lupy
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chlorate
ive been running a succesfull chlorate cell for some months now. The anode is 1 mm platinum wire and the cathode is 2mm titanium wire. The titainium
has started to fall off in spinters! after searching the net i discovered its caused by hydrogen embrittlement - above 80 C H2 gets aborbed into the
surface of the titanium and forms titantium hydride. This somehow makes its really brittle. I guess i;m running the cell too hot or something. Perhaps
stainless steel will not do this.
What i don't understand is why my platinum anode, tho appearing untouched where its under solution, is looking affected above the water line.
Its also where salt or chlorate or something crystallises on it.. probably from being thrown up in droplets and evaperation. Is the god of metals
affected by chlorine or salt or when both are together? what is happening to my expensive anode?? hehe
btw its a 500ml cell which i run for 3 days at 6 A. Produces good yeilds of chlorate. Temp is between 80 and 90 most days.
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axehandle
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I'm going to build a similar device; just waiting for my 300mm long, 0.8mm thick pure Pt anode to arrive. I originillaly aimed for 1.0mm, but
found the cost too prehibitive.....
I'm going to run the Pt folded over to decrease electrical resistance heating. I intend to use a deep 18-10 stainless steel canister acting both
as the electrolysis vessel and as the cathode.
The Pt wire will form a loop close to the surface of the KCl solution.
About your chloride question: Pt shouldn't be attacked by chlorine unless it's HCl in aqua regia. But if I were you, I would dip the
non-submerged portion of the Pt wire in hot melt glue just to be on the safe side. That's what I'm gonna do.
Btw, what voltage are you using?
[Edited on 2004-2-17 by axehandle]
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lupy
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voltage
oops... forgot about this post. I use about 6.6 volts and around 6.2 amps into 500 ml . My supply is kinda current regulated so the voltage rises to
maybe 7 towards the end. I tried a stainless steal cathode recently but its corroded above the solution and contaminated it. Dont know what grade of
stainless steal is was tho. Id recommend titanium as long as u keep the temp below 80 C! Perhaps some grades of stainless steal work well... havent
tried.
lupy
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axehandle
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Ok thanks. I'm going to use a PSU that's capable of 30A at 5V (ATX power supply....).
As for the cathode being corroded above the "waterline", I think some high-temp barbecue grill paint would protect it, no?
Edit: Not even the largest welding supplier here in town has titanium rods on the shelf, they have to be ordered! Really sucky, IMNSHO.
[Edited on 2004-2-18 by axehandle]
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Organikum
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axehandle wrote: | Quote: |
Pt shouldn't be attacked by chlorine unless it's HCl in aqua regia
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Pt dissolves slowly if in aqueous HCl and AC is run on the (Pt) electrodes. No enormous voltage or current needed - the usual voltages/current as used
in organic electrosynthesis suffice.
I found this in an old article on the usability of AC in organic synthesis and thought it might be useful for somebody who wants to dissolve Pt
without the need of aqua regia - as precursor of catalysts or else.....
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Turel
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Pt+3/Pt+4?
Organikum, when Pt is dissolved in this manner, what species is in solvation? Is it Pt+3, Pt+4, or some wacko coordination complex?
-T
[Edited on 19-2-2004 by Turel]
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axehandle
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I think it might be species 8472, in disguise... 
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Organikum
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I am rather sure that hexachloroplatinic (IV) acid is formed so enough water is present.
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axehandle
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Organikum: Are you absolutely sure about this?
If you're right, I could make Pt-on-diatomaceous without nitric acid, since HCl is one of the few acids not regulated here.
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Organikum
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Canadian Journal of Research
Vol. 17. SEC. B.
May 1939
Number 5
The electrolysis of some organic Compounds with alternating current.
by J. W. Shipley and M. T. Rogers
It is stated that Pt electrodes get slightly attacked in these electrolyises.
In the chapter on chlorinations it is explicitely told that the Pt electrodes slowly dissolve. High current densities seem to vavor this.
If already at the rather low current densities and voltages of organic reactions a watchable dissolving of the Pt electrodes over a few hours takes
place, there can be no doubt that you can dissolve Pt with ease by this way using:
- more time
- higher current/voltage
- the last requires COOLING of course.
Answers:
- Yes I am sure on this.
- Thats exactly why I posted the information.
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axehandle
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Organikum: Amazing. You just saved me from ordering $50 worth of V2O5. Will you
marry me?
By the way, I know citing sources is a no-no here, but this one is totally inconspicious.
Diatomaceous earth (kiselgur, fossilized algae) is used as a nutritional supplement for horses. Any shop that carries "horse supplies" (nice one) should have it, and it's not expensive at all, something like
$10/500g.
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Organikum
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V2O5 if not freshly precipitated is quite inactive as catalyst btw. So ordering a vanadium compound from which V2O5 can be easily precipitated might
be a better idea.
This board has no rule and no policy against the posting of "sources", say naming firms and places where legal compounds can be legally
aquired.
I guess you confuse this with some other places.... 
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axehandle
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Yes, someone mentioned NH4VO3 absorbed in pumice, then glowed. But where would I get NH4VO3? "Ammoniumvanadintetraoxide" doesn't sound
like something you can just buy OTS.... 
Edit: Just melted some brass in my desktop furnace. I might have overheated it. Can't stop coughing. If I manage to stay alive, I'll try to
find a source or a method of synthesis, preferably from V2O5.
I really have to buy some books on synthesis of obscure precursors......
[Edited on 2004-2-19 by axehandle]
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Polverone
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"Vanadium salts may be obtained from mottramite by digesting the mineral with concentrated hydrochloric acid, the liquid being run off and the
residue well washed; the acid liquid and the washings are then evaporated with ammonium chloride, when ammonium metavanadate separates. This is
recrystal-lized and roasted to vanadium pentoxide, which is then suspended in water into which ammonia is passed, when ammonium metavanadate is again
formed and may be purified by re-crystallization."
(from <A HREF="http://1911encyclopedia.org">1911 Encyclopedia</A>
See what sorts of great information you can find on the web? 1911encyclopedia.org is a wonderful source for basic, applied chemical information. Like
many of the other best Web resources, it is an electronic copy of a work that was originally published on paper.
It seems like many of the transition metal "-ates" can be prepared by treating their oxides with various strong alkalis or oxidizing agents,
or a mixture, often at elevated temperatures.
Fe2O3 + KNO3/KOH --fusion--> potassium ferrate
Cr2O3 + KNO3/K2CO3 --fusion--> potassium chromate (acidified, gives dicromate)
MnO2 + KOH/KNO3 --fusion--> potassium manganate (acidified, gives permanganate)
V2O5 + KOH --fusion--> potassium vanadate
[Edited on 2-19-2004 by Polverone]
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axehandle
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Thank you! I just googled in vain and here you come and give me the answer..... thank you again.
Edit: I interpret the information as such, that V2O5 in water with ammonia forms NH4VO3,
then you simply boil off all fluid and then glow it to get the V2O5 back. Seems easy enough. Provided that "ammonium metavanadate" is the
same as NH4VO3...
Edit2: Which it is. "Ammonium metavanadate is obtained when the hydrated vanadium pentoxide is dissolved in excess of ammonia and the solution
concentrated. It has been used in dyeing with aniline black."
That process must be reversible.
I'm one step closer to my ultimate goal: An H2SO4 machine fitting on a desk, using air, sulfur and electricity (for heating the catalyst) as its
only fuel.
Edit3: Still not sure whether to use V2O5 or Pt..... Pt is more expensive and the catalyst must be heated a couple of hundreds of degrees more, and
it's slowly poisoned by sulfur....... on the other hand, I soon have some Pt wire...... well, 100g of V2O5 shouldn't cost more than approx.
$20 + freight, so....... I'll have to think about it.
I'm wondering if I'm the first to think of having the catalyst inside a 20mm glass tube, heating it by means of nichrome wire spiralled
around it, current controlled by a light dimmer..... with a thermocouple connected to the tube for adjusting the dimmer so that the temp gets just
right for the catalyst.
[Edited on 2004-2-19 by axehandle]
[Edited on 2004-2-19 by axehandle]
[Edited on 2004-2-20 by axehandle]
[Edited on 2004-2-20 by axehandle]
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Organikum
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I actually only know the precipitation of V2O5 from the nitrate...
... probably the ammoniumvanadate works too, dunno.
Stupid question:
Doesnt electrolysis of metalsulfates produce sulfuric acid?
I was sure electrolytic zinc is made by means of the sulfate and what if not sulfuric acid should be produced when metallic zinc is formed.
But I am very tired so excuse me if this is far out....
...good night.
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BromicAcid
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| Quote: |
Pt-on-diatomaceous without nitric acid, since HCl is one of the few acids not regulated here.
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I would guess that low temperature AC electrolysis of Pt would solovate it. Being that in aqua regia the nitric dissolves only a miniscule amount of
Pt, it is the HCl that takes what is dissolved and puts it in a form that will stay in a solution to move the equilibrium. I'm sure that the
small amounts of chloric and perchloric acids should be strong enough oxidizing agents to dissolve tiny amounts of platnum and the excess HCl should
do what it normally does.
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Saerynide
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kinda off topic.... but
it pertains to the original topic of this thread 
Does stuff happen to solutions of sodium hypochlorite/chlorate? I had a solution of a mix of the two, before it was yellowish greenish (this was a
few months ago), now its almost colorless. Did it like auto-oxidize or break down or something? 
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Marvin
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In the contact process for sulphuric acid sulphur does not poison the catalyst. In industrial settings this is usually a problem with arsenic.
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