-4-2004 at 03:57

When the ph in the cathode chamber gets low you might change the electrolyte in there and - refill MgSO4 in the anode chamber. I dont think you can "overfill" the electrolyte in the anode chamber, so just fill in MgSO4 until it doesnt dissolve anymore. A graphite alectrode can be used as anode - keeping temperatures below 50°C or less will help to protect it from decomposition. I dont know about the solubility of MgSO4 in concentrated H2SO4 but I GUESS it will precipitate upon concentrating the sulfuric acid by boiling away the water.

:)

Saerynide - 12-4-2004 at 05:42

The pH in the *cathode* gets *low*?? :o Doesnt the pH at the cathode get high and becomes more basic?

Organikum - 12-4-2004 at 06:12

Yes ph gets high - more basic - my bad sorry. :o

Saerynide - 12-4-2004 at 06:22

Lol no prob. You had me scratching my head there for a while :D

If I understand correctly what you're saying, I should do this:

Change the catholyte where the Mg(OH)2 is.

Add more MgSO4 to the anolyte where the H2SO4 is.

Is that right?

Man, I better buy some huge jars to store the spent catholyte so I can recycle whatever I can crystalize out :D

Edit: typos :P

[Edited on 12-4-2004 by Saerynide]

mea culpa

axehandle - 12-4-2004 at 06:32

Well, *hhrrrrm* *blushing*, yes, Pb is slightly less expensive than Pt..... although Pt has many other.... interesting.... applications.

KClO4, HNO3, H2SO4......

Edit: Btw, if I'm lucky I will have 4.5g of Pt tomorrow! Oh, yesssss, precioussssss........

[Edited on 2004-4-12 by axehandle]

Saerynide - 12-4-2004 at 06:54

Doesnt Pb turn to lead sulfate like in lead acid batteries? :o

Edit: Nice new title btw :D If I get this working, do I get a special title? *sniff* :(

[Edited on 12-4-2004 by Saerynide]

axehandle - 12-4-2004 at 07:02

Quote:

Doesnt Pb turn to lead sulfate like in lead acid batteries?

Not according to Organikum, and he always knows what he's talking about. See a few posts above. Besides, if it did, it could probably be filtered out easily --- and lead is cheap. I'd still go for Pt though.... or iridium... :)
Quote:

Edit: Nice new title btw If I get this working, do I get a special title? *sniff*

I'd suggest brown-nosing a moderator. That's what I did. :)

[Edited on 2004-4-12 by axehandle]

Organikum - 12-4-2004 at 07:48

As seen I dont always know what I talk about - ph low and high, auwei.....

But as I took the Pb anode plain from the Ullmanns it should be right to the point. ;)

Maybe it is worth a try just to refill MgSO4 in both chambers - anode and cathode - the Mg(OH)2 should precipitate for being not soluble in water if "Kings Chemical Survival Guide" is right. (I will look it up in the Merck later).

Anyways - replentishing the electrolyte is a logical MUST - it wont last forever. The possible concentration of H2SO4 should be quite high - 30%+ perhaps even 50% or more. At least this are the concentrations electrolytic zinc is made with - 30% starting and not higher as 50% if I remember right. Lead anodes are used so this will be no problem.

:cool:

Esplosivo - 12-4-2004 at 10:45

Organikum, lead reacts with sulphuric acid forming lead (II) sulpahte right? This lead (II) sulphate is insoluble (especially in the sulphuric acid because of the common ion effect) and will therefore form a coating on the lead electrode. Now, ionic salts do conduct electricity, but in solution or in the molten state, NOT in the solid state. How will the lead electrodes conduct electricity with a surface coating of lead (II) sulphate?!

axehandle - 12-4-2004 at 11:22

I have a wild speculation: I suspect that the lead sulfate won't adhere to the lead anode, but sink to the bottom of the vessel due to the huge density of lead. This is just an uneducated guess.

I'd still go with iridium-clad platinum..... :)

Esplosivo - 12-4-2004 at 13:23

I doubt that lead (II) sulphate would fall of the electrode. When reacting Pb with sulphuric acid a 'protective' coating of PbSO4 forms, after which no more reaction occurs since the inner Pb is not in contact with H2SO4. But it might be different in the case of electrolysis, I don't know.

[Edited on 12-4-2004 by Esplosivo]

Organikum - 13-4-2004 at 00:41

Lead is quite resistant to H2SO4 - thats why it was widely used in the production of the acid - look for "lead-chamber" or ask axehandle. On the second side there is the prsence of the MgSO4 protecting the lead electrode - this will predominantly get decomposed - as told as long the temperature is not to high and the concentration of the MgSO4 not too low the lead wont get attacked. (better: it will get attacked only a little bit ;))

Ok, ok:
The Merck says lead reacts with HOT CONCENTRATED nitric, sulfuric and hydrochloric acid.
So it wont react with sulfuric acid if it is not to hot and too concentrated - as told 50°C and 50% will cause no problems - higher temps/conc. probably will.
Formed lead-sulfate will dissolve in diluted H2SO4 but will precipitate upon concentrating the acid. It wont hurt anyways - I suppose nobody is going to drink the selfmade H2SO4? ;)

So we have two reactions to consider:
- the usual H2SO4 + Pb = lead-sulfate:
This takes not place at the named temperatures and concentrations
- the electrolytic decomposition of lead to form lead-sulfate like it car batteries:
This takes not place as long enough MgSO4 is present, as the electric energy is used up in the decomposition of the MgSO4. Only if your MgSO4 concentration would get to low you would start to decompose your electrode.



[Edited on 13-4-2004 by Organikum]

Esplosivo - 13-4-2004 at 01:44

Thanks a lot for the explanation Organikum. I guess I will try the electrolysis using lead plates obtained from car battries then.

Saerynide - 13-4-2004 at 01:46

Hm... now where to get lead :S

ALL CAPS

Organikum - 13-4-2004 at 01:51

CARBON CARBON CARBON CARBO CARBON

btw. did I mention carbon rods?
The same as for lead: As long concentration of the H2SO4 is not to high and the concentration of the MgSO4 not to low this will work fine. Even stainless steel might be worth a try.
Just replentish your electrolyte!

ALL CAPS

Organikum - 13-4-2004 at 01:53

CARBON CARBON CARBON CARBO CARBON

btw. did I mention carbon rods?
The same as for lead: As long concentration of the H2SO4 is not to high and the concentration of the MgSO4 not to low this should work fine. Even stainless steel might be worth a try.
Just replentish your electrolyte!

Saerynide - 13-4-2004 at 02:46

I was using carbon rods before :P

Organikum - 13-4-2004 at 04:34

Ok, then try some stainless steel or nickel if you cant get hold of lead.

Lead:
- (shotgun) ammunition
- fishing weights
......

Esplosivo - 13-4-2004 at 05:33

As I already mentioned, Lead plates can be found in car battries. I'll get one used. One battry will provide you with more than enough lead plates if you can obtain one.

Saerynide - 13-4-2004 at 05:42

Its not easy for a 17 yr old girl living in a country where practically everything is regulated to get their hands on a car battery :( I do have a sealed lead acid battery at home, but I dont wanna dismember it :(

Organikum - 13-4-2004 at 06:51

We work hard on finding workarounds regarding you being underaged and living in a restrictive country, but there is no hope I fear for finding a workaround for you being a girl... ;)

lead

axehandle - 13-4-2004 at 06:57

Go to a scrapyard and buy used x-ray shielding. It's almost for free.

Or buy air-gun pellets. They're lead (although probably alloyed with tin and / or antimony).

Hell, I've got tons of pure lead here. If all else fails I could send you some. I'll even cast two staffs for you if you like.

chemoleo - 13-4-2004 at 07:09

you can also get lead from builders supplies, in this country they use it a lot for roofs, water drainages, etc etc.
I can't believe you'd have a problem getting some lead, with all the ideas above!!

Saerynide - 13-4-2004 at 07:43

This sounds crazy (and it IS!!), but air rifles are illegal here, building suppliers here dont sell to individuals (or single pieces/small quantities) and the scrap yard is off shore on some remote island :o

Maybe I will get lucky and find another lead acid battery in the school dumpster or last resort, I *could* dismember mine and risk being hosed with acid, but I dont wanna part with it nor do I want to lose any skin! :(

Edit: Axehandle, I really appreciate you sending me some, but the shipping would be almost insane :(

[Edited on 13-4-2004 by Saerynide]

Eliteforum - 13-4-2004 at 08:31

Last time I took apart a SLAB (Sealed Lead Acid Battery) It didn't have any acid in it to splash about.

Just damn(ish) cloth like material inbetween little strips of lead.

Organikum - 13-4-2004 at 09:13

And what about fishing weights?

axehandle - 13-4-2004 at 10:01

The shipping to Singapore from Sweden of an envelope weighing a maximum of 100g costs only about 2.5 Euro.

For one weighing a maximum of 250g, it's about 5 Euro.

Time to delivery: 3..4 days.

Make up your desired dimensions of the electrodes, and I'll cast them. With an embedded copper wire partly coated with PVC, if you'd like.

Organikum - 13-4-2004 at 10:11

!!!
Quote:

With an embedded copper wire partly coated with PVC

me too! me too!
:o:o

Organikum.....

axehandle - 13-4-2004 at 10:14

..... I strongly suspect that lead is much more available to you than to Saerynide...... cast your own electrodes.... :P

Organikum - 13-4-2004 at 10:47

Bäh!

I would have offered you some feathers from vulture´s wings, Ignorantly_Intelligent´s soul AND one testicle of, eh how was the name of this mad swede here again.....?

But ok.
As you like it.
:mad:

Hermes_Trismegistus - 13-4-2004 at 14:10

Quote:
Originally posted by Saerynide
Its not easy for a 17 yr old girl living in a country where practically everything is regulated to get their hands on a car battery :(


You're a girl!?!

You can't get a car battery....?

You can't get roof/chimney flashing?

You're a girl :o

darkflame89 - 14-4-2004 at 01:25

Garrh...Back from the stupid camping trip, reading the long replies by everyone.

So, Organikum suggested lead and gold electrodes. I thought too that gold electrodes are not bad. (I could use some gold necklace as electrodes). But only gold jewellery are available. But i will look around for thin gold wires.

Lead, hmmm, it is tricky... Lead is reaaallly uncommon here, never seen lead in my 15 years of lives.I could appreciate that if some short lead bars could be sent here.

And, Organikum what do you mean that aluminium sulphate does not hydrolyse too well. All you need to do is to give the solution gentle agitation to precipitate. Ok, i agree that the formation of a base and acid in the same container does not bode well, i am still thinking this through...:(

Organikum - 14-4-2004 at 01:33

I NEVER suggested GOLD electrodes, damn.

And the problem with the aluminium sulfate is as I wrote it: EQUILIBRIUM. You cannot hydrolyse the sulfate to get any serious amount of H2SO4. This is not practical.

darkflame89 - 14-4-2004 at 01:39

:(Sob, i was just trying to think of other possible ways to make H2SO4 other than graphite electrodes...

Edit: About the gold electrodes, sorry, that was axehandle's suggestion

[Edited on 14-4-2004 by darkflame89]

Saerynide - 14-4-2004 at 01:58

Quote:
Originally posted by Organikum
Bäh!

I would have offered you some feathers from vulture´s wings, Ignorantly_Intelligent´s soul AND one testicle of, eh how was the name of this mad swede here again.....?


ROFL. Feathers and souls are nice... but.. a .... urm... testicle?? :P
Quote:
Originally posted by Hermes_Trismegistus
You're a girl!?!

You can't get a car battery....?

You can't get roof/chimney flashing?

You're a girl :o


Lol. Yeah, I am :D I always found people's reaction after realizing Im not a guy very amusing :D

Electrodes, schmelectrodes....

axehandle - 14-4-2004 at 06:22

Look what little me bought today....... the plates are 1mm Ti plate, the wire 0.8mm x 300mm pure Pt, and the mesh is a <b>Platinum Clad Titanium Anode!!!!!!</b>

I accidentally found it while waiting at the counter, flipping through their catalogue.... and it only cost about 50 Euro!!!!!!

And..... they have Graphite Rods too!!!

I think I'm getting a spontaneous orgasm!!!

Saerynide - 14-4-2004 at 07:26

Wow. The platinum/titanium mesh anode looks sweet :D

Yes,

axehandle - 14-4-2004 at 13:05

but I somewhat regret buying it.... I don't know how thick the Pt layer is. I'll know later though, when my H2SO4 plant is finished and I start my next project: A KCl --> KClO4 cell.

Does anyone know of an electrolytic way of increasing the Pt layer thickness, perhaps using HCl and hexachloroplatinic acid? I'd like to add a gram or one and a half...

t_Pyro - 14-4-2004 at 19:40

Pure Pt and Pt clad Ti ????? I'd KILL for that! Lucky you! :mad: Any chance of auctioning it off? Just tell me if you ever get tired of them someday- I'll buy them from you!

The Pt coating does not need to be too thick. It should just coat the entire metal surface completely and uniformly to prevent erosion.

I'd thought of electroplating using chloroplatinic acid, too. However, it won't work unless the compound exists as platinum ions in solution, which I'm not sure they do. Anyone care to enlighten us? For some info on metal plating: http://www.groupsrv.com/science/viewtopic.php?t=10129

[Edited on 15-4-2004 by t_Pyro]

The_Davster - 14-4-2004 at 19:47

Wow Axehandle, those are some incredibly beautiful electrodes you have there.:o Any chance of letting us in on which catalog these came from?

Hehe

axehandle - 15-4-2004 at 04:16

Well, I got them from a local noble metals retailer, at exhorbitant prices ('cept the Ti, which was cheap). The don't do mail order outside Sweden.

But a little bee whispered in my ear that Pt clad Ti mesh can be found cheaply at ebay.de .......

Edit: However, the Pt wire might be a little too long. I might want to sell off some in the near future.


[Edited on 2004-4-15 by axehandle]

Saerynide, darkflame89,

axehandle - 15-4-2004 at 07:16

here are the pure Pb electrodes. They are 8mm in diameter and approx. 65mm long. If you want to increase the surface area, just smash them lightly with a hammer --- since they are pure Pb, they're <b>very</b> soft.

Unfortunately, I had no PVC hose with the right diameter to seal them, but that's not impossible to buy at your location, I hope?

Darkfire - 15-4-2004 at 10:36

What a guy, way to help you fellow madscientists...

ballzofsteel - 15-4-2004 at 20:42

I dont know if this has been posted,
Sorry, if it has.Ill delete if need be.

It is related to what you guys are trying to do.
Click on the links for some interesting reading.
May aid in the quest for pure Cl2 also

Patent, US5,855,759

Abstract:
The present invention relates to an electrochemical cell and a process for producing a hydroxide solution, sulfuric acid and a halogen gas from a hydrogen halide and a sulfate solution. In particular, the sulfate solution may be an alkali metal sulfate solution, such as sodium or potassium sulfate solution, an alkaline earth metal sulfate solution or an ammonium sulfate solution. The cell and the process may use either an anhydrous or an aqueous hydrogen halide, namely, hydrogen chloride, hydrogen fluoride, hydrogen bromide and hydrogen iodide, to a respective dry halogen gas, such as chlorine, fluorine, bromine, or iodine, to produce hydrogen ions in order to split the alkali metal solution and form the sulfuric acid. The cell has two membrane-electrode assemblies, where an anode is disposed in contact with one membrane, and a cathode is disposed in contact with another membrane. The sulfate solution is fed in between the membrane-electrode assemblies.

darkflame89 - 16-4-2004 at 02:26

Amazing and beautiful electrodes:D I can hardly wait... I am currently building a voltaic pile of copper and aluminium. I hope to supply up to 12v of DC current, since Al and Cu have an EMF of 2v per cell.
i also can't decide whether to use vinegar or NaCl solution as electrolyte.

Saerynide - 16-4-2004 at 02:28

Wow. I cant wait either :D Thanks a ton.

A voltaic pile? Just for fun or seriously for a power supply? :o

darkflame89 - 16-4-2004 at 02:32

Of course to power my electrlolysis, since batteries in long term are expensive.:(

Saerynide - 16-4-2004 at 02:52

I said use a power supply! :P

Quantum - 16-4-2004 at 14:45

Your going to make a pile instead of using a PSU?:o I can get them for the cheap around here. Try seeing if someone is selling an old computer and buy it for 20 bucks. The older the better as long as it still is a PC.

Don't make a pile; it will cost you way more in time and money than its worth.

darkflame89 - 17-4-2004 at 05:47

Or i could use a power adaptor or something, but can't find one:(

darkflame89 - 19-4-2004 at 01:38

After thinking through the setup, i would like to ask a question: Does electrons move through the solutions or does ions move through the solution?

You see, in my setup earlier as shown in the previous pics, copper blue coloration, was seen in only one bowl, the anolyte. If ions were to move through the solution, then most certainly, copper ions presence will be detected in the catholyte. Correct? But in the setup in the earlier pics only in one bowl was the blue coloration seen. That means that electrons move thorugh the solution.

Then this means that magnesium ions will be left in the anolyte after electrolysis. So, the H2SO4 is not going to be pure!:o

Is there a flaw in in my logic process?

[Edited on 19-4-2004 by darkflame89]

The_Davster - 19-4-2004 at 16:22

It is the ions that move through the solution, but only certain ions. The cations move through the porous boundry to the cathode to prevent a build up of negative charge in the catholyte. The anions move through the porous boundry to the anode to prevent a build up of positive charge in the anolyte.

darkflame89 - 20-4-2004 at 00:54

Which certain ions, you mean more reactive cations will go first??

t_Pyro - 20-4-2004 at 18:07

The ions with a greater ionic mobility migrate the fastest. Ions are elctronated/de-electronated according to their concentration and redox potentials.

darkflame89 - 24-4-2004 at 00:23

Just been think about this, there is a certain electrochemical setup that is somewhat similar to the setups used here. This setup has the advantage that batteries do not need to used. Consider this: Dip lets say a piece of iron into a saturated MgSO4, and in another a bowl, a similar setup is used except instead on iron, you use say, copper. Then you connect both bowls with a salt bridge and connect both metals with wire.

This setup is a battery cell arrangement that uses the EMF between the 2 metals to provide current. I have read about this, but the book hardly say anything else except to say that electricity is produced.
But we all know that in such a setup, the iron which is more electronegative than copper becomes the negative terminal of the battery and copper becomes the positive terminal. The iron will then dissolve to form ions(I am not sure Fe2+ or Fe3+), and at the copper side, H2 gas is given of.

Of course, acid is not produced here, its just that i am hoping that that at the negative terminal acidic salts can be formed that hydrolyses to a certain degree to form acids. At the positive terminal, Mg(OH)2 will result as usual.

If one uses copper sulphate as the electrolyte in such a setup, can sulphuric acid be produced? Since copper will be discharged at the positive terminal and the negative terminal(maybe aluminium) dissolves.

Geomancer - 12-6-2004 at 13:42

Drifting gently off topic. (We really need a bunch of sulphuric acid production threads, including "H2SO4 by electrolysis", which was what I was looking for.)

Someone mentioned a long time ago that sulphuric acid could somehow oxidize sulphur. How does this go, and more importantantly, are the products electrolyticly oxidizable to H<sub>2</sub>SO<sub>4</sub>?

t_Pyro - 12-6-2004 at 17:17

I think the reaction that you're talking about is:

2H<sub>2</sub>SO<sub>4</sub> + S -> 3SO<sub>2</sub> + 2H<sub>2</sub>O

Conc. sulfuric acid is required.

[Edited on 13-6-2004 by t_Pyro]

darkflame89 - 13-6-2004 at 01:11

But does this help? I mean i have neither sulphuric acid nor sulphur at the present. I recently conducted the experiment with electrolysis using newly aquired carbon rods. The anolyte registered a pH of 2 while the catholyte registered a pH of 9. The setup ran on a 9V battery. Also, the sulphuric acid(if there was any) did not have any brown colorations unlike Saerynide's experiment. This led me to think that the brown coloration is due to the presence of MnO2.

But the disappointing thing is that, apparently the amount of sulphuric acid present is too little despite having a pH of 2. When NaHCO3 was added, no fizzing was seen, except some small bubbles produced at a slow rate.

I think that the voltage of electricity that I used is to little ( I ran the setup for 3 days!) Anyway, i will be trying the chemical method of adding phosphuric acid to MgSO4 to try and obtain sulphuric acid

hodges - 13-6-2004 at 13:25

Quote:
Originally posted by darkflame89
But the disappointing thing is that, apparently the amount of sulphuric acid present is too little despite having a pH of 2. When NaHCO3 was added, no fizzing was seen, except some small bubbles produced at a slow rate.


A pH of 2 would imply 10^-2 moles of H+ ions per liter. For H2SO4, this would be 1/(2 * 100) = 0.005 molar! That's why you are not seeing much fizzing. As a comparison, drain cleaner containing H2SO4 is somewhere around 18 molar. A pH of 2 may sound impressive, but a few drops of a strong acid in a beaker of water can produce a pH of 2.

To get 1 mole of H2SO4, you will have to run 54 ampere-hours of current through your solution. That's assuming perfect efficiency and no mixing!

Geomancer - 15-6-2004 at 11:22

The reaction from sulphur may not help those in Singapore, but for people who can get sulphur, it may. Even trapping the SO<sub>2</sub> in water solution and electrolysing, then combining pots and boiling (or electrolysing more) would give a somewhat viable route. Better would be if it worked in one pot. Something to try as soon as I get some functional sulphur.

t_Pyro - 15-6-2004 at 19:05

Eficiency might be a major problem in that method, though. Two-thirds of the SO<sub>2</sub> produced comes from the conc. sulfuric acid, so assuming all the SO<sub>2</sub> is eventually converted to sulfuric acid, to produce 1volume of "new" sulfuric acid, you need 2 volumes of conc sulfuric acid!

[Edited on 16-6-2004 by t_Pyro]

Jome - 30-6-2004 at 14:07

That method of turning sulfur into sulfuric acid sounds promising!

What if one would mix H2O2 (20-30%) with concentrated H2SO4 and then add sulfur, would the SO2 produced by the reaction you mentioned be absorbed in the water and oxidised by the peroxide directly form more sulfuric acid?
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