Thulium - 25-3-2018 at 23:40
Hello all!
I've had the good fortune to produce sodium perchlorate and potassium chlorate using electrolysis (platinum electrodes, current regulated power
supply), and have begun to wonder if electrolysis could be used to produce some more interesting reagents along the same theme.
The first: perchloric acid via electrolysis of HCl. There are a number of patents floating around on the subject, and I know this is how perchloric
acid is produced industrially, but I worry it may not be suitable for home due to intermediaries. If the temperature of the solution is kept warm, it
seems this setup will be more apt to produce chlorine gas since it won't stay in solution. If the solution is kept cold, my concern is that the
intermediary chloric acid may reach high enough concentrations (heat encourages chloric acid disproportionation) to have unpleasant effects like
reacting explosively with the hydrogen gas emitter at the cathode. If anyone has tried this, I would love to hear the details of the procedure.
In a similar vein, rather than producing sodium perchlorate and reacting with an ammonium salt, could AP be directly synthesized from electrolysis of
ammonium chloride. At first glance, it seems like an attractive idea since AP is relatively low in solubility and should precipitate out nicely.
However, I suspect this may be a very bad idea due to side reactions with chlorine and ammonia producing nasty chloramines/NCl3 or the possibility of
NH4ClO3 precipitating out (I cannot find any data on its solubility.. I wonder why 
) If anyone has any thoughts on this approach as well, please let me know!
Thanks!
woelen - 25-3-2018 at 23:59
HClO4 from HCl by means of electrolysis? I do not believe that, also not in an industrial setting. This reaction cannot go through a chloric acid
intermediate, because chloric acid and HCl react quickly and completely, to a mix of Cl2 and ClO2.
HClO4 is made from HCl industrially, but it is done by adding NaClO4 to HCl. The NaClO4 is made by means of electrolysis. This in turn is added to
conc. HCl. NaCl precipitates and HClO4 remains behind in solution, together with some remaining HCl. The liquid then is boiled down, causing HCl to be
driven off and precipitating more of the NaCl. The resulting acid, however, never will become completely free of Na(+) ions. Other techniques are used
to get rid of these Na(+) ions. For the home chemist, however, the method of making HClO4 from NaClO4 and conc. HCl is quite interesting. Having a
little Na(+) ions in the acid is not that bad, this does not interfere with most experiments.
Ammonium chlorate and ammonium perchlorate cannot be made by means of electrolysis of NH4Cl. At the cathode you get formation of NH3 besides H2. At
the anode you indeed may get some NCl3. Do not expect any formation of NH4ClO3 or NH4ClO4.
If you want creation of other interesting salts by means of electrolysis, try making KBrO3 and KIO3. I made both of these, using a platinum wire. It
works quite well. I used a small cell and just made several grams, but you can easily scale up:
http://woelen.homescience.net/science/chem/exps/KBrO3_synth/...
Thulium - 26-3-2018 at 09:06
Hello Woelen,
Great guide on the KBrO3 / KIO3! Many thanks! I will have to give that a try and dig out that old book from the seventies on oscillating reactions I
know I have somewhere in my basement
I found that patent I referenced earlier with respect to HCLO4 via electrolysis. https://patents.google.com/patent/US1271633 and it seems that while it "works", it's horribly inefficient and only produces dilute solutions. It
looks like an improvement can be made utilizing a solution of chlorine in dilute HClO4 added to improve conductivity. https://patents.google.com/patent/US2846383A/en with careful attention added to temperature to keep the dissolved chlorine levels as high as
possible (the patent recommends 0 C)
Another "may have to try", if I can figure out something to coat the wires above the electrodes in that Cl2 won't attack.
Probably not as practical as the old strong acid + NaClO4 method, but I imagine most of us here are curious about new procedures