WSM Posted June 20, 2015 Share Posted June 20, 2015 (edited) A Spot Test for Chlorates In purifying sodium perchlorate of chlorates, preparatory to making potassium perchlorate; testing for the presence of chlorates is critical. I have at my disposal, three tests I can use; aniline HCl, N-phenylanthranilic acid, and indigo carmine. Indigo carmine would have been my first choice, but since it also tests for sulfites, it'll give a false positive for chlorates if sulfites are present (remember, I'm using sodium metabisulfite to destroy the residual chlorates). My next best option is N-phenylanthranilic acid (or NPAA as Swede calls it). The methods described in literature are either wasteful or hazardous, but recalling discussions I had with Swede many years ago, I've adapted a spot test that Swede suggested, that works well for me: to three drops of test solution in a spot plate, I addthree drops of NPAA solution (0.30 g NPAA in 10 ml methanol, stored in a brown dropper bottle). Next, I addfive drops of 3M HCl solution (30% dilution of full strength [31.45% HCl] pool acid) If a color develops, chlorate is present. This method is working well for me, where indigo carmine fails. I haven't tried the aniline hydrochloride test yet since the NPAA method is proving successful, and is less toxic. WSM Edited June 21, 2015 by WSM Link to comment Share on other sites More sharing options...
schroedinger Posted June 20, 2015 Share Posted June 20, 2015 WSM for a 90ºC i see one big problem. Many MMO anodes are only suited for 70-80 Cº and the same goes for lead dioxide (the one i have is stated to work up to 80ºC and also listed 60ºC as a maximum working temperature to reduce wear).. I don't know about Pt. Did you check what you anodes can take? Link to comment Share on other sites More sharing options...
Arthur Posted June 20, 2015 Share Posted June 20, 2015 Another comment from patent searching is that SMOOTH platinum works as a perc electrode but rough perc ( coated on MMO ) does NOT work Link to comment Share on other sites More sharing options...
WSM Posted June 21, 2015 Share Posted June 21, 2015 (edited) WSM for a 90ºC i see one big problem. Many MMO anodes are only suited for 70-80 Cº and the same goes for lead dioxide (the one i have is stated to work up to 80ºC and also listed 60ºC as a maximum working temperature to reduce wear).. I don't know about Pt. Did you check what you anodes can take? No, and that's a good point. Several MMO formulations are very tough and, I believe, should stand up to the higher temperatures without problems. The "paint and bake" method used in the manufacture of MMO is run at MUCH higher temperatures than the cell could possibly run. The difference is the harsh fluid environment of the cell, as opposed to the oxygen rich, dry environment of the oven or kiln used to make the electrodes. WSM Edited June 21, 2015 by WSM Link to comment Share on other sites More sharing options...
THEONE Posted June 21, 2015 Share Posted June 21, 2015 (edited) I still have not understand, what did you achieve by running the chlorate cell at 100+c ? Edited June 21, 2015 by THEONE Link to comment Share on other sites More sharing options...
Arthur Posted June 21, 2015 Share Posted June 21, 2015 One US patent stated that one patented invention was to run the cell at 100 - 110c because water evaporated from the cell allowing greater concentrations to be accumulated. ALSO cooling to 40c naturally let lots of chlorate precipitate out. Cooler processes need to use power to refrigerate the chlorate cell output liquor to crystallise the chlorate Link to comment Share on other sites More sharing options...
WSM Posted June 21, 2015 Share Posted June 21, 2015 Another comment from patent searching is that SMOOTH platinum works as a perc electrode but rough perc ( coated on MMO ) does NOT work Rough platinum would have more surface area. Too bad they say it doesn't work. Smooth or rough, the problem is the expense of platinum. WSM Link to comment Share on other sites More sharing options...
WSM Posted June 21, 2015 Share Posted June 21, 2015 I still have not understand, what did you achieve by running the chlorate cell at 100+c ? Check out the Patent US 3043757. When you read through it, you'll understand. The whole idea as presented there is intriguing. The patent is dated 1962, when the state of the art was graphite anodes and iron cathodes. Obviously, we've come a long way since then... WSM Link to comment Share on other sites More sharing options...
taiwanluthiers Posted June 21, 2015 Share Posted June 21, 2015 what cell container would have been sufficient for 100c? I mean I don't think anyone makes titanium pots... (could be used as cathode) Link to comment Share on other sites More sharing options...
Arthur Posted June 21, 2015 Share Posted June 21, 2015 IMO stainless steel is good for 120C (or more!) So would titanium. Commercially if you can afford platinum electrodes then a titanium container is no problem. Link to comment Share on other sites More sharing options...
MrB Posted June 21, 2015 Share Posted June 21, 2015 IMO stainless steel is good for 120C (or more!) So would titanium. Commercially if you can afford platinum electrodes then a titanium container is no problem.Stainless seams to be the way to go. One of the commonly refereed to as "acid resistant" variants should be neat. And, given our anode sizes, insulating the darn thing, should do wonders to drive the temperature up. However... Would the evaporation of water really be a necessity? I'm thinking a condenser hooked to the top, and letting the vapor aircool and run back down would maintain the temperature and water-levels preventing it from running dry, while still allowing for the concentration to build up, getting you that precipitation when you finally do cool it off. Since the water volume would be larger at that point, less would of course precipitate out, but it's not going to make a huge difference, and, only for the first run. Refill, and run again, and the difference should be gone. That much more simply stays in the system from the first runt to all the consecutive ones. Well, reading the above it kinda looks like i think i know what i'm talking about, but i should probably have shaped it more like a question. I have no freaking idea, i'm just thinking along the lines "less is more". If the system maintains it self, there is a smaller chance of it burning down the house.B! Link to comment Share on other sites More sharing options...
WSM Posted June 22, 2015 Share Posted June 22, 2015 IMO stainless steel is good for 120C (or more!) So would titanium. Commercially if you can afford platinum electrodes then a titanium container is no problem. Don't forget the electrodes were both platinized titanium and spaced 0.125" (about 3 mm) apart. Part of the described system detailed reversing the polarity occasionally. Using stainless or titanium as a tank, sounds attractive, but the spacing would be a problem I think. Plus fabricating the tank would be a tricky welding job. WSM Link to comment Share on other sites More sharing options...
taiwanluthiers Posted June 22, 2015 Share Posted June 22, 2015 Well you could just buy a pressure cooker and start from there. But I am under the impression that stainless steel would fall apart in short order if used as a container, unless the container itself is a cathode. Link to comment Share on other sites More sharing options...
Arthur Posted June 22, 2015 Share Posted June 22, 2015 Commercially the container is usually the cathode. The whole point of running the cell hot is to evaporate water so that a cell saturated with chlorate at 120C will ppt out chlorate by natural cooling to warm ambient ( 45C) Link to comment Share on other sites More sharing options...
THEONE Posted June 22, 2015 Share Posted June 22, 2015 Just glass will do the job. Link to comment Share on other sites More sharing options...
WSM Posted June 22, 2015 Share Posted June 22, 2015 (edited) Just glass will do the job.Pyrex (AKA, borosilicate glass) should work fine for one of these systems. For example, the tank I used for the LD perchlorate cell would probably work great. I hesitate to limit myself to one material, as several options are out there. PVDF (Kynar) would make a great cell tank, plus be less prone to breakage. Kynar is expensive, though (but not near as costly as it's rich Cousin, Teflon). If you could find an inexpensive, surplus tank made of PVDF, it would make an excellent cell. WSM I often refer to PVDF as "Poor man's Teflon", usually costing about 20% as much, while being nearly as resistant to harsh environments as real Teflon. Edited June 23, 2015 by WSM Link to comment Share on other sites More sharing options...
Mumbles Posted June 22, 2015 Share Posted June 22, 2015 With such a hot and concentrated cell, I'd be concerned about starting to etch the glass and eventually start poisoning the electrodes with silica. I recall 50AE having some potential problems with this a few years ago. I don't recall if he thought it was because of the glass or fluoride in the water. Link to comment Share on other sites More sharing options...
Arthur Posted June 22, 2015 Share Posted June 22, 2015 I agree with Mumbles, glass may be etched. I personally think that glass will be etched and that mobile silicates will poison the electrodes, possibly connected also to pH control and the range within which control is good, strong alkalis often etch glass. Just put the best wine glasses in a dish washer to see what happens in a 15 minute cycle, in an alkaline cleaner. I like the idea of a plastic (PVC it's cheap!) tank but would 90c permit enough evaporation to keep the concentration up enough. Link to comment Share on other sites More sharing options...
WSM Posted June 23, 2015 Share Posted June 23, 2015 (edited) I agree with Mumbles, glass may be etched. I personally think that glass will be etched and that mobile silicates will poison the electrodes, possibly connected also to pH control and the range within which control is good, strong alkalis often etch glass. Just put the best wine glasses in a dish washer to see what happens in a 15 minute cycle, in an alkaline cleaner. I like the idea of a plastic (PVC it's cheap!) tank but would 90c permit enough evaporation to keep the concentration up enough. Actually, PVC is only rated to 60oC, where CPVC can go as high as 93oC. The down side of CPVC is it costs about five times as much as PVC. On the other hand, PVDF (Kynar) is rated to withstand much greater temperatures without degradation (up to 300oF or 149oC), but the cost is very much more than PVC or even CPVC. Like I said, there are MANY options. WSM Edited June 23, 2015 by WSM Link to comment Share on other sites More sharing options...
THEONE Posted June 24, 2015 Share Posted June 24, 2015 Not only i have already operated my cell under 80°c with a 4L glass jar, but also it is not even a pyrex glass. I have never had any problems. Link to comment Share on other sites More sharing options...
schroedinger Posted June 24, 2015 Share Posted June 24, 2015 I had the problem with etched glass. But only when no ph controll was used. Link to comment Share on other sites More sharing options...
Arthur Posted June 24, 2015 Share Posted June 24, 2015 My personal opinion is that pH control done well is essential to running a cell in a glass jar, glass is certainly slowly soluble in high pH liquids, where the glass might go is debatable. Link to comment Share on other sites More sharing options...
THEONE Posted June 24, 2015 Share Posted June 24, 2015 According to ph control, Swede said "0.057 ml of concentrated (32%) HCl per ampere, per hour, with the HCl delivery cut by 33% after the chlorate crystals begin to form." If i am going to add all the time chloride crystals, the 33% cut of HCL still must be done or not ? Link to comment Share on other sites More sharing options...
WSM Posted June 24, 2015 Share Posted June 24, 2015 Not only i have already operated my cell under 80°c with a 4L glass jar, but also it is not even a pyrex glass. I have never had any problems. I haven't had problems with my one gallon (3.785 L) glass pickle jar, either. I am aware that a strong alkali can and will etch glass, such as when a chlor-alkali cell has a diaphragm between the anode and cathode and one side (the cathode, I think) creates hydroxides. But with an open cell like we use for chlorates, no. WSM Link to comment Share on other sites More sharing options...
WSM Posted June 24, 2015 Share Posted June 24, 2015 I had the problem with etched glass. But only when no ph controll was used. I suspect the HCl used to control pH would neutralize the OH- as soon as it forms. WSM Link to comment Share on other sites More sharing options...
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