Sciencemadness Discussion Board

Need an easy synthesis of Perchloric acid

Rhodanide - 18-7-2017 at 14:11

Hi, all.

I need a simple, straightforward, no-complicated-bullsh*t synthesis of Perchloric acid. I'm trying to make Tetraammine Copper Perchlorate. I tried making anhydrous Perchloric acid two weeks ago, and ended up making my porch look like a second-hand smoke machine store. Not only that, but I had unknowingly made Hydronium perchlorate, but destroyed and disposed of it before I knew what it was. I don't want anhydrous perchloric acid. I don't want to distill anything preferentially, but it's still something I'm more than capable of doing. I have probably 300-500g of KClO4 left. I'd really appreciate a reply.

Metacelsus - 18-7-2017 at 14:24

Distillation is the best way, especially because potassium perchlorate is relatively insoluble (so strategies analagous to those using sodium perchlorate and HCl won't work). If you make your starting solution sufficiently dilute, you'll be able to distill off the azeotrope and not worry about the anhydrous acid.

Rhodanide - 18-7-2017 at 15:22

Quote: Originally posted by Metacelsus  
Distillation is the best way, especially because potassium perchlorate is relatively insoluble (so strategies analagous to those using sodium perchlorate and HCl won't work). If you make your starting solution sufficiently dilute, you'll be able to distill off the azeotrope and not worry about the anhydrous acid.


The azeotrope is 70%, no?

feacetech - 18-7-2017 at 16:54

thats the common concentration I buy it at

[Edited on 19-7-2017 by feacetech]

Rhodanide - 18-7-2017 at 17:07

Quote: Originally posted by feacetech  
thats the common concentration I buy it at

[Edited on 19-7-2017 by feacetech]

Where do you buy it?

BromicAcid - 18-7-2017 at 19:12

Massive threads on perchloric acid around here, take a look. You'd be interested in either gassing sodium perchlorate aqueous solution with hydrogen chloride. This crashes out the sodium chloride from common ion effect and then you filter and heat to drive off HCl and water to leave you with perchloric acid. The more insane method involves mixing ammonium perchlorate with nitric acid (IIRC) and heat the snot out of it feeding it more nitric to oxidize your ammonium cation to gaseous products leaving behind perchloric acid. Just to give you some direction, you will need to read much more into it. Perchloric acid is insidiously oxidizing, research, research, research, and take care.

hissingnoise - 19-7-2017 at 11:55

IIRC, KClO4 is the least soluble of the perchlorates ─ and that's something of a stumbling block!

hissingnoise - 19-7-2017 at 12:39

It's quite easy to distill from 72% H2SO4 to give a perchloric acid soln., BTW!

feacetech - 19-7-2017 at 14:42

Quote: Originally posted by Tetra  
Quote: Originally posted by feacetech  
thats the common concentration I buy it at

[Edited on 19-7-2017 by feacetech]

Where do you buy it?


with great difficulty if your a layman

I have an industrial QC lab, its a tracked substance in my country and requires hadnling certification to buy it as well

woelen - 21-7-2017 at 12:08

Quote: Originally posted by BromicAcid  
Massive threads on perchloric acid around here, take a look. You'd be interested in either gassing sodium perchlorate aqueous solution with hydrogen chloride. This crashes out the sodium chloride from common ion effect and then you filter and heat to drive off HCl and water to leave you with perchloric acid.

This works very fine. You can even do it simpler. Take some 35% HCl and add a very concentrated solution of NaClO4 to it. Use excess HCl. Nearly all sodium settles as NaCl. If you want to get rid of the last bits of Na(+) ions, then heat a little more of the 35% HCl and lead the gas through your solution. But in my experience this hardly is necessary.
The liquid is a mix of HClO4 and HCl and the latter can be boiled off. Just boil the stuff until the liquid gets 150 C or so. At that temperature you have driven off a lot of water and all of the HCl. What remains is appr. 65% HClO4. You can get to 70% but then you should go much further, well over 200 C, and I do not like that with such concentrated HClO4.

Quote: Originally posted by BromicAcid  
The more insane method involves mixing ammonium perchlorate with nitric acid (IIRC) and heat the snot out of it feeding it more nitric to oxidize your ammonium cation to gaseous products leaving behind perchloric acid.
I tried this as well. This is totally crap. The only thing I did was spoiling lots of HNO3 and fuming the room like crazy with HNO3, but I did not get anything even remotely like pure HClO4. On cooling down, the liquid deposits a lot of crystal matter and guess what? It is NH4ClO4. Truly a pity. The only perchlorate we can get is NH4ClO4. NaClO4 is forbidden in the EU. NH4ClO4, however, is much less useful for most home chemistry experiments than NaClO4. From NH4ClO4 you can make NaClO4 with NaOH and a few drops of water. NH3 is produced and NaClO4 remains behind.

Starting from KClO4 is really problematic. KClO4 is the least useful perchlorate for anything else than pyrotechnics. It is only very sparingly soluble in cold water and the only way to release the perchlorate from this is distilling it with sulphuric acid, but in my opinion this distillation is too dangerous for an average home lab.

clearly_not_atara - 21-7-2017 at 16:09

Quote: Originally posted by Metacelsus  
Distillation is the best way, especially because potassium perchlorate is relatively insoluble (so strategies analagous to those using sodium perchlorate and HCl won't work). If you make your starting solution sufficiently dilute, you'll be able to distill off the azeotrope and not worry about the anhydrous acid.

Far easier though to convert to the sodium perchlorate by metathesis with a concentrated solution of sodium bitartrate.

Solubility:

KClO4 1.5 g / 100 mL (25 C); 21.1 g / 100 mL (100 C)
KHTrt 0.6g / 100 mL (20 C); 6.1 g / 100 mL (100 C)

Converting K tartrate to the sodium salt may prove tricky, however it can be accomplished by first converting it to Rochelle salt and then treating a solution of this with CaCl2, precipitating calcium tartrate, which is then treated with sulfuric acid (actual route), or, possibly, with phosphoric acid (fingers crossed), yielding tartaric acid which is then half-basified.

[Edited on 22-7-2017 by clearly_not_atara]

[Edited on 22-7-2017 by clearly_not_atara]

AJKOER - 23-7-2017 at 11:45

A possibly more accessible (?) path for those without a perchlorate to start, or having depleted ones supply of perchlorate, is via the action of blue light on a mix of Cl2 and O3 forming Cl2O7. Source, see " THE FORMATION OF CHLORINE HEPTOXIDE ON ILLUMINATION OF MIXTURES OF CHLORINE AND OZONE", by A. C. Byrns and G. K. Rollefson, published in Journal of the American Chemical Society, Vol. 56: , Issue. 5, : Pages. 1250-1251,1934. Link: http://pubs.acs.org/doi/abs/10.1021/ja01320a506 .

The action of water on dichlorine heptoxide forms perchloric acid:

Cl2O7 + H2O = 2 HClO4

See also Wikipedia comments regarding safety issues at https://en.m.wikipedia.org/wiki/Dichlorine_heptoxide .
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An interesting experiment would be a small scale (safety issues) electrolysis of a cold (10 C) alkaline (pH 9.4) chlorate solution with an RuO2/TiO2 anode. Related research, please see https://www.researchgate.net/publication/256697280_On_the_el... .

My opinion is possible perchlorate formation based simply on the following radical pathway given the generation of hydroxyl radicals (.OH) by such an electrode:

ClO3- + .OH = .ClO3 + OH-

.OH + .ClO3 = HClO4 ( See https://www.google.com/url?sa=t&source=web&rct=j&... )

Unfortunately, there may be reductive reactions limiting yield. However, related photolysis paths based on aqueous suspensions of TiO2 (or MgO, ZnO,...) may fare better. This occurs even in the case of starting with dry chlorides to a very limited extent with time, see "PHOTOOXIDATION OF CHLORIDE TO PERCHLORATE IN THE PRESENCE OF TITANIUM DIOXIDE AND DESERT SOILS", by Miller, et al, preview available at: https://www.google.com/url?sa=t&source=web&rct=j&... .

Note, using an alkaline solution mitigates (but not eliminates) the possible incidental formation of explosive gases (like ClO2).

[Edited on 24-7-2017 by AJKOER]

Rhodanide - 24-7-2017 at 09:14

Geez, thank you all for the info. Awesome!
If I have no luck making it in the ways you all described, I'll see what Mario can do about finding me some ;]

Rhodanide - 24-7-2017 at 09:21

Just looked at the prices on Sigma, and my goodness it's expensive! 200+ dollars USD for 500mL?! Maybe it's more cost efficient to just make it. :O

Elemental Phosphorus - 24-7-2017 at 14:03

I would be very cautious of anything that generates chlorine heptoxide.

I also read a few U. S. patents involving methods of hydrochloric acid electrolysis and anodic oxidation of aqueous chlorine. It appears weak perchloric acid can be generated by direct electrolysis of very dilute hydrochloric acid (about 1N) using graphite, 'fused magnetite', or platinum anodes at a current density of 0.1 amps/ square centimeter to 0.5 amps per square centimeter and a temperature below 50 degrees Celsius.

Once you have obtained weak perchloric acid solution, another method is to dissolve chlorine in it. Using a platinum anode and copper cathode you can anodically oxidize the chlorine to perchloric acid.

The first method is detailed in U. S. patent 1,271,633: https://www.google.com/patents/US1271633

The second method is detailed in U. S. patent 2,846,383: http://www.google.com/patents/US2846383

AJKOER - 26-7-2017 at 05:10

Quote: Originally posted by Elemental Phosphorus  
I would be very cautious of anything that generates chlorine heptoxide.

I also read a few U. S. patents involving methods of hydrochloric acid electrolysis and anodic oxidation of aqueous chlorine. It appears weak perchloric acid can be generated by direct electrolysis of very dilute hydrochloric acid (about 1N) using graphite, 'fused magnetite', or platinum anodes at a current density of 0.1 amps/ square centimeter to 0.5 amps per square centimeter and a temperature below 50 degrees Celsius.

Once you have obtained weak perchloric acid solution, another method is to dissolve chlorine in it. Using a platinum anode and copper cathode you can anodically oxidize the chlorine to perchloric acid.

The first method is detailed in U. S. patent 1,271,633: https://www.google.com/patents/US1271633

The second method is detailed in U. S. patent 2,846,383: http://www.google.com/patents/US2846383


I agree with the caution warning! The formation of concentrated HClO4 (over 70%) from Cl2O7 and say water vapor is ill advised. See Wikipedia comments on HClO4 at https://en.m.wikipedia.org/wiki/Perchloric_acid.

AJKOER - 30-7-2017 at 05:10

The following path I personally view as potentially very unsafe but with possibly higher yields. It is based on government research noting the creation of perchlorate based on the acidified disproportionation of chlorate with the action of strong H2SO4 on NaClO3. Yields are 25% with 70% H2SO4 at 93 C and 88% yield with 83% H2SO4 at 69 C. Reference: "DISPROPORTIONATION OF SODIUM CHLORATE IN ACID SOLUTION" by H.C. Miller, et al., available at https://www.google.com/url?sa=t&source=web&rct=j&... .

Cited reaction:

3 NaClO3 + 2 H2SO4 = NaClO4 + 2ClO2 (g) + 2 NaHSO4 + H2O

Note: This paper is not oriented to the general public and key safety issues, known by professional, like the need to dilute the ClO2 with an inert gas (filtered air) to avoid an explosion are not mentioned. As such, those implementing the synthesis in this work should further research and/or consult with professionals.
-----------------------------------------------------------

Interestingly, my speculation on performing the above likely dangerous reaction absent available concentrated H2SO4 may be possible by substituting for concentrated sulfuric scid with a mix of weak H2SO4, FeSO4, some CuSO4 and an air pump providing a source of O2.

Logic: Per a source (see Werner Stumm and G. Fred Leed work "Oxygenation of Ferrous Iron", available at https://www.google.com/url?sa=t&source=web&rct=j&...), the claimed reaction:

Fe(ll) + 1/4 O2 + 2 OH- + 1/2 H2O = Fe(OH)3

Or, as: 2 H2O = 2 H+ + 2 OH- , I would restate the net reaction as:

Fe(ll) + .25 O2 + 2.5 H2O = Fe(OH)3 + 2 H+

Or, upon rescaling:

4 Fe(ll) + O2 + 10 H2O = 4 Fe(OH)3 + 8 H+

Note, a claimed catalyst for the above reaction is a small amount of cupric (like CuSO4). So, adding FeSO4/O2/CuSO4 could remove water and possibly increase H2SO4 presence, thereby fostering the formation of perchlorate.

[Edited on 31-7-2017 by AJKOER]