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[*] posted on 10-6-2007 at 06:15


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[*] posted on 10-6-2007 at 11:32


Hello,

Regarding the Silver connections needed for massive anode. Silver Perchlorate is an explosive and therefor the Silver must be kept away from the Perchlorate cell. It think it would be prudent to keep it away from a Chlorate cell too.(same goes for Copper).
Silver will not do as an interface coating on any anodes IMHO for this reason along.

Ti is a valve metal (this has been explained by others but since I seem to like typeing..............)
The Valve Metals consist of (AFAIK) Al, W, Ti, Ta, Hf, Nb, Zr. They form oxide coating that are diffucult to penetrate under anodic conditions. Al is useless (only a few volts) W I dont know, it may be a possibility for

the Amateur as it is easily available as a rod in welding shops. It's oxide may not dissolve into our Doped Tin Oxide coating though. Ti is good Ta, Hf and Nb have oxide coatings that are more anodic protective that Ti. Their oxides may not dissolve in out Doped Tin oxide though. Zr.... is it a valve metal??

The DTO is not an attempt to make diodes (zener or otherwise) but simply a way to stop Ti Oxide (non conductive) from forming on the Ti in the presence of Lead Dioxide. It is a cheap alternative for a flash coating
of Pt.

Ta is expensive but is crops up on ebay fairly regularly. The other are too, shall we say, 'exotic'.
Ta is fairly easy to drill and work as I have a piece.
Ti (Grade one) is easy to drill and debur. It is quite soft.

I got some Ti today. It is three mm thick which is a bit thick. I presume

I can make it thinner simply by putting into NaCl and passing current (high enough Voltage).... I might even make some Chlorate as a biproduct, eh.


If the (Per)Chlorate solution has the ability to creep between the Lead Dioxide and the doped Tin Oxide (or between the DTO and the Ti) then the whole idea of 'non-professional' Lead Dioxide coating on Ti will not work I guess as Rosco said. But it will self heal (self seal) at least.

From Industrial Electrochemical Processes (book) page 550 is a graph of Anodic breakdown voltage of Ti (C.P. (Commercialy pure)) as a percentage of the breakdown voltage at 20C in brine solution.

At 20C it is 100% (obviously)
40C 85%
60C 70%
80C 55%
100C 45%

Would this be similar(ish) for Chlorate solutions. I presume it is fair to assume that Ti WILL be self healing in Chlorate.

The value of Ti at 20C in brine is approx. 15 volts, way above anything we will be throwing at it. It increases as current density goes up.
Ta is way above this.

From Electrodes of Conductive Metallic Oxides page 637.

I will put a piece of Ti into a Chlorate/Perchlorate solution, rise the

Voltage and see where it breaks down. I would be better doing it this way than going the theory route .
Ti is used for DSA anodes, where it is self healing.



Regarding hanging a porous packet of Lead Compound in the plating tank it would probably help. The carbonates will cause bubbles. If you could get the hydroxide. Litharge can be hard to get to dissolve but may be the best.
I think you are better off thinking in terms of free Nitric acid in the solution that in terms of pH. The pH is above two, say, it will vary easily. If you simply try to keep the free Nitric acid at a level of about 3 or 4 grams per liter of solution (low pH) this may be the best way to think/go about it. Will a pH meter do this? measure real low pH accurately?
I wonder would a hydrometer in the solution measure the density of Lead Nitrate and give you an idea of how much to dribble in. If dribbling in Lead Carbonate or basic carbonate or hydroxide you are better off making a slurry of theses compounds as when dry they float on the surface making
one hell of a mess.

With the massive anode I notice that is is suggested that it be grown on the INSIDE of a cylinder. I think this suits the internal stress built up on the anode better. If grown on a flat or worse, on the outside of the cylinder they are more prown to failure.
(Can't remember where I read that, it is difficult to remember all sources).

From Chemical Engineering 1965 July 19 page 82:
Below a picture of a large stack of GSLD Anodes:
_____________________________________________
Before Pacific Engineering could make a breadthrough in electrochemical processing, it had to overcome the defects in Lead Dioxide anodes that had plagued previous researchers. These included nonuniform and nonadherent coatings that were too course and porous, short electrode life due to corrosion and inability to stand up to typical commercial handling.
bla bla,
Pacific makes its anodes by first machining and shaping the graphite to very exact specifications. After the graphite is soaked in water and the bare anodes are placed in plating cells through which Lead Nitrate electrolyte circulates. A small amount of nitric acid in the electrolyte improves coverage.
During the plating the current denisty is varied according to a very exact specification. Higher current densities are supplied at the beginning then amperage is reduced. Seven hour depositon time.
_________________________________________________________

If the professionals were plagued with problems, what about the rest of us.
The GSLD Anode are not simple either. I would think Pacific
Engineering had more time and cash than myself..... here I go again..............:-)
Perhaps the Ti substrate will prove to be of similar fickle nature.


I'm SFTMFTATSFK. (Spending Far Too Much Fucking Time At This Stupid Fucking Keyboard :-))

If massive anode were so simple lots of us would have a massive anode in our Chlorate cells when the substrate was eaten away.
Fineto

I wonder what the big Perchlorate manufacturers are using nowadays for Perchlorate manufacture?

Short, terse answers ONLY, thank you. PC incorrect 'eyes rolling icon' here.

Dann2
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[*] posted on 10-6-2007 at 11:59


@ Alan

Quote:
Originally posted by alancj
I was thinking that the surest way to control pH (and therefore lead ion concentration) would be to use a pH probe in the plating tank, and interface that with a microcontroller to drive a small agar to deliver salts to an addition tank, which is circulated with the plating tank. (oddly enough, I live a half mile away from a company that manufactures agars for pellet stoves!) Maybe just knowing the plating deposition rate one could do it without automatic feedback, and skip the probe. I think that is what you'd have to do with an acidic plating bath at least.

Great minds think alike ! I have been wondering if there is a
pH color indicator which would endure the conditions to provide a visual monitoring of the pH of the electrolyte .
The idea of using a pH probe and an automatic controller like is used for the pH control in hydroponics also has been in my mind . But instead of an auger , you just output the controller to a small motor driven globe valve which increases
or decreases the proportion of diverted flow from your circulator pump to the "percolator funnel" in order to provide
a variable pH up function , while the ongoing electrolysis provides a steady pH down function that is being balanced at any desired pH which is programmed as a setpoint for the controller regulator . So long as the volume and temperature of the electrolyte is held pretty constant , not allowed evaporation loss for example , a simple bath conductivity sensor reading might be a good indicator
of pH without having to use an actual pH probe . Two lead plates with a low regulated DC voltage across them like 0.7 volts and a current monitor to babysit , might be a workable
pH monitor for input to an op amp regulator setup .
Quote:

For a neutral one I think a percolation funnel would be fine, like Rosco mentioned. IMO it would be pretty hit or miss trying to get a lead compound with the right properties so as to dissolve at the exact rate you want at the exact pH etc., in anything but a neutral plating bath. -Alan

Yeah , the choice of lead basic salt used would automatically
choose the equilibrium pH for you , and concentration of the
bath would always be near saturation , unless you were manually manipulating it . The scheme for a percolation funnel can actually be run in reverse as a fluidized bed ,
like what a sand filter would be doing when being flushed
for cleaning . I didn't want to complicate things by going
into that , but it is really the best way to use that sort of technique as it stirs and churns the neutralizing particles
in suspension , greatly increasing the efficiency of the
neutralizer .

@ hashashan

Quote:
Originally posted by hashashan
There goes an interesting question :
If we do hang something like a tea bag of lead carbonate(or any other lead compund that will react with HNO3) what will happen? will the trace amounts of HNO3 forming will react immediately with the lead compund hence making a neutral bath. Or because of no movement in the tank the only reaction will be caused by drifting of the solutions and making quite stable acidic PH?


What I was saying there is it would be better than nothing
to have a teabag sort of neutralizer in a one tank simplified setup , if any sort of pH control of the crudest sort is acceptable . But really a pumped system is the best way to go , and you can control the rate of the neutralizing somewhat simply by diverting more or less of the recirculated
flow to or away from going through the neutralizer .

@dann2

The method of US4064035 supposedly eliminates that need for a curved surface substrate which matches the natural
curvature of the deposit of PbO2 . US2859166 uses a
shielding method which also eliminates that curling effect .



[Edited on 10-6-2007 by Rosco Bodine]
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[*] posted on 10-6-2007 at 14:01


Quote:
Originally posted by dann2
[...]
I wonder what the big Perchlorate manufacturers are using nowadays for Perchlorate manufacture?
[...]


The only things I've ever seen offered for sale for perchlorate manufacture are: 1) Platinum over titanium, and 2) PbO2 over titanium.

Platinized titanium mesh anode
Platinum plated titanium plate anode
Platinum cladded titanium anode
Lead dioxide coated titanium mesh anode
Lead dioxide coated titanium box anode
Lead dioxide coated single stem titanium box anode
Lead dioxide coated double stem titanium box anode

http://www.titanindia.com/potassium%20perchlorate%20cell%20a...

BTW Dann2, have you ever tried the in situ oxidation of a lead plate? IOW, mount a piece of lead in a cell, add a dilute H2SO4 solution, anodize to build up a thin layer of PbO2, then without touching the anode, drain the H2SO4, fill with NaClO3 solution, and electrolyze.

I'm thinking that if the electrodes in the original Plante cell were made that way, maybe they're rugged enough to work at least a few times in a ClO4 cell.
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[*] posted on 10-6-2007 at 14:50


Hello,

Never tried the Lead Plate in H2SO4 idea.

Will the deposit be non porous and adherent is the question. It would not be a very expensive thing to try out.
What conc. of Sulphuric would you recommend.

There was a process mentioned on this board for making Chlorate (and Perchlorat??) using Lead Bars. It was some Government sponsored project from years ago. I never seen or read it. Do you know where it is. Perhaps it might point the direction of where/what you need to do with a Lead Anode. It would be a toxic product IMHO. Handling(dilute) soluble Lead Compounds in the product.

Regarding the Valve metals..........

I connected my selection (!) of Valve metals to a power supply (DC). The electrolyte consisted mainly of Na Chlorate, some Perchlorate and a few % Chloride.

Ti was struggling at 23 volts and broke down at about 25/26 volts. The Ti is Grade one.

Ta was OK all the way up to 45 volts, the max. of my power supply. The Ta is pure.

W was OK all the way up to 45 volts, which was surprising. I tried two pieces of W as I had suspected that the flat sheet I had purchased on Ebay (some time ago) was not W. So I also tried a TIG welding electrode which is W. It too was OK all the way up to 45 volts.
This is surprising. The flat sheet is pure, I don't know about the TIG welding piece but I think it is pure sintered W.

I also tried Al. It was pure Al (Analythical reagent granuals). I got the biggest piece I could get. It was hopeless with no 'Valve' quality at all. I seen Al listed as a Valve metal once.

W TIG welding rods are available at all welding shops for a dollar or two. I wonder would they do instead to Ti. Perhaps the DTO (Doped Tin Oxide) would not dissolve with/into the W Oxide.
I guess it would be wise to keep with Ti for the moment.

When the metals were put into the electrolyte a surge of current flowed which then dwindled to zero. Got some pretty colours too.

I am in the process of calibrating my thermocouple thermometer. A thermocouple wire + voltmeter.
Do any of you guys know of an alloy that will melt at 450 to 480C (approx) This is the temp. for baking the DTO on Ti. I do not think it is wise to go above 500C because of the transition of Ti oxide. It undergoes a volume change.

I have already melted Lead and Zinc. Perhaps theses two data points will do me.
Too stingy to purchase a proper thermometer.
500C is described as 'grey' heat when viewed from the point of view of colour.

It is a high tech oven. Floor tiles in a coffin shape about 6 by 6 by 30 cm held together my copper wire and surrounded by perlite (volcanic rock from a garden shop) all in a tin box.

Heater is a Nichrome spiral connected to a variac.

I will be using Stannous Chloride and Ammonium Molybdnate.
Most of the patents call for Stannic Chloride + Antimony Chloride. But a patent on my site give a list of compounds and theses were included.
Will Stannous Chloride do, do ya think??

It is available on ebay + the Ammonium Moly.

DANN2
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[*] posted on 10-6-2007 at 15:07


MadHatter

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posted on at 01:36 AM

KClO4



gilbert pinkston, I've already made plenty of potassium perchlorate without
problems. As for indigo carmine, I have enough of that for a long time. Found
50 grams on eBay for $25. Not bad considering the higher prices I've seen
elsewhere on the net. My last batch of KClO4 was about 8 LBS. Very nice,
flat rhombic crystals in contrast to the KClO3's cactus needles which are
produced 1st during the electrolysis. BTW, I should have mentioned in 1 of
the earlier posts that the indigo carmine test can detect chlorates down
to 1 ppm. The test is sensitive enough to ensure that there shouldn't be
any problems when making NH4ClO4.
--------------------------------------------------------------------------------------------

this is from an earlier post MadHatter seems to have made perchlorate at will what is all this talk why not use his method?
by the way what was his method?
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[*] posted on 10-6-2007 at 15:34


A Schottky diode structure is what is being implemented
with the valve metal and semiconductor oxide laminate .

http://en.wikipedia.org/wiki/Schottky_diode

It may be that there are electrolytic methods involving different valve metal combinations which are detailed in
semiconductor literature , as this would be likely to have been the subject of more research for the electronics applications , than for "off label" use as anodes .
Various dopants and methods for lowering the reverse breakdown voltage to essentially have an ohmic semiconductor layer over the metal substrate may already be extensively described in the literature where
the various combinations were (hopefully) the source of experiments in rectifier design . Whatever dopants
were the most counterproductive for the reverse breakdown voltage parameter of the diode are precisely
the dopants which would be of interest for the anode
application .

[Edited on 18-6-2007 by Rosco Bodine]
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[*] posted on 10-6-2007 at 15:46
In Situ PbO2 coating on Pb


The following procedure is from a page dealing with chrome plating.

################################

ANODES

These are made of lead strips. Various sources can be found, but the material I use is about 1/8" (3.175 mm) thick cut or formed into the required shapes from a 4" (101.6 mm) waste pipe section available from plumbing/hardware stores. Joiner sections can be bought about 8" (203.2 mm) long.

Lead is attacked by chromic acid and an insulating layer of lead chromate (yellow in colour) will be formed if the anodes are not first treated. This lead chromate interferes with the plating current flow, but is easily avoided by transforming the working surface of our anodes into lead peroxide. The oxide prevents the formation of lead chromate, whilst allowing the passage of our plating current.

4.1 PEROXIDING THE ANODES

NOTE: For current density required for this treatment, the current is 5A/sq ft. (0. 035A/sq. in., or 0.55A/DM2) of total wetted anode areas.

Make up a 5% solution of sulphuric acid in water
Clean by scraping the lead anodes
Connect two of these lead anodes to the DC power supply, one positive, one negative
Adjust the current density to 5 A and maintain this for 15 minutes
Reverse the polarity of the DC supply and maintain 5 A for 15 minutes
Finally, reverse the polarity of the DC supply one more time and maintain 5 A for another 20 minutes

A dark brown coating on the anodes will indicate the presence of our protective layer of lead peroxide. Dry the prepared anodes and put them aside, ready for use. This process will be repeated on any anodes which tend to develop yellow spots during use (because of the lack of the lead peroxide coating).

http://freepages.pavilion.net/users/nickfull/chrome.htm
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[*] posted on 11-6-2007 at 14:21
PbO2 Plating


Jp, where did you find this ? I'll have to try this out. If this works more easily than the
lead nitrate plating bath then our perchlorate production problems may be solved.
I've had bad luck plating carbon/graphite rods with PbO2 because they're extremely
fragile.




From opening of NCIS New Orleans - It goes a BOOM ! BOOM ! BOOM ! MUHAHAHAHAHAHAHA !
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[*] posted on 11-6-2007 at 15:17


Hello MadHatter,

I came across that article while I was trying to find out how the original lead acid cells were made by Gaston Plante.
I'm still trying to find that information.

I did find the following references...now if only someone could get the full text papers.

http://www.osti.gov/energycitations/product.biblio.jsp?query...

http://www.osti.gov/energycitations/product.biblio.jsp?query...
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[*] posted on 11-6-2007 at 22:11


But isnt that in the beta form? we need the alpha.
IIRC the PbO2 on the lead will be brown and fluffy, and it will just flake off as soon as we start electrolizing the NaCl solution.
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[*] posted on 12-6-2007 at 02:09


I think you have it backwards. Beta is the form we want for anodes.
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[*] posted on 12-6-2007 at 02:23


As I understand it, it mostly beta when formed in this manner.

In any case, it seems to me the PbO2 coating must be somewhat robust, or it wouldn't have worked in Plante's cell, nor in the chrome plating application mentioned here.

Maybe someone can give it a quick try and report back?
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[*] posted on 12-6-2007 at 02:34


ok so i meant the other way around. That doesnt really matter, its still a different form. And such a form that is made wit this method i no good for us.
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[*] posted on 12-6-2007 at 03:17


How do you know it won't work? Or have you tried it or some similar process? You may be right, I don't know. Understand, all I'm talking about is finding a quick and dirty way to make a few lbs of perchlorate...I'm not talking about making some rugged, long lasting, state-of-the-art anode.
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[*] posted on 12-6-2007 at 03:34


i didnt try it. I just dont believe itll work because there is no way that the PbO2 remain on the anode.
I would be glad to know if anyone tried that
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[*] posted on 12-6-2007 at 10:06


Quote:
Originally posted by jpsmith123
As I understand it, it mostly beta when formed in this manner.

In any case, it seems to me the PbO2 coating must be somewhat robust, or it wouldn't have worked in Plante's cell, nor in the chrome plating application mentioned here.

Maybe someone can give it a quick try and report back?


What is the Plante's cell. I USFSF but could find nothing.

Regarding Alpha and Beta.
The Beta seems to be the one industry goes for. It is better wearing than Alpha. Alpha seems to stick better to things so that is why it will be recommended as a first coat.
Some patents/articals use both claiming both together give less stress------> less crcking.
The Beta has a higher overvoltage for Oxygen giving more efficient production but nothing that would be any great advantage to us.
I'll take either if they work.!

Dann2
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[*] posted on 12-6-2007 at 13:42


Well, if it was as fragile as you suggest, then I find it hard to believe that it was used in the original lead-acid cell. Don't forget, we're not talking about about a thick coating here.

BTW, as I understand it, alpha PbO2 is what you'd like to form first, and then beta over it. So maybe begin the process with a relatively high pH and then lower it? I don't know...it seems like it would be worth experimenting with this a little bit.

Quote:
Originally posted by hashashan
i didnt try it. I just dont believe itll work because there is no way that the PbO2 remain on the anode.
I would be glad to know if anyone tried that
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[*] posted on 12-6-2007 at 23:44


Hi, I started another batch of perch with my old PbO2 anodes. Now i know that the curr.density for those should be 150-400 mA/cm^2 but are there any limitations on the cathodes? (i use graphite cathodes)
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[*] posted on 13-6-2007 at 00:45


Quote:
Originally posted by jpsmith123
BTW, as I understand it, alpha PbO2 is what you'd like to form first, and then beta over it. So maybe begin the process with a relatively high pH and then lower it? I don't know...it seems like it would be worth experimenting with this a little bit.


Something worth experimenting with would be a combined
PbO2 plating bath containing a mixture of lead acetate and lead nitrate , and operated at a very mildly acidic pH , perhaps pH 5.3 . The patent US4064035 teaches the
application of sequential layers of alpha and then beta lead
dioxide , but the process interrupts the plating between layers which uses different plating baths for each allotrope ,
rinsing off the alkaline residue from the alpha plating bath ,
and transferring the electrode to a nitrate bath for the
resumed plating to deposit the beta layer .....and so on ,
the interruption of plating likely producing a boundary layer
where a delamination could occur at the interface beween the differing strata .

If you look at the plating conditions in the Union Carbide patent US3033908 (attached) , it describes a plating of alpha PbO2 from a slightly acidic lead acetate bath at about a 20% electrolyte concentration and a current density of 35-50A sq. ft . And if you look at the JES Bromate Cell article
http://www.sciencemadness.org/talk/viewthread.php?action=att...
where the anode preparation is described , at a similar pH and concentration of electrolyte and current density which is
identical , except that lead nitrate is used to deposit the
beta PbO2 ......it is reasonable to conclude that likely
a coelectrodeposition of alpha and beta PbO2 is possible from a mixed lead acetate and lead nitrate electrolyte .
Hopefully the mixed forms of PbO2 deposited would form an internally stress relieved deposit which would plate out evenly without any tendency to curling , as the product of
an uninterrupted plating which would have greater mechanical strength and stability . I can find nothing about this in the literature but it would seem to be a highly logical next experiment with regards to the massive PbO2 anode .
This technique if it works might have value for improving heavy coatings of PbO2 which are applied to any sort of substrate also .

The only complication which I have anticipated is that the potential may be slightly different for the plating out of one form or the other , and it may require a waveform of varying DC to accomplish a smooth mixture ....something like a rectified AC of an appropriate voltage without regulation and filtering could work better for this than a regulated DC supply .

[Edited on 13-6-2007 by Rosco Bodine]

Attachment: US3033908 alpha LEAD_DIOXIDE from lead acetate and sodium nitrate plating bath.pdf (136kB)
This file has been downloaded 826 times

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[*] posted on 13-6-2007 at 14:52
Cathode current density


Quote:
Originally posted by hashashan
Hi, I started another batch of perch with my old PbO2 anodes. Now i know that the curr.density for those should be 150-400 mA/cm^2 but are there any limitations on the cathodes? (i use graphite cathodes)


Hello Hashashan,

I am not aware of any magical number for current density on Cathodes.
Once the figure is sensible, with a cathode each side of the anode and of similar size to keep current distribution on the Anode fairly even, it will be OK.

Dann2
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[*] posted on 14-6-2007 at 13:11
Etching Ti with Oxalic acid.


Hello,

When etching a Ti strip I added 60 grams Oxalic acid to 700 ml water. This etched the first strip of Ti OK. The solution turned an orange colour.
When I reheated the solution the next day it turned clear. I added another strip of Ti but it would not etch. I added a further 60 grams Oxalic acid and it still would not etch the Ti. (similar Ti as before)
Anyone know why??
The solution is at 80 to 90C.

Dann2
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[*] posted on 14-6-2007 at 13:14
Stannous Chloride + Ammonium Molybdnate


Hello,

Got around to trying some Doped Tin Oxide on Ti. The procedure I followed is similar to Pat. No. 3940323.
_______________________________


EXAMPLE 1

A strip of titanium plate is prepared by immersion in hot oxalic acid for several hours to etch the surface, then washed and dried. A solution of 2.2 parts of SnCl4 5H2 O and 0.2 parts of (NH4)2 MoO4 in 5 parts of water is brushed on to the cleaned titanium surface. The coating is dried by heating at 100.degree.C for about 2 minutes than heated in an oven with a forced flow of air at 400.degree.C for about 5 minutes to convert the coating substantially to the oxide form. The process is repeated three times with a final heating in air at 400.degree.C for 30 minutes
_______________________________________
The above patent is for a DSA but I am just using the DTO part of the Patent. Then going to plate Lead Dioxide.

I used Stannous Chloride (SnCl2) instead of Stannic Chloride as above.
The patent names Stannous Chloride as a compound you could use.
When I mixed the Stannous Chloride with the Ammonium Molybdnate I get a dark green precipitate. I ended up painting on a suspension as opposed to a solution.
What would you expext to get when you add Stannous Chloride to Ammonium Molybdnate? Does a dark green ppt make sence does anyone know.
What ions do you get when you dissolve Ammonium Molybdnate.
I am also not 100% sure of the purity of the chemicals.

Cheers,
Dann2
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12AX7
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[*] posted on 14-6-2007 at 16:20


Molybdate(VI) reduced by Sn(II)?



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Xenoid
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[*] posted on 14-6-2007 at 20:39
In Situ PbO2 plating


Greetings all!

I just had a go at the in situ PbO2 plating, with little success!

1mm thick Pb sheet was used to make electrodes 11cm by 6cm. The plating was carried out as described in the above procedure; 5% H2SO4 and current of 5.5 mA/cm2
I added an extra strip/coat step and extended the final coat time to twice that suggested.

I used some of my residual chlorate/chloride mother liquor and a Ti cathode to test the PbO2 coated anode. As soon as the current (1-3 A) was turned on, I was greeted with a myriad of white PbCl2 spots on the anode which grew larger and more voluminous with time!

I'll try stripping it again and give it a really thick coat, but I'm not very optimistic!

Regards, Xenoid
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