WSM Posted April 6, 2015 Posted April 6, 2015 I've got two small cells prepared for testing perchlorate anodes; one for lead dioxide and the other for platinized titanium. The electrolyte prepares relatively easily, as one would expect from a sodium salt, to 600g/Liter. I used an electric stirrer with a Teflon coated stir bar. I have one small DC power supply with constant current capability, so I'll run the cells one at a time. I've already tested the sodium chlorate electrolyte solution for perchlorate with methylene blue solution and it came up negative, as would be expected from reagent grade material. A positive test after running the cells will be a qualitative affirmation of perchlorate production. The last steps I need to do before my tests is get the meters ready. I plan to monitor voltage, amperage and temperature with digital display meters. The next step... perchlorate production! WSM
WSM Posted April 6, 2015 Posted April 6, 2015 Yes, I mentioned it completely separately.The good thing with Barium perchlorate is, that BaSO4 is insoluble and so i can make Ap with Ammonium sulfate and Ba(ClO4)2 and don't have a Sodium contamination like in the route with NaClO4 Corrosion of Platinum would also be the problem why I would like to get chloride free chlorate. I suppose you could generate sodium perchlorate and make perchloric acid from that. This would be another way to avoid sodium contamination in your AP or KP (a bit more hazardous, though). I like your thinking. WSM
pyrojig Posted April 7, 2015 Posted April 7, 2015 That line of thinking would be useful for the production of A-perch.(Making perchloric acid) It seems that you could do it with Na- perch( double exchange) , but there would be a strong chance that some Na would be left in the finished salt. What would be the preferred acid to do the exchange with ? Glad to see that your doing a test on both Platinum and Lead Dioxide . It will be nice to see what potentials and idiosyncrasy's come from ea. electrodes.It will be nice to see how this all transitions into the continuous sys . later . What a adventure !!!
Titanium Posted April 7, 2015 Posted April 7, 2015 But how can I get the Sodium contamination out of the perchloric acid? Destillation wouldn't be very Safe to do I think.
WSM Posted April 7, 2015 Posted April 7, 2015 That line of thinking would be useful for the production of A-perch.(Making perchloric acid) It seems that you could do it with Na- perch( double exchange) , but there would be a strong chance that some Na would be left in the finished salt. What would be the preferred acid to do the exchange with ?Glad to see that your doing a test on both Platinum and Lead Dioxide . It will be nice to see what potentials and idiosyncrasy's come from ea. electrodes.It will be nice to see how this all transitions into the continuous sys . later . What a adventure !!! Typically, anhydrous sulfuric acid. True. The best part is, I believe it can be done as a working table-top model (miniature of the industrial methods). WSM
WSM Posted April 7, 2015 Posted April 7, 2015 (edited) But how can I get the Sodium contamination out of the perchloric acid? Destillation wouldn't be very Safe to do I think. This will require much more research to ferret out the details, but the first method that comes to mind is distillation. Mixing concentrated sodium perchlorate (or even dry potassium perchlorate) with sulfuric acid and distilling perchloric acid from the mixture. H2SO4 + 2KClO4 --> HClO4 + 2KSO4 A proper laboratory setup would be advised, with all the neccessary safety precautions in place. Complete control of all the parameters would minimize the hazards involved. This is not a trivial endeavor. It's possible, if not advisable... WSM Edited April 8, 2015 by WSM
Titanium Posted April 7, 2015 Posted April 7, 2015 Yes, that is the problem, I don't have the equipment to perform a vacuum destilation for perchloric acid and without proper equipment it's not safe, especially in point of explosion hazard Maybe if I take the double replacement route with NaClO4 and a Ammonium salt I can get rid of the sodium by many recristalisation circles, I must try out
schroedinger Posted April 7, 2015 Posted April 7, 2015 Go for the double replacement method, it is the only way that is safe.Distillation of perchloric acid isn't worth the hassle. An other idia i have, but I'm not sure if it would work.Maybe if you take the sodium perchlorate, dissolve it and combine it the solution with a solution of oxalic acid. Sodium oxlate is close to insoluble and if you use two solutions the acid would be quite diluted , use about 0.1-0.5 % exes of oxalic acid.Imeaditly submerge the cake in a solution of ammonia carbonate to remove all of the free acid.Now filter of the precipate through glass wool and add barium carbonate until no precipate is formed to remove the excess oxalic acid. Now add ammonia carbonate or hydroxide to precipate the AP. Maybe it is worth a test, but I do not know if this route will work or not. Also limit the perchloric acid content to a max of 25% should be a good idea. Watch out perchloric acid is no joke and I'm not sure what it can do to the organic oxalate.
Titanium Posted April 12, 2015 Posted April 12, 2015 Ok thank you, I'll try that as soon as I have some NaClO4
schroedinger Posted April 12, 2015 Posted April 12, 2015 For neutralizing the cake every base will be of not just ammonia carbonate.Let us now if it works or not.
WSM Posted April 12, 2015 Posted April 12, 2015 Ok thank you, I'll try that as soon as I have some NaClO4 Hopefully, I'll have some sodium perchlorate solution soon. The perchlorate cells (one each for platinum and LD anodes) are ready, the sodium chlorate solution is made, the meters are mounted and enclosed in plastic project boxes and all I'm lacking is a decent place to set it all up. I prefer to work outdoors but need a shelter for the system and especially the electronic and electric components. Things are coming together, but it's slow going. I hope by this time next week, I'll be reporting on my experiences. We'll see... WSM
WSM Posted April 12, 2015 Posted April 12, 2015 (edited) Since "a picture is worth a thousand words", in the interest of clarity let me show and then describe the LD cell electrodes: In the Pyrex "battery jar" (about 6" diameter by 12" tall [or roughly 150mm diameter by 300mm tall]) can be seen the electrodes. The cathodes are CP titanium sheet metal. The anode is a Chinese made titanium mesh covered with lead dioxide. To protect the anode and prevent electrical shorting of the electrodes, I've slit some black Viton rubber tubing and covered the edges of the anode. If viewed carefully, some pieces of clear Teflon tubing can be seen which is used as spacers between the anode and cathodes. The electrodes are held tight in this arrangement by tension between the components and shouldn't have any electrical problems. I've replaced the titanium strap on the anode with CP titanium tubing which is filled with a heavy solid copper wire and lead-free solder (to increase conductivity and reduce heating of the leads). WSM Edited April 12, 2015 by WSM
pyrojig Posted April 13, 2015 Posted April 13, 2015 AH, very nice ... Just one Q./Concern. Is there way to secure the rubber viton from falling off when the hydrogen lift happens? I would assume that they may "slip off" when the gas bubbles form. Is there a way to retain/ secure them to the electrode .?
WSM Posted April 13, 2015 Posted April 13, 2015 AH, very nice ... Just one Q./Concern. Is there way to secure the rubber viton from falling off when the hydrogen lift happens? I would assume that they may "slip off" when the gas bubbles form. Is there a way to retain/ secure them to the electrode .? I don't think there'll be a problem, but we'll see when I run it. The hydrogen lift is primarily coming off the cathodes and the Viton edge protectors are on the anode. Also the titanium straps between the cathode plates are close enough to keep things in place (which is another reason I decided to use Viton as an electrical insulating layer, besides being physical protection for the LD edges on the anode). WSM
pyrojig Posted April 13, 2015 Posted April 13, 2015 WSM, thank you for the clarification and correction . You are right about the cathodes producing gas. Due to the close variance of the electrodes , you expressed a very good point , that the tubing should stay on . ( very clever and creative way to approach protecting these tight tolerances .) This seems like a much simpler approach than what Swede was trying to accomplish with the machined teflon.
WSM Posted April 13, 2015 Posted April 13, 2015 WSM, thank you for the clarification and correction . You are right about the cathodes producing gas. Due to the close variance of the electrodes , you expressed a very good point , that the tubing should stay on . ( very clever and creative way to approach protecting these tight tolerances .) This seems like a much simpler approach than what Swede was trying to accomplish with the machined teflon. I think Swede was on the right track and the things done since then are a natural progression from that point. As we view his blogs, it's not unlike us reviewing our own notes from before what we know today. In our past we got some things right and some things wrong, but they're all steps that got us to where we are now. Swede is an avid experimenter, and even more important, an expert documentor. He's one of the giants whose shoulders we're standing on when we make advances. In fact, the things I'm studying right now, Swede did five or six years ago! I see Swede's work with the Teflon spacers as a snapshot in time, where at that moment, that's what he did in an attempt to solve the problems he was seeing. It didn't work out as planned, but was a step to where we are now. Swede used the blogs as a notebook to preserve his progress and to use as a reference for the future. Fortunately for us, he left it here for us to use and share (so we don't have to repeatedly re-invent the wheel). WSM
WSM Posted April 14, 2015 Posted April 14, 2015 (edited) Everything came together tonight so I started my first perchlorate cell experiment. This is a "proof of concept" cell to test the LD anode. After this run, I plan to run the platinized titanium electrode. This is exciting. I'll run it till I can test for perchlorate with methylene blue solution. More later... WSM Edited April 14, 2015 by WSM
WSM Posted April 14, 2015 Posted April 14, 2015 (edited) Everything came together tonight so I started my first perchlorate cell experiment. This is a "proof of concept" cell to test the LD anode.IMGP7771.JPGAfter this run, I plan to run the platinized titanium electrode.This is exciting. I'll run it till I can test for perchlorate with methylene blue solution.More later...WSM That was a premature statement. I just tested for perchlorate and the test is positive! The spot on the right is the LD cell sample, the spot in the middle is the sodium chlorate solution (both with methylene blue solution added) and the spot on the left is the sodium chlorate solution with no added reagent (for a control). The purple coloring is a positive test for perchlorate, and this is after just two hours of running! I'm not stopping the run yet, though. I'll run it as close to completion as possible. WSM Edited April 14, 2015 by WSM
WSM Posted April 15, 2015 Posted April 15, 2015 (edited) The test continues and is progressing in a textbook manner. I do detect some ozone in the vent exhaust, but it's very minor (not the least bit overpowering) and has a scent of "fresh air". The temperature has climbed to between 45o to 50oC and stabilized. The study I've done says this is normal. I've controlled the current input to about 0.1A/cm2 and so far everything looks happy and is operating normally. The voltage at the electrode leads is reading about 4.19 Vdc, which is a little low (according to industrial standards) but at the lower current density I'm running it at, this is expected (it also accounts for resistance in the power leads). The filled tubular leads to the electrodes are a bit warm but not so much as to be a problem for the PVDF compression fittings. Between another enthusiast and myself, we conservatively estimate the run should be complete in three days, or by 19:00 the day after tomorrow. If any of the parameters change dramatically before then, I'll pull the plug sooner; but so far, so good. At 24 hrs I tested for perchlorate with methylene blue solution and got an immediate and strong positive indication. Everything is on track ! WSM Edited April 16, 2015 by WSM
Arthur Posted April 15, 2015 Posted April 15, 2015 Do you have a quantitative test for perc? Not have we perc, but we have perc and it's nn grams per litre. Vogel's Quantitive inorganic analysis comes to mind. Anyone with more recent college time may have a better book, but IIRC vogel is available as free online PDF.
WSM Posted April 15, 2015 Posted April 15, 2015 (edited) Do you have a quantitative test for perc? Not have we perc, but we have perc and it's nn grams per litre. Vogel's Quantitive inorganic analysis comes to mind. Anyone with more recent college time may have a better book, but IIRC vogel is available as free online PDF.An excellent suggestion. Do you happen to have a link to it? A fellow enthusiast and I were discussing this last night and another option would be to determine by the amount of sodium metabisulfite required to neutralize the residual chlorate, how much chlorate was in the solution. Subtracting that weight percent of chlorate should give a fairly accurate estimation of the weight percent of perchlorate in the solution. It's sort of a backwards titration, if you will. Once the amount of perchlorate is determined, we'll have the current efficiency figured out, as well. I believe that the older texts have better colorimetric spot tests than the newer books (which lean heavily on new technology rather than chemistry). WSM Edited April 15, 2015 by WSM
Arthur Posted April 15, 2015 Posted April 15, 2015 Older texts tend to rely on cheaper technology, maybe you have to calculate the results but you don't have to spend 100k on a machine!
WSM Posted April 15, 2015 Posted April 15, 2015 (edited) Older texts tend to rely on cheaper technology, maybe you have to calculate the results but you don't have to spend 100k on a machine!Yup! Thanks for everything. WSM Edited April 15, 2015 by WSM
WSM Posted April 16, 2015 Posted April 16, 2015 At 48 hours the system voltage and temperature have remained constant (of course while running in CC, or constant current mode, the current is rock solid at 15.0 Amps). At two hours after the first 48 hours of running, I've noticed the voltage begining to raise very slightly and the temperature dropping very slightly. I'm beginning to wonder if I'm nearing the end of the run? I plan to run it to 58 hours and see where it is and then decide whether to pull the plug or continue. I also noticed the fluid level dropping about half as much as in the first 24 hours, possibly because less chlorate is there to be converted to perchlorate? We'll see... WSM
pyrojig Posted April 16, 2015 Posted April 16, 2015 (edited) Better watch out !!! We might jump on the band wagon ....if you keep showing such progress!!! Im glad you took the initiate and got the ball rolling again . Thank you . Edited April 16, 2015 by pyrojig
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