| Pages:
1
..
17
18
19
20
21
..
47 |
Rosco Bodine
Banned
Posts: 6370
Registered: 29-9-2004
Member Is Offline
Mood: analytical
|
|
magnetite related
Don't remember if you have this one posted or not ,
but it may reduce or eliminate the annealing requirement .
I have seen other patents also say that it is beneficial to the conductivity to have ratios for the mixed oxides that are a little away from the exact
stoichiometry for compounds like magnetite , spinel , perovskite , ect.
Attachment: US931513 Cast Magnetite Anode using crystallization modifiers.pdf (117kB)
This file has been downloaded 931 times
|
|
|
12AX7
Post Harlot
Posts: 4803
Registered: 8-3-2005
Location: oscillating
Member Is Offline
Mood: informative
|
|
My first PbO2 plating attempt
It turns out lead acetate does produce PbO2.
It's just that it produces a shitload of stringy dendritic crystals that would be beautiful if I wanted them, and razor-sharp if they were anything
other than lead. I got this result before, but didn't notice that PbO2 formed because it's as black as the graphite anode I started with. I tried
this with a dash of thiourea (to smooth out the cathode deposit), to no avail (at least at the current density I was running).
The reactions are:
Anode: Pb(2+) + 2 H2O --> PbO2(s) + 2 e- + 4 H+, Eo = 1.46V (this will be higher in an acetate solution, since it's rather hard to get 4M H+ from
acetic acid...)
Cathode: Pb(2+) + 2e- --> Pb(s), Eo = 0.13V
Acetate spectates (though one could make the argument that peracetate is made and that produces PbO2, but I don't know what the potential is), and it
appears OH- doesn't need to be involved, which makes sense, since this all works in acid solution.
As lead is consumed, acetic acid is produced (my remaining solution is stanky!), so lead hydroxide or carbonate (preferrably, well purified
material) could be added. And that's all fine and dandy, up until the lead stringers short the cell and make it boil away (yes, last night I left the
cell running; 16 hours later I find the liquid level about 30% of what it was, and the electrodes quite warm).
So why doesn't the lead metal plate out of a nitric solution? Or, does it, and no one talks about it? Seems to me it kind of HAS to happen.
I was running at somewhere between 2 and 4V. I didn't measure it at the electrodes. Current was probably a few amps. Cathode was some tangled
copper wire.
Anyway, pictures, ah, yes, sure...
Tim
[Edited on 6-25-2007 by 12AX7]
|
|
|
12AX7
Post Harlot
Posts: 4803
Registered: 8-3-2005
Location: oscillating
Member Is Offline
Mood: informative
|
|
In the above picture, you can clearly see the strained areas that delaminated from the graphite. The bottom end, due to gravity and evaporation of
the solution, is about 1/8" thick. The surface over the wider area is lustrous, while the bottom end is botrydial with an average diameter of less
than 1/32" (~1.5mm).
In this picture, the gray color is most likely the sky shining off the lustrous area. The material, overall, really is about the same black as the
graphite it's on.
Tim
[Edited on 6-25-2007 by 12AX7]
|
|
|
dann2
International Hazard
Posts: 1523
Registered: 31-1-2007
Member Is Offline
Mood: No Mood
|
|
Copper Nitrate saves Lead Ions
Hello,
Copper Nitrate is added to Lead Nitrate plating bath to stop Lead from being deposited on the cathode.
I received the following explanation some time ago.
It in on me page.
________________________
The function of Copper Nitrate in the plating bath is to stop Lead metal from plating onto the cathodes and wasting Lead ions.
If I understand this process correctly, the Copper(Nitrate)
is added to the solution in order to plate out
first. After this initial Copper plating at the
cathode, some Lead will start to deposit, but due
to the fact that there is already a layer of
Copper on the cathode, the Lead and Copper will
form a shorted galvanic couple, and the Lead,
being placed above Copper in the electrochemical
series, will be corroded or re dissolved. This
couple can supposedly also cause Hydrogen to be
evolved at the cathode, instead of any metal
plating out. I have always used a cathode with a
larger area than the anode being plated in order
to (hopefully) allow the Lead deposited there to
be re dissolved as fast as it forms. I do not know
of any magic area ratio, but I suppose you could
expect some unusual things to happen if you used a
very small cathode.
There is no need for to use Copper Nitrate if you are using a 'high' Nitric acid (100g/l HNO3) bath
____________________________________________
Perhaps you can add Copper Acetate to your plating bath to stop the Lead from being wasted.
The coating of Lead Dioxide on the Graphite that is in the pictures (I take no pleasure in being the bearer of bad news) will not protect the graphite
from (Per)Chlorate solution.
Would stirring the plating solution help.? It seems that the plating is worse as you get to the bottom of the anode.
Dann2
|
|
|
Xenoid
National Hazard
Posts: 775
Registered: 14-6-2007
Location: Springs Junction, New Zealand
Member Is Offline
Mood: Comfortably Numb
|
|
Hi Tim,
A while back I too had an experimental go at plating a graphite rod using lead acetate solution and a Ti cathode. The plating looked OK whilst wet,
but flaked off when dry. I used a current of about 5 mA/cm2, I later came across a paper where the authors were talking about 30 A/m2 being a HIGH
plating current. By my calculations thats only 3 mA/cm2. So maybe PbO2 plating needs to be carried out at only 1-2 mA/cm2. Incidently the back of my
anode where the current would have been lower, had started to develop a well bonded multi-coloured hue suggestive of a thin oxide layer!
Regards, Xenoid
|
|
|
12AX7
Post Harlot
Posts: 4803
Registered: 8-3-2005
Location: oscillating
Member Is Offline
Mood: informative
|
|
Yeah, I got some iridescence on the layer. Little was visible at the time I took the pictures above.
FWIW, I have since scraped off most of the PbO2, adding it to my pile of the stuff (it's by far the blackest; the next most recent produce, from a
divided cell anodizing on lead ingot, was darker brown than stuff I made previously, but brown nonetheless). What remains on the graphite appears to
be well bonded. I suppose a reducing agent will be necessary to remove it (HCl I guess, but it doesn't go with lead very well).
If it forms a couple with copper, that doesn't make sense because my cathode IS copper wire! Cathode area is a good point though. BTW, the lead
acetate I'm using was still green from copper impurity, although that isn't really saying much given the strength of the color.
Right now, I'm trying a stainless anode (about 1" wide, 3" long, 18 gauge, probably 304 or 316) with a copper strip cathode (almost the same
dimensions; flattened 1/2" flexible tubing). I noticed the solution turning deep orange around it (in a few minutes, with some stirring, the solution
had changed color noticably, so the color is strong), so I've pulled it out to only 1/4" submerged (if it doesn't fall over farther).
I had attempted to prepare the anode, first by cleaning it (sandpaper, detergent and then isopropyl alcohol), then I heated it red hot to attempt to
grow a layer of Cr2O3 or Fe3O4. The color is varying iridescent shades of gray.
Tim
|
|
|
Rosco Bodine
Banned
Posts: 6370
Registered: 29-9-2004
Member Is Offline
Mood: analytical
|
|
electrolytically etching stainless steels
Stainless steel is something which might be possible to use as a substrate , and I found an interesting patent which
could be useful in preparing it for use as a substrate .
The process was intended to be used for manufacturing
filtering screens by etching tiny holes completely through
a very thin 3-5 thousandths inch stainless steel sheet ,
by selectively dissolving out the grain boundaries and leaving mostly a sheet of chromium having 15 thousand
holes per square inch . But I was thinking that if a thicker material was used , it would simply etch many tiny cavities
all over the surface .....like so many crevices a few thousandths of an inch deep , which should provide good adhesion for any conductive intermediate
layer or plated on
lead oxide . Perhaps a hydriding treatment and then a tin oxide doped with antimony could be applied the same way
as would be done with titanium , followed by PbO2 .
Or maybe the electrodeposited cobalt oxide and then a
baked cobalt oxide , followed by PbO2 .
Anyway it seemed like it might be worth a try , since
the process of etching the stainless deliberately as a pretreatment would sure get rid of whatever was most easily corroded first .....leaving
something of an already
pre-corroded substrate , the legacy of which is a porous
substrate which might have a tenacious grip on subsequent coatings keyed into its crevices .
[Edited on 26-6-2007 by Rosco Bodine]
Attachment: US3352769 Electrolytically Etched , pitted , and MICROPERORATED Stainless Steel.pdf (266kB)
This file has been downloaded 698 times
|
|
|
hashashan
Hazard to Others
Posts: 255
Registered: 10-10-2006
Member Is Offline
Mood: No Mood
|
|
12AX7 i once had the same results as you did. and i do have advice for you. first do add copper ions because of what dann2 explained to you. I always
add a lot of copper ions because after all your copper is deposited the lead begins to deposit and for some reason it doesnt redisolve like dann said.
Also you use an unbelievably high current. i use 3V with quite a resistor attached to it(i dot remember what is its value, but i never plate above
200ma
|
|
|
Rosco Bodine
Banned
Posts: 6370
Registered: 29-9-2004
Member Is Offline
Mood: analytical
|
|
more concerning baked cobalt oxides
From everything I have been reading , it looks like
that if a titanium substrate is going to be used ,
and if precious metal dopants are to be avoided ,
then there are very limited choices of what intermediate
oxide layers can be used to prevent passivation of the titanium . Tin oxide doped with Antimony oxide is the cheapest , but builds slowly and
involves some tedious
preparation of the chlorides which must be applied as an
acidic solution .
Cobalt nitrate is much more soluble and may be applied
directly to the titanium and baked , and it builds thickness
faster , while producing a conductivity on par or even better
than the antimony doped tin oxide .....but does this as a single substance . Additionally another conductive cobalt oxide can be electrodeposited ,
and *if* these different
oxides can be applied sequentially , then a thick deposit can be achieved easily . The baked coating alone may be a durable enough anode for
perchlorate production , and if not then it could likely be overplated with PbO2 .
In the attached patent US4115239 see Example #2 where a direct coating of titanium with Co(NO3)2 is described as being
used for the interface layer between the titanium substrate and a modified cobalt oxides working coating . The conductivity is excellent even at
curent densities twice what
would be used for perchlorate production . The conductivity is on par (or better) than the ruthenium oxide performance , yet cobalt is far less
expensive and it evidently has better conductivity than the tin oxide , while being easier to prepare the cobalt nitrate reagent and faster to build
up thickness of the baked oxide .
Cobalt oxide looks very promising as a perchlorate cell anode material or intermediate material in several respects .
Attachment: US4115239 Baked Co(NO3)2 Direct Coated Titanium anode.pdf (66kB)
This file has been downloaded 1051 times
|
|
|
Eclectic
National Hazard
Posts: 899
Registered: 14-11-2004
Member Is Offline
Mood: Obsessive
|
|
Damn, Rosco. What am I going to do with all my solder chloride? 
I'm going to have to dissolve some more scrap carbide in HCl with electricity now to get some Cobalt salts.
If anyone needs an acid solution of SnCl2 or SnCl4, I can report that dissolving any of the common lead free solders in hydrochloric acid seems to
yield a fairly pure, water white solution of SnCl2. The alloying elements do not seem to dissolve without adding H2O2 and remain as a dense
precipitate. It's not particularly tedious, just time consuming, as it takes about 12 hours to dissolve a 1lb wad of solder in 1 liter of 10-12N HCl
at 90-95C (over simmering water bath).
Shapiro Supply on Ebay is a good source of titanium cut to size at about $10/lb.
|
|
|
Rosco Bodine
Banned
Posts: 6370
Registered: 29-9-2004
Member Is Offline
Mood: analytical
|
|
HeHeHe , you can still use dopey(sp.?) tin as an intermediate layer if you can
spare a couple of tenths of a volt overhead
Actually its a price that might have to be paid if the chemical resistance of the cobalt oxides doesn't pass tests in a perchlorate cell . But it
looks like for at least the first layer onto the titanium the baked on cobalt oxide wins the conductivity contest .
Strange things can happen going from one semiconductor to another , so it is unknown what the additional interfaces with other metal oxides may do ,
and cobalt loves to form an assortment of mixed spinels , even having
three or four different oxides .....and lead and tin and bismuth are included in that group . But probably just keeping to the cobalt oxides should
produce a serviceable anode . I can't find one single definitive
reference though , that describes any perchlorate production experiment using the cobalt oxides as
a working anode surface . So don't throw away the
HCl solution of 95/5 wire solder just yet . The cobalt
nitrate baked onto the outside of it could also be a working anode surface . Nothing like a layer cake for
solving transition problems .
Baked on manganese dioxide should go onto the cobalt oxide
with no problems . And the manganese dioxide has been tested in conjunction with cobalt doping , as useful for perchlorate production ( US4072586 )
although the layering was different ....I'll have to go back and review it , but at first thought it seems like it would work fine , and I was
thinking about that combination originally when cobalt first came up .
[Edited on 26-6-2007 by Rosco Bodine]
|
|
|
12AX7
Post Harlot
Posts: 4803
Registered: 8-3-2005
Location: oscillating
Member Is Offline
Mood: informative
|
|
The solution is more or less purple today. Chromium acetate complex?
Have cleaned off the anode, which seems to be well pitted at the bottom, except for some areas which looked kind of brown.
I cooked it hotter this time -- about 1600°F / 850°C, giving a dark gray color with some iridescence. If I were to guess at the XRD pattern, I'd
put my money on something like FeCr2O4.
Any bets on what the mixed solution will do? At worst, iron will oxidize to ferric, chromic to chromate, and possibly nickel peroxide will form
(maybe doping the PbO2, if any forms). Nickel and lead are similar in reduction potential (to metal) so are likely to plate out as has been going.
If I have 2V across 20 ohms, I'll have 0.1A, or for roughly 3 in^2, around 6mA/cm^2. Still high? Meh, I don't care about finish just yet, I have to
find out if the anode even remains stable.
Tim
|
|
|
dann2
International Hazard
Posts: 1523
Registered: 31-1-2007
Member Is Offline
Mood: No Mood
|
|
| Quote: | Originally posted by Rosco Bodine
Strange things can happen going from one semiconductor to another , so it is unknown what the additional interfaces with other metal oxides may do ,
and cobalt loves to form an assortment of mixed spinels , even having
three or four different oxides .....and lead and tin and bismuth are included in that group . But probably just keeping to the cobalt oxides should
produce a serviceable anode . I can't find one single definitive
reference though , that describes any perchlorate production experiment using the cobalt oxides as
a working anode surface . [Edited on 26-6-2007 by Rosco Bodine] |
Some info. here (at bottom)
http://www.geocities.com/CapeCanaveral/Campus/5361/chlorate/...
uses Indium Nitrate an an interfacial coating between Co+other stuff and the Ti substrate.
I have seen a ref. to using Co to make Perchlorate, cannot remember where. Will look up.
Dann2
|
|
|
jpsmith123
National Hazard
Posts: 764
Registered: 24-6-2005
Member Is Offline
Mood: No Mood
|
|
Camping Gear As A Source Of Titanium
This place has 7" titanium tent pegs for $3.56, and all kinds of titanium cups, plates, cookware, etc., made by "Snow Peak".
My guess is that it is probably not CP Ti but an alloy.
http://www.backcountry.com/
|
|
|
Rosco Bodine
Banned
Posts: 6370
Registered: 29-9-2004
Member Is Offline
Mood: analytical
|
|
great minds think alike
@dann2
Those very patents were being read today as part of my
stroll along cobalt avenue to the intersection with titanium boulevard .
Some flashy ladies were there sporting zirconium and indium jewelry asking me if I wanted to party ,
said ruthenium might even be next and I said no thanks ,
I'll keep looking Maybe I'll try sitting at the intersection myself ,
playing a harmonica and holding a tin cup between my feet . Then I got to reading a later Dow Chemical patent
by the same inventors , US4428805 (attached) . Column 9 ,
Example 3 , Table 2 was especially interesting along the
top line where increasing current clearly showed the substituted Cobalt Zinc spinel Co2ZnO4 ahead , and the straight Cobalt Oxide Co3O4 pulling ahead
of the exotics if the same trend increases to the triple or quadruple that current density where a perchlorate cell would be running . The exotics
shine at the lower current density .....but crank up the amps and they fall behind the cheaper and less complicated materials . Bye bye ruthenium ,
ect.
Actually a couple of patents listed on your further references page provide similar examples of Cobalt Nitrate alone or
in combination with Zinc Nitrate being used to provide a superior conductive and non-passivation layer when applied directly to a titanium substrate
and baked .
http://www.geocities.com/CapeCanaveral/Campus/5361/chlorate/...
US4061549 and US4142005 on your page have examples that are included in the later patent US4428805 mentioned above and attached below . In the
comparative example
on page 6 of US4061549 , a commerical titanium anode having a ruthenium doped titanium substrate tested slightly
higher voltage requirement than a Zinc Cobalt spinel directly deposited on titanium . The superiority of the spinel becomes even clearer from the
current density chart in the later patent attached below .
[Edited on 27-6-2007 by Rosco Bodine]
Attachment: US4428805 Baked Cobalt Spinel Anode Coatings on Titanium Substrates.pdf (202kB)
This file has been downloaded 977 times
|
|
|
garage chemist
chemical wizard
Posts: 1803
Registered: 16-8-2004
Location: Germany
Member Is Offline
Mood: No Mood
|
|
My grade 1 titanium strips have arrived, though I have yet to buy a quartz tube for my tube furnace and make TiCl4 in order to be able to properly
coat them.
Also, the preparation of titanium tetrabutoxide from TiCl4 is not as straightforward as one may think. The reaction between TiCl4 and 1-butanol only
takes place in the presence of a base which binds the HCl. Ammonia is used: TiCl4 is dissolved in a large excess of dry butanol and dry ammonia gas is
added. The NH4Cl which precipitates is filtered and the filtrate distilled in order to separate the Ti(OBu)4 from the excess butanol.
The problem is that no excess of ammonia must be used, as more than the theoretical amount of it will destroy the ester as fast as it forms it. So I
will probably have to weigh the reaction mix in order to find out when the addition of ammonia must be stopped.
Or I'll weigh the ammonia as NH4Cl and liberate it with NaOH, in order to only generate the theoretical amount in the first place.
And of course theres the RuCl3 problem, which will be more difficult to solve than the Ti(OBu)4 problem.
So its all going to take a lot of time.
|
|
|
Rosco Bodine
Banned
Posts: 6370
Registered: 29-9-2004
Member Is Offline
Mood: analytical
|
|
Hmmmm..... No problem , because you don't need all that .
Clean and acid etch / cathodize - hydride your titanium .
Paint with Co(NO3)2 and bake at ~360C for 10 minutes .
Repeat twice .
Then apply whatever subsequent build coats of oxides
that suit your fancy , via electrodeposition or baking
or combinations .
Or you can get about the same thing using the antimony doped tin oxides initially .
You don't need to involve separately made titanium oxides
with reducing schemes for making suboxides , nor do you need exotic or noble metals to get a non-passivating
and good conducting intermediate layer on titanium .
|
|
|
Twospoons
International Hazard
Posts: 1282
Registered: 26-7-2004
Location: Middle Earth
Member Is Offline
Mood: A trace of hope...
|
|
Given that my local pottery supplier has both cobalt oxide and carbonate, which is going to be easier to convert to the nitrate? ( I have large
amounts of nitric acid).
Rosco, my heartfelt thanks for sharing all these patent pdf's with us - I never seem to have enough time to do all the patent trawling you seem to
manage!
Helicopter: "helico" -> spiral, "pter" -> with wings
|
|
|
Eclectic
National Hazard
Posts: 899
Registered: 14-11-2004
Member Is Offline
Mood: Obsessive
|
|
The carbonate is probably more reactive.
|
|
|
Rosco Bodine
Banned
Posts: 6370
Registered: 29-9-2004
Member Is Offline
Mood: analytical
|
|
may want to get some zinc also
| Quote: | Originally posted by Twospoons
Given that my local pottery supplier has both cobalt oxide and carbonate, which is going to be easier to convert to the nitrate? ( I have large
amounts of nitric acid). |
The carbonate for sure will be easiest . It will probably go easiest if you make a thin slurry with plain water , and then
add the nitric acid by drops while stirring . If you get the drip rate just right , each drops sudden effervescence will subside
just as the next drop arrives , and it will go faster as the
mixture gets hot and more fluid . I do it that way with basic copper carbonate which is similar and it goes very smoothly
to a strong solution of the nitrate . It may heat up to b.p.
if you have a lot of it in the beaker , so a cool water bath
may help to speed the addition if it gets too exothermic and
slows down the addition too much for patience .
| Quote: |
Rosco, my heartfelt thanks for sharing all these patent pdf's with us - I never seem to have enough time to do all the patent trawling you seem to
manage! |
No problem , I have a backlog of experiments for spending way too much time researching , but then it usually saves time in the long run not to be
reinventing the wheel .
Most stuff I would do an experiment to learn , somebody else was thinking the same thing and already did it , so it saves me the time if I run across
it .
About the zinc .....that cobalt and zinc bimetal spinel looks like the one that tested best .
I have some zinc carbonate
which was precipitated from the sulfate . But I am concerned
about any sulfate impurity that may still come across into the
nitrate . I am thinking it may be good to use a barium salt
getter for the sulfate , and some further purification . I think I have some reagent zinc granules and I may just dissolve those directly in HNO3 to
save the trouble of purification .
With semiconductor chemistry like we are doing , the purity requirements on some of these compositions could be unusually stringent . I know that
certain impurities in many of the semiconductor compositions is intolerable ....and to what extent that applies here is unknown . I have a feeling
that QC is pretty rigid for a lot of these schemes to work , reagent purity , bake times , current densities ....ect.
The QC may not be as bad as clean room conditions for
microcircuits .....but it possibly is sensitive more than what
may be usual for not too exacting general hobby chemistry .
On some of this stuff it may absolutely matter that glass
containers were used , instead of plastic like polyethylene
or polypropylene or PFA , simply for whatever impurities may
leach from the glass . This is where I pull out my 2 liter
PFA beakers which have been sitting idle for too long .
That "traffic light patent" for colored lead oxides in the lead salts preparation thread is a specific case where even trace silicate can complicate a
particular semiconductor oxide formation ....for example . That same story could hold
true for these other semiconductor materials where a
very specific structure for the material is required . How
sensitive they are to process variables and impurities is a huge unknown .
That series of Dow patents involving the cobalt spinels is
the most interesting thing I have seen . I like the idea
of using the Sn - Sb oxides interface because it makes
the baking temperature less critical for the cobalt spinel
that would go over it . I think that maybe the best system
would be to use a perforated sheet titanium substrate ,
with the Sn - Sb intermediate layer , a spinel coating of
the ZnCo2O4 , and then an electrodeposited PbO2 outer layer . That would seem to be about as nearly permanent as possible for a perchlorate anode ,
as can be made without expensive exotic materials .
Relevant substrate patents are US4061549 , US4369105 , US4428805 .
[Edited on 28-6-2007 by Rosco Bodine]
|
|
|
jpsmith123
National Hazard
Posts: 764
Registered: 24-6-2005
Member Is Offline
Mood: No Mood
|
|
I wonder how pure are the chems from ceramics shops?
Somewhere online I happened upon a discussion in a newsgroup or forum somewhere regarding buying cobalt compounds from ceramic supply stores.
As I recall, one of the participants in the discussion felt that he had purchased some cobalt carbonate that was cut with something else...something
less expensive. He felt that with the high price of cobalt compounds, there was an incentive for vendors to cheat a little bit.
Anyway, according to the patent Rosco found, the acetate salt supposedly works, too, so maybe you could save your nitric acid and mix the carbonate up
with some distilled vinegar instead?
| Quote: | Originally posted by Twospoons
Given that my local pottery supplier has both cobalt oxide and carbonate, which is going to be easier to convert to the nitrate? ( I have large
amounts of nitric acid).
Rosco, my heartfelt thanks for sharing all these patent pdf's with us - I never seem to have enough time to do all the patent trawling you seem to
manage! |
|
|
|
Twospoons
International Hazard
Posts: 1282
Registered: 26-7-2004
Location: Middle Earth
Member Is Offline
Mood: A trace of hope...
|
|
Thanks, but I don't really need to save nitric. I have about 12 litres of 68%, just sitting around, not being used for anything much.
Its possible the carbonate isn't deliberately 'cut', just that the impurity is of no consequence in pottery. Cobalt is a *very* strong glaze
colorant.
Supposing purification was needed: plate out the metal, then redissolve in nitric, maybe?
Helicopter: "helico" -> spiral, "pter" -> with wings
|
|
|
not_important
International Hazard
Posts: 3873
Registered: 21-7-2006
Member Is Offline
Mood: No Mood
|
|
The carbonate is est, pottery cobalt oxide is generally the mixed II/III oxide and seems a little slow going into solution in oxidising acids.
A simple thing that can help with purity is to not use an excess of acid, but have some of the oxide/carbonate/hydroxide left. Gently boil the mix for
awhile, then let cool and filter. In some cases you want to then add enough nitric acid to have an excess, or add H2O2, and bring to a boil again,
then add enough of the carbonate or hydroxide to push it back alkaline and have some solids in suspension; this converts iron the the Fe(III) state
and then pulls it out as the hydroxide.
Plating out from solution isn't going to do too much purification. You can get some by plating from a Co metal anode and plate onto the cathode with
as low a voltage as will cause a decent plating rate. Just pulling the metal out of solution using carbon anodes tends to plate out other metals not
too different in electromotive standing.
Crystallisation is the other route, leaving a fair amount of the salt in solution. In the case of cobalt nitrate, the solubility in alcohol is high
enough that you can do a crystallisation from alcohol, then another from high purity water.
|
|
|
Rosco Bodine
Banned
Posts: 6370
Registered: 29-9-2004
Member Is Offline
Mood: analytical
|
|
Maybe purification isn't even needed . Heck at first , I think just make the nitrate solution , perhaps leaving slight amount of undissolved
carbonate as mentioned ,
give it a good boil and rapid filtering through a cotton plug in a funnel to polish the hot solution .
Then boil it down until some crystals of the trihydrate ?
Co(NO3)2 start appearing , and when the temperature
drops to ~70C , decant the liquid and repeat . Taking the trihydrate product at well above the 56C where the hexahydrate formation occurs should
clean it up pretty good as a first pass .
Then make a 50% ( or stronger ) solution in alcohol (based on the hexahydrate) , adding 3 equivalents of H2O if needed but it probably won't be needed
.
I don't have specific information , but I expect the anhydrous salt or maybe a monohydrate could likely be crystallized out readily from cooling a
saturated hot alcohol solution.....unless this is a wierd one that has an alcohol of crystallization .
Just that much manipulation is probably sufficient .
If it proves not to be good enough , then later maybe
a chemical reduction to the free metal , using vitamin C
or formaldehyde or glucose , and then redissolving the
metal in acid for another pass ought to do it . But it probably wouldn't come to that .
|
|
|
Rosco Bodine
Banned
Posts: 6370
Registered: 29-9-2004
Member Is Offline
Mood: analytical
|
|
cobaltous acid
While reading a pretty comprehensive article on cobalt
on the following page
http://www.1911encyclopedia.org/Cobalt
the following sentence caught my notice
| Quote: | | By suspending cobaltous hydroxide in water and adding hydrogen peroxide, a strongly acid liquid is obtained (after filtering) which probably contains
cobaltous acid, H2CoO3. |
I thought that possibly this cobaltous acid might make a good first treatment for a freshly etched and possibly hydrided titanium , as it might react
at normal temperature with the bare titanium to form a desirable interface layer ,
as a sort of sealant and primer layer , possibly improving
the adhesion and conductivity at the interface of titanium metal to any following layers of oxides , whose precursors
may be applied and then baked to form the subsequent heavier layering of oxides . This would seem applicable
especially for the bimetal spinel formed from cobalt and zinc nitrates , but would possibly also benefit the mixed tin and antimony oxides .
The cobalt hydroxide reaction with hydrogen peroxide reminded me of the peracid formation which occurs with vanadium pentoxide , and I thought perhaps
a useful
combined vanadium cobalt peracid or persalt complex , might also form under these conditions . Also the peracid of vanadium is known to form very
soluble peracid complexes with higher alcohols like tertiary butanol , and this complex
or some mixed complex with cobalt might be possible .
These might also form soluble complexes with organic peroxides which may be capable of "doping" an initial interface layer on bare titanium *in the
cold* , which would likely be evident as a colored film or haze on the metal .
This is something that was just an idea which occurred to me
and I can't find anything in searching that is related to this idea . But it seemed like a good candidate for an experiment , if only as an
alternative to or in combination
sequence with some electrodeposition scheme for a first interface layer on the bare titanium .
|
|
|
| Pages:
1
..
17
18
19
20
21
..
47 |
![[*]](images/xpblue/default_icon.gif){kind=icon}
