Sciencemadness Discussion Board

Sulfuric Acid from Oxalic Acid and Copper Sulfate: does not work

BaFuxa - 28-10-2017 at 10:09

Hi,

Today I tried making myself some H2SO4 via the oxalic acid + copper sulfate method. There are few videos on the internet claiming it a viable way to get the sulfuric.

This is totally rubbish. What you get after distilling off the water is a transparent, very acidic solution ( PH around 1) that is lighter:o:o:o than water. Needless to say it did not react with iron nor aluminum.


I have no idea what the heck this is. Sulfurous acid, bisulfite ? Some of you guys had any success with this approach ?

elementcollector1 - 28-10-2017 at 10:54

Have you perhaps tried boiling it to concentrate it?

hissingnoise - 28-10-2017 at 11:21

Your stoichiometry was off, perhaps ─ did you, for instance, get the expected precipitate?



clearly_not_atara - 28-10-2017 at 11:38

I thought it was supposed to be magnesium sulfate?

Are you sure the product is lighter than water, and not just lighter than you expected it to be? This seems to suggest an impurity IMO as nothing in the rxn mixture is lighter than water nor are the decomposition products (formic acid, carbonic acid, sulfurous acid).

SWIM - 28-10-2017 at 11:57

Quote: Originally posted by clearly_not_atara  
I thought it was supposed to be magnesium sulfate?

Are you sure the product is lighter than water, and not just lighter than you expected it to be? This seems to suggest an impurity IMO as nothing in the rxn mixture is lighter than water nor are the decomposition products (formic acid, carbonic acid, sulfurous acid).


Magnesium sulfate is definitely discussed for this purpose on some threads here and is supposed to work.

Maybe whatever you did somehow reduced the acid by oxidizing the copper?

Melgar - 28-10-2017 at 23:16

The "lighter than water" part is patently false. How did you come to the conclusion that it's lighter than water? OP seems far too sure of his own correctness to actually be correct, in my opinion.

Metacelsus - 29-10-2017 at 04:57

Quote: Originally posted by SWIM  

Maybe whatever you did somehow reduced the acid by oxidizing the copper?


I think you mean oxidizing the oxalic acid (to CO2) while reducing the copper. Copper(II) is very unlikely to be oxidized further.

BaFuxa - 29-10-2017 at 09:39

Ok ok I am just back from the shed.

First off, as for the weight ethanol is probably contaminating the solution as I distilled some before and just lightly washed my hardware.

Then you are correct, I did a stochiometry of 50/50 and upon further research I found that the correct ratio is 4/5 oxalic acid/ copper sulfate. So yes it was off. I will try again with the prescribed amounts.

What was really interesting though is that I added some 6% hydrogen peroxide to the solution and it did attack steel nails:o. I tested the steel nails with the H2O2 alone and nothing happened.
It did nothing on aluminum though, probably not concentrated enough but I think this is sulfuric acid.




[Edited on 29-10-2017 by BaFuxa]

[Edited on 29-10-2017 by BaFuxa]

SWIM - 29-10-2017 at 12:17

Quote: Originally posted by Metacelsus  
Quote: Originally posted by SWIM  

Maybe whatever you did somehow reduced the acid by oxidizing the copper?


I think you mean oxidizing the oxalic acid (to CO2) while reducing the copper. Copper(II) is very unlikely to be oxidized further.


No, actually I just had no idea what I was talking about.
Oxidation states of metals are not my strong point.:(

AJKOER - 1-11-2017 at 06:47

First, known that H2C2O4 is both an oxidizing and reducing agent!

The recommended preparation of ClO2 (which is an easily explosive gas unless diluted in an inert gas) is via chlorate + H2C2O4. The reaction proceeds:

2 KClO3 + H2C2O4 = 2 HClO3 + K2C2O4 (s)

and with more excess Oxalic acid:

2 HClO3 + H2C2O4 --> 2 H2O + 2 ClO2 (g) + 2 CO2(g)

so the net reaction is:

2 KClO3 + 2 H2C2O4 --> 2 H2O + 2 ClO2 (g) + 2 CO2 (g) + K2C2O4 (s) (source: see https://books.google.com/books?id=6wUmteTIc18C&pg=PA334&... )

The action of oxalic acid on HClO3 illustrates H2C2O4 acting as a reducing agent on chloric acid resulting in a safer mix of ClO2 diluted in CO2 gases.
---------------------

The reaction of H2C2O4 with CuSO4 proceeds as follows:

CuSO4 + H2C2O4 = CuC2O4 + H2SO4

Avoid an excess of oxalic acid as it may apparently, see below, be violently reduced by when the H2SO4 becomes concentrated.

Here are some important (safety) comments from a prior thread of mine (see http://www.sciencemadness.org/talk/post.php?action=reply&... ).
Quote: Originally posted by AJKOER  
Quote: Originally posted by Formatik  
.....
Another attempt of sulfuric acid from oxalic acid and CuSO4 (beware!):

I made another attempt with the copper sulfate and oxalic acid. But this time used larger amounts. This time I only filtered and siphoned the filtrate, and did not evaporate and collect more solids. But this time I just boiled down the filtrate. Something very bad happened on boiling near the end, all of the sulfuric acid and contents in the 600mL beaker ejected entierly! I think the sulfuric acid reacted violently with residual oxalate (another crystallization would have been good) and the heating might have been too high.

The purity of acid made this way should be alright for some purposes. CuSO4 has a solubility of 0.19g in 100g of 92.70% H2SO4 at 25 C (Solubilities of inorganic and organic compounds, 2nd ed. (1919) by A. Seidell). CuSO4 should be the end-product copper salt and the white solid that was seen earlier in the brown acid.

On another similar note, aqueous copper sulfate yields no precipitate or any reaction of note when added slowly into an excess of aqueous citric acid. The reactivity of citrates might be the reason why there is no reaction. Oxalic acid can be boiled with nitric acid and is able to partially resist the attack.
..........


Please do not attempt to push this reaction to the point where concentrated H2SO4 is formed. The violent ejection on heating, per recent research, could be from the abrupt decomposition of unreacted Oxalic acid into H2O, CO and CO2. Source: Watts' dictionary of chemistry, Volume 3, by Henry Watts, page 649 under 'Reactions'. To quote:

"-2. On heating with conc. H2SO4 or with P2O5 it is resolved into water, CO and CO2."

Link: http://books.google.com/books?pg=PA649&lpg=PA649&sig...

[Edited on 7-8-2012 by AJKOER]


[Edited on 1-11-2017 by AJKOER]

MrHomeScientist - 1-11-2017 at 07:13

If you post more details on amounts, procedure, how you tested the products, etc. we can be much more helpful. It's hard to give good advice when the report is "it didn't work". Assuming you followed an established procedure, I'd agree that low concentration may explain why it doesn't readily react with metals. Aluminum isn't a great choice for a test because of its oxide layer, which can greatly slow reactions.