Copper (II) Chloride - Page 1
Forum section: electronics / general

author: X
author_rank: Regular Contributor
timestamp: June 16, 2017, 12:06:48 pm
content: I am familiar with Ferric Chloride and Ammonium Persulphate etchants, but a few years ago I found this video which inspired me to consider copper (II) chloride (his method for CuCl2starts from 2:45):FeCl3makes the board almost invisible in the bath and can leave brown stains, and I'm not sure if it is possible to recycle ammonium persulphate (it turns blue, which I assume is CuSO4). I am aware ferric chloride can be reused until it stops being efficient enough, but then as I understand it, the etchant cannot be recycled.I am considering copper (II) chloride as it seems to be very recyclable. I can obtain 35% HCl fro the hardware store, and plenty of copper cabling, so making it shouldn't be hard, although maybe very slow without H2O2.One thing I am aware of is that CuCl2can react violently with certain metals like Al, and also leave stains (much like FeCl3, but can be recycled easily).For manual etching I use mainly fibreglass or phenolic PCBs (whatever I can get at the time for prototypes), occasionally double-sided, with pitch approx 0.1mm minimum.I have seen only a few posts about cupric chloride on the EEVBlog forums before. For those who have experience with CuCl2+ HCl, what is your experience with it, traps, and how does it compare to etchants like ferric chloride or ammonium persulphate?

author: kerrsmith
author_rank: Regular Contributor
timestamp: June 16, 2017, 12:30:17 pm
content: I use the following method as shown in the video below by ECProjects (jump to the five minute mark for actual etching):This method just uses hydrochloric acid and hydrogen peroxide, for small boards (say 5cm x 5cm) you only need about 25ml of each so it very economical.I have made lots of boards using this method and it always works perfectly and it is quick too - most of my boards have only taken a few minutes each to etch.

author: KD0CAC John
author_rank: Frequent Contributor
timestamp: June 16, 2017, 01:16:15 pm
content: This link screwed up my access to youtube ?I like the idea of recycling , I do not do enough etching at this time to consider that important , but as it accumulates .

author: X
author_rank: Regular Contributor
timestamp: June 16, 2017, 01:35:23 pm
content: Quote from: kerrsmith on June 16, 2017, 12:30:17 pmI initially started by drawing my circuits with a suitable etch-resistant pen, though I have been using the photoresist in more recent years. It has accurate results, but I got a bit of flaky resist because I didn't think of doing a second exposure after developing.Are you using a negative or positive photoresist? Occcasionally I use boards pre-coated with photoresist for very small boards, but this can get expensive.Do you find the solution gets quicker as you etch more boards (more CuCl2in solution)?Quote from: KD0CAC John on June 16, 2017, 01:16:15 pmIt worked for me, but I have edited the link so hopefully it should work for you this time.I am also interested in long-term storage of this etchant. It appears this regains strength as it absorbs oxygen.

author: kerrsmith
author_rank: Regular Contributor
timestamp: June 16, 2017, 02:09:03 pm
content: I do the exact method as shown by ECProjects with negative photo resist apart from the second exposure. I found that doing another exposure sometimes caused very tiny errors in tracks / through holes if you had not fully developed the PCB in the sodium carbonate solution and removed all the un-needed resist in every single hole or along a track edge.The resist is quite hard to see as it is very pale in colour when developing and also I tend to work in a darkened room to avoid accidental UV exposure. Any remaining resist would then be extra hardened so would leave either a solid copper through hole or slightly jagged track when etched. My best results come from a single UV exposure and doing the developing in as dark a room as you can whilst still being able to see what you are doing.As I only use so little solution I only use it once. You could try reusing it but the price is so cheap to make it up I do not bother plus only using it once makes the actual etching process really fast - you can actually see the copper dissolving away.The other reason I only use it a single time is that hydrogen peroxide does have a shelf life so it does not last forever once opened - usually about a year I found. Using it any longer than this and the etching process really slows down.

author: Ian.M
author_rank: Super Contributor
timestamp: June 16, 2017, 02:45:35 pm
content: For more on the practical chemistry of the acid Cupric Chloride etchant system seehttp://techref.massmind.org/techref/pcb/etch/CuCl2.htm

author: jpanhalt
author_rank: Super Contributor
timestamp: June 16, 2017, 03:21:15 pm
content: I have used cupric chloride and ferric chloride almost interchangeably for several years. I feel I get a little better detail with ferric chloride, and it is my first choice other things being equal. Etching with cupric chloride doesn't have as broad an endpoint as ferric chloride, and at least in my hands, over etching can be a bit more of a problem.Cupric chloride needs a bit more excess HCl (e.g., by titration) than ferric chloride, but not too much as it contributes to loss of detail. Some commercial users recommend using a REDOX probe to monitor. Hobbyists can just go by color and judge by the way it works.John

author: KL27x
author_rank: Super Contributor
timestamp: June 16, 2017, 09:12:08 pm
content: I would say a lot of people on the interwebs seem to think HCl and peroxide == cupric chloride. I spent a bit of my own time convincing probably the smartest (in electronics knowledge) guy I know that cupric chloride is not just weak, used up HCl + peroxide.To etch metal, you need two things. Acid is the first. But acid will only etch oxidized metal. So the other thing is an oxidizer.So in HCl and peroxide, you are using the peroxide as an oxidizer. It is indeed a very strong oxidizer... but it is unstable and spontaneously dissociates into water and oxygen as soon as you mix this up. So it is very good etchant for someone who etches very infrequently and doesn't want to build an etch tank. But it can't be stored. HCl and peroxide is also not as accurate of an etchant. It has more undercutting than other etchants.Ferric chloride oxidizes the metal, but this oxidizing agent gets used up in the process. Unlike peroxide, this stuff is stable on the shelf forever. But once it's used up, it slows to a crawl. Adding some HCl will help it continue to work. This creates CuCl2 from the used up ferric etchant. And essentially you will start to have to use this like Cupric, by using air regeneration. And eventually this initial batch of ferric will turn into curpric chloride etchant (with some extra iron contamination in it).Cupric chloride is popular because the oxidizing agent regenerates itself when exposed to the oxygen in the air. To use it effectively, it requires aeration.The way I do it is with a vertical etch tank, bubble wand across the bottom, and I hook this to an air compressor with a regulator. It takes only something like a few psi, probably under 10 for sure. A little fish tank thing will work, but it is quite a bit faster when you get it almost frothy with bubbles.The only thing you need to do is add some more acid and water now and then. I'd say you use up (very roughly) about 1/2 of a turkey baster of 31% muriatic acid for every 6"x4" double sided 1 oz board. But not that you have to add it every single etch... this is kinda where it averages out, IME.Curpric is also too opaque to see the board while etching. Once the board goes in, it changes from the light green mountain dew color to a very dark coca cola with hint of pureed spinach kind of color.In terms of etching accuracy, persulfates are the best. Ferric is close second. And curpric is very close third. Relatively speaking, HCl and peroxide is quite bad. Notice that if you get the HCl concentration of curpric too high, the undercutting starts going crazy, like HCl and peroxide. To put it into perspective, if you etch a 12/12 1 oz board in a cupric bubble tank, and you leave it in 4 or 5x longer than necessary, you can end up with a rough looking 6/18 board that might work, still... or it might have a few broken traces. If you leave same board in HCl and peroxide and leave it in 2x longer than necessary, you will end up with a bunch of broken traces everywhere. At 5x, you would have very little copper left on the board, if any. In practical terms, this means with ferric and cupric, you don't have to watch the board etch and you don't have to worry about hot or slow spots, like you do with HCl and peroxide. With cupric, you just come back at a certain time when you know it's going to be done, and it will be perfect. If it's not quite done and needs just a few more minutes, you can come back in another 5 minutes or 40 minutes. It doesn't matter, hardly, either way. Things don't go south fast or far. I don't even set a timer when I etch. The first board in the tank might etch in only 20 minutes, if it's half oz, and I just don't care. Even it it stays in an extra hour, it will still probably be fine.To get initial concentration, if you can't get peroxide where you live, it will take some time. You need a bubbler, period. Keep that going and before you put the copper in the tank of acid, heat the copper wires/scraps with a blow torch to oxidize the surface, at least. It might take several days to make without peroxide.Compared to ferric:Cupric has a very small store of oxider in it. The etch rate depends greatly on the amount of aeration you give it. An analogy is that cupric has a very small battery in it and relies on the power supply to do the work.Ferric is more like a super big battery, which does the etching self-contained. But it eventually runs out.HCl and peroxide is like an air oxide battery which consumes itself as soon as the battery leaves the factory, whether you use it or not.So if you think you can just put some cupric and a board into a shallow tray, and rock it back and forth once in awhile, like with ferric, you will probably be disappointed, unless you are doing only small boards in a very large volume of etchant. It would probably be more practical for you to use ferric or HCl and peroxide if you don't want to bother with active aeration.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: June 16, 2017, 09:33:38 pm
content: Ferric chloride is recycled by placing the solution in a cathode half-cell (i.e., with an ionic barrier membrane, then an inert anode electrolyte and electrode, like H2SO4 + Pt) and electrolyzing until the copper is all deposited, and the solution is Fe(2+).Then the cell is switched around and the Fe(2+) is oxidized back up to Fe(3+).Persulfate could be regenerated in a similar manner, but formation of persulfuric acid must be done with an inert anode at low temperatures.Tim

author: jpanhalt
author_rank: Super Contributor
timestamp: June 16, 2017, 10:00:50 pm
content: There is a little truth in your statements, but a lot of exaggeration and misinformation too.Quote from: KL27x on June 16, 2017, 09:12:08 pmThat certainly doesn't apply to all metals, particularly amphoteric metals. How do explain the ammonia-based etchants? Here's a link to refresh yourmemory:http://www.chemcut.net/wp-content/uploads/2015/03/alkaline_etch_process.pdfQuoteAgreed.QuoteNo it doesn't. To regenerate it requires aeration. It works perfectly well as a one-time etchant.QuoteBoth are one-electron reactions. That is iron(III) to iron(II) or copper(II) to copper(I). On a molar basic, ferric chloride is 162; whereas, cupric chloride is 134.5. Thus, 1 g of cupric chloride will etch more than 1 g of ferric chloride.QuoteUnfortunately, your analogy is meaningless to me.QuoteThat is exactly what I do with cupric chloride when I use it. Works fine. I do not use the peroxide recipes as they eat my resist.John

author: KL27x
author_rank: Super Contributor
timestamp: June 16, 2017, 10:07:36 pm
content: QuoteThis is not the whole picture. I the stoichiometry is something like 4 to 1. IIRC it takes 2 molecules of cupric to oxidize one copper atom, and it takes 1 molecule of fresh ferric to oxidize one copper. But the byproduct of this reaction leaves two lesser oxidized ferric ions which will oxidize 1 atom of copper. So the ferric ends up 4x as potent of an oxidizer. I could be wrong. Maybe it's only 2 or 3 to 1.** I'm not going to look it up, but I'm probably close enough in theory and am pretty confident in practice. As the oxidizer gets used up, things slow fast, too. If you want fast and consistent etch speed, you need much higher volume of cupric vs ferric, probably at least 3 to 1, if you don't use active aeration. Even taking into the molar weight, I believe you are wrong, gram-for-gram of dry chemical. And since ferric etches faster and has slightly less undercutting and iron is cheaper than copper and because ferric creates cupric as a by product (just add HCl to the old ferric) which will regenerate over time, there is no reason other than staining that you should want to use cupric over ferric if you etch in a tray. Ferric will start out faster and more potent and will continue to work just as well as cupric when it turns into cupric.At any rate, I can etch nonstop with my half liter bubble tank, one 6"x9" board after the other, and aside from the first fast one, they will all have a fairly consistent etch speed. At this point, I'm mostly etching with the "power supply," not the battery. Then I can come back in a month, and do it again. It never needs any maintenance other than adding more acid after every board or two and decanting some of the fluid after every 10 or so, with a turkey baster, to reduce the concentration. I don't have to swap out spent etchant for charged etchant to keep the wheels turning. It's just easier this way.I started out with a tray, too. I transitioned from ferric to cupric. I found I usually added a little peroxide and shot the top of the fluid with a heat gun, because it was pretty slow. Building a good, sturdy etch tank was quite a challenge, but after a few iiterations over several years, I have found the easy way. It costs a bit of $$, though, for the materials.** I think it takes 2 copper atoms per (II) ion, and only 1 iron atom per (III) ion, perhaps? And both are done when they get to (I). I think that's why it ends up so high. Cuz each iron has 2 oxidative states to use. Each copper atom has only 1/2 to give up? IIRC, this is how it ends up 4 to 1.

author: KL27x
author_rank: Super Contributor
timestamp: June 16, 2017, 11:24:33 pm
content: Cupric stains are a lot easier to remove from concrete than ferric. A little acid and peroxide, scrub a bit with a brush mop, and hose down with water. You will not even be able to see them. Ferric takes a lot more acid/etching and removal of actual concrete to remove, completely.QuoteThis is relative. In my bubble tank, I get enough aeration to etch with a deficit of HCl. I can etch even while layer of precipitate forms on the bottom of the tank (when the air is shut off, anyway), half inch high. If you push the reaction hard enough, she moves. Add more acid, and all that precipitate goes back into solution.

author: CatalinaWOW
author_rank: Super Contributor
timestamp: June 17, 2017, 12:47:06 am
content: I can't speak to chemistry or etch accuracy, but cupric has worked fine for me for small hobby boards. I can't speak to timing because I don't etch my boards for a specific time, I monitor the removal and stop when it is done. The etching is fast enough to make this practical, something like 5-10 minutes for one ounce copper at normal room temperatures. I haven't noticed any serious problems with undercutting, but I am not trying to etch traces with trace widths comparable to copper thickness.

author: KL27x
author_rank: Super Contributor
timestamp: June 17, 2017, 12:50:39 am
content: ^@Catalina...5-10 minutes for 1 oz board at room temp does not sound doable with curpric unless your room temp is over 50C. Are you using peroxide and HCl? This is one of my pet peeves. This is not cupric chloride. And you're not etching with cupric until you have more than a trace concentration of copper II.I agree HCl and peroxide is practical for most hobbyists. But calling it cupric chloride is not correct. Totally different mechanism of action.

author: CatalinaWOW
author_rank: Super Contributor
timestamp: June 17, 2017, 01:22:18 am
content: OK, I learn a little chemistry today. I stand by my prior post where I profess ignorance of the subject. I still am thoroughly ignorant, just a little less so.

author: KL27x
author_rank: Super Contributor
timestamp: June 17, 2017, 01:41:58 am
content: I think a lot of us may have been exposed to the idea that cupric chloride and hydrogen peroxide and HCl are essentially the same thing due to some half-baked info put on the web maybe 8-10 years ago from some dude caller the Real Elliot, or somesuch. He suggested that if you use HCl and peroxide, it will eventually turn into cupric chloride (ignoring the fact that the peroxide will breakdown and leave you with watered down HCl with only a tiny bit of copper ions in it and it will stop etching.)Some people took this to consider that cupric chloride is only used up, "watered down" HCl + peroxide. That they are the same thing, just on two different ends of a scale.The actual etchant and oxidizing agent in cupric are both different than what is going on in HCl and peroxide.Regarding accuracy, HCl and peroxide work great for boards up to a point. When you start getting into larger boards of 12/12, or even small boards down to 8/8, you will eventually cross a point where you will end up with a substantially lower yield using this etchant. You will also use more of your time examining the boards for defects. This is a great compromise for most hobbyists doing one-offs and/or using larger traces.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: June 17, 2017, 04:07:11 am
content: Note that the precise situation is complicated by mixed Cu(I/II) species. This is what you see when the solution darkens, and ultimately becomes brown if no oxidizer is added. (Pure Cu(I) chloride, in solution, is actually colorless, but a mixed complex is formed when both are present:http://woelen.homescience.net/science/chem/riddles/copperI+copperII/exp0005/index.html)So the oxidative conditions are continuously variable, depending on concentration of these species.You want to add enough oxidizer (whether H2O2, aeration, or another oxidizer like persulfate, chlorate, etc.) to maintain a clear green solution, avoiding the dark mixed complexes.Tim

author: sleemanj
author_rank: Super Contributor
timestamp: June 17, 2017, 06:40:51 am
content: Adam Seychell's document is worth a read:http://sparks.gogo.co.nz/seychell.pdf

author: X
author_rank: Regular Contributor
timestamp: June 17, 2017, 06:57:16 am
content: Quote from: jpanhalt on June 16, 2017, 10:00:50 pmAs I understand, it can regenerate itself so long as it is exposed to air. However doing this without aeration will make it ludicrously slow.Quote from: KL27x on June 17, 2017, 01:41:58 amI'm pretty certain it does turn into CuCl2, but this depletes the HCl in the process. As I understand you need to add fresh HCl to create tetrachlorocopper ions (CuCl42-) which is what react with the copper metal.It seems the H2O2 + HCl method is good for the initial CuCl2 production, then perhaps subsequent runs can use the resulting CuCl2 + fresh HCl.That is what I am thinking of doing to make the CuCl2 in the first place, as I have lots of copper wire I can strip away, but not enough to be worth much in scrap.

author: sleemanj
author_rank: Super Contributor
timestamp: June 17, 2017, 07:46:13 am
content: FWIW; I etch with HCl+H202 or CuCl2 depending on your opinion, I don't throw it away I just keep using it, I use a splash of H2O2 and HCl every now and then. I am very slack and hap-hazard, so I measure nothing, it's all done by eye. If the etchant looks too dark I add H2O2 (35%) to green it up, if it's going a bit slow I'll chuck in a splash of HCl as well. Now and then I'll evaporate some off to reduce it down.Anyway moral of the story is, it's not critical for a hobbiest, get some H202, get some HCl, and do it, put it in a suitable container when done, and reuse it next time, worst to worst you add a dash of H2O2 and/or HCl to kickstart it again.Just a couple of tips, dilute the HCl until it is not fuming (if your HCl is strong enough to fume), and when adding H2O2 do it a LITTLE at a time and observe the etching reaction before deciding if it needs more, add too much too quick and it will get out of control. It shouldn't be a vigorous reaction, there is no prize for the world's fastest etcher.

author: KL27x
author_rank: Super Contributor
timestamp: June 17, 2017, 10:09:21 pm
content: Sleemanj,I think maybe available chemicals are part of the different perspective. In the US, the highest easily available concentration of peroxide one can buy is 3%. With 3% peroxide, casually using this peroxide and HCl etchant to make your boards and eventually ending up with cupric chloride is somewhat unlikely.* You will just keep diluting your solution unless you are etching every day. The more realistic way to make cupric chloride for us is to continue etching as much scrap copper as possible "while the iron is hot."*To be more clear, if you are etching boards in under 10 minutes, then putting away your etchant until next week/month, there is no way you will be able to keep that up and end up with cupric chloride, using 3% peroxide.

author: KL27x
author_rank: Super Contributor
timestamp: June 17, 2017, 11:22:44 pm
content: QuoteThe situation from local stores is getting pretty bleak, in my neck of the US. I'm getting burned left and right. The HD and Lowes is leading the pack. Want some muriatic acid? The only stuff they carry called muriatic acid is really just chlorination liquid. Call it that, and I don't care. But it's labeled muriatic acid. You want mineral spirits? Look elsewhere. They have "mineral spirits" but it's 75% water, and water isn't even listed in the ingredients. It lists "75% other ingredients special formulated...," of some such nonsense. If they called this "paint brush cleaner" or "paint thinner for water-based paints" that's fine, but it's labeled as mineral spirits.*I have to go to a pool supply store to get cheap HCl, anymore. Personally, I have never purchased high concentration peroxide, before. I'm sure you can get it. Lots of industry use it. It's not sitting on a shelf at your local store. I bet you can buy it at hair salon supply stores.*The irony is that I have an old can of Crown "paint thinner." The ingredients list? 100% mineral spirits. In the old days, mineral spirits were so cheap you didn't even want to call it that. You called it "paint thinner," to sell your mineral spirits. Now, this basic organic solvent cocktail is listed as the name of a product that doesn't hardly contain any.

author: jpanhalt
author_rank: Super Contributor
timestamp: June 17, 2017, 11:47:43 pm
content: @KL27xWhere do you come up with such BS? Why do you seem to feel obliged to make such outlandish comments? Trolling?Quote from: KL27x on June 17, 2017, 11:22:44 pmHere's the truth: muriatic acid:http://www.homedepot.com/p/HDX-2x1-Gallon-Muriatic-Acid-2118-HD/100119310QuoteMore BS. Here's the truth:mineral spirits:http://www.homedepot.com/p/Klean-Strip-1-gal-Odorless-Mineral-Spirits-GKSP94006P/100147127SDS for Klean Strip mineral spirits:http://www.homedepot.com/catalog/pdfImages/4b/4bb28c0f-ca74-4b03-9467-b2eb013961e1.pdfIt is not 75% water.John

author: jwm_
author_rank: Frequent Contributor
timestamp: June 17, 2017, 11:53:03 pm
content: Oddly enough, the most available source of 30% h2o2 has been wacky homeopathy stores. Apparently drinking crazy diluted (the more diluted the better) h2o2 is a thing now. And paradoxically enough, to do it right you have to start out with the least diluted feedstock or the homeopathy faries don't bless it or something even though you dilute it to less than 3%. As a side effect, the local new age shop carries 30% food grade h2o2. (Verified the concentration by manganese dioxide catalyst and measuring oxygen volume. It's the real stuff)

author: KL27x
author_rank: Super Contributor
timestamp: June 18, 2017, 12:39:03 am
content: QuoteTry to buy either of those atmyHome Depot or Lowe's.You can get Kemtech 15% "muriatic acid" which is not muriatic acid. And other various things actually labeled as "chlorinating liquids."And at least the last time I painted anything, a couple months ago, the only thing available at the HD was Kleanstrip "Green Mineral Spirits." Check MSDS on either of these things. What you DON'T see in the MSDS, assume the worst, and you will be correct. The Kemtech ruined my etch tank and I had to dump the whole thing. The Green Mineral Spirits looks like milk. Literally, it is 75% soapy water, best that anyone can tell. It does not hardly evaporate. And it does not mix with oil paint for shit. I don't know where the contractors go to buy this stuff, but it's not the chain stores. The HD is where the local millionaires go to buy shit they don't need, apparently. Or to buy stuff to try and fail to do something before calling a contractor.QuoteMaybe in your local stores, it is different. I can't even buy over 91% isopropyl from pharmacies, and I have asked. There is only one grocery store where I can find it.When you live in farm country, you can buy industrial chemicals, easily. If you live in a cozy suburb of a big city, you might find things are different. Customers of these stores aren't making things. We're just end-consumers of commercial products. And the chain stores fill their aisles with the highest profit margin crap they can get away with. Heck, you want a simple $5.00 stone to sharpen your tools? Two different home depots, nowhere to be seen. One guy didn't even know what I was talking about, like this is some kind of antiquated thing that only rednecks use. They only carry little name-brand diamond plates on flimly plastic, starting at over $30.00.QuoteTrolling, sure. if you say so. Thanks for being on patrol. We salute you for making the forum a better place.If you want to call me out, do it. Look up MSDS, lol. I'm not pretending to be the emperor, and I already acknowledge I'm not wearing any clothes. But you sure seem to have it out for me. I don't see "all the BS," that you pointed out in my posts. If anything, you are factually incorrect in this thread and are actively choosing to disagree on nitpicky and/or subjective matters, and doing it in an obnoxious way. I put that down to my irreverent attitude, in general, lol. I concede this is me, but you also read into it what you will, and it shows a lot about you.This is the third time you have (tried) to call me out in a week. Second time in this thread. I have so far ignored the personal intonation of your posts, but now it is impossible to ignore. If I know anything, I know I make mistakes. Sometimes quite a lot...and I don't care when I do. I own it. So go ahead; try again. I'm sure you will find something else I posted to try to make me a liar. But maybe you should make sure I'm the one that is wrong before you present your evidence with a smirk and proclaim yourself king troll hunter. Cuz I can stand the spotlight. Let's dance!

author: janoc
author_rank: Super Contributor
timestamp: June 18, 2017, 12:53:47 am
content: Quote from: jwm_ on June 17, 2017, 11:53:03 pm"30% food grade h2o2" is a thing today??I didn't know that hydrogen peroxide was "food grade" in any concentration - drinking it would likely do a nice number on your stomach when it combines with the hydrochloric acid there.https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2658134/

author: jwm_
author_rank: Frequent Contributor
timestamp: June 18, 2017, 01:03:41 am
content: Quote from: KL27x on June 18, 2017, 12:39:03 amJust a note, although isoprpynol forms an azeotrope with water so can't be distilled, it is completely insoluable in salt water. So, you can just dump a bunch of salt into your 91% IPA and the pure alcohol and salt water will separate out like oil and water. Just baste off the pure alcohol and you are good. Salt won't contaminate the alcohol as the water will absorb it all. Before you get ideas This doesn't work with ethanol, you will just get salty vodka.I highly recommend nurdrage and nilereds videos to learn how to procure various useful substances from readily available ingredients.

author: CatalinaWOW
author_rank: Super Contributor
timestamp: June 18, 2017, 03:58:04 am
content: Quote from: blueskull on June 18, 2017, 01:09:46 amFood grade for chemicals like these means that there are no other contaminants that would be dangerous and would remain after whatever process (rinsing, washing, evaporating etc.) finished removing an adequate amount of the primary chemical.

author: janoc
author_rank: Super Contributor
timestamp: June 18, 2017, 12:49:35 pm
content: Quote from: CatalinaWOW on June 18, 2017, 03:58:04 amUh ok, makes sense. One learns something new every day. But the concept of using hydrogen peroxide as a part of some "new age" diet or something made my alarm bells go off. Some people drink even bleach claiming that it is a miraculous cancer cure

author: X
author_rank: Regular Contributor
timestamp: June 18, 2017, 01:15:47 pm
content: This is going off topic a bit, but it is possible H2O2 is used in the preparation of the food (baking?), as an oxidising agent of some sort, rather than for direct consumption. This kind of thing would require classification as a food grade reagent.I've got a fair bit of IPA so I may try the saltwater separation trick to see if it works, though surely the salt will contaminate the IPA somewhat?

author: helius
author_rank: Super Contributor
timestamp: June 18, 2017, 01:52:15 pm
content: Quote from: KL27x on June 18, 2017, 12:39:03 amIn California? The homedepot.com webstore will show you if a product is in stock at your local outlet. If you are not affected by the silly "VOC" regulations, you can simply order the correct chemicals and pick them up when the store restocks them.The "Green" nonsense products are motivated by chemical companies wanting to keep a foothold in California. They are also more expensive than the proper chemicals they imitate, which means higher profits.The "Green Muriatic Acid" is adulterated with a weak base like urea to produce less HCl fumes. I'm not surprised it ruined your etch tank!

author: KL27x
author_rank: Super Contributor
timestamp: June 18, 2017, 11:20:58 pm
content: California? No. I don't think it is anything to do with local regulation. I have bought 30% muriatic from hd and/or lowe's probably 3 or 4 years ago. But some months ago when I last ran out, I went to HD, and this Kemtek atrocity was all they had. Box after box on the shelf. I was skeptical because the box says 15%HCl, "85% other ingredients not suitable for spray adjunctant" or such. But if this is all they have, I might as well try it, right? I have a gallon of backup etchant from the overflow, anyway.After pouring more and more of this stuff in my tank and getting a lot of new precipitate* but no etching (none at all... had a board 2/3rd's etched, and it was just frozen in stasis) I went to the Lowe's, and they also only carried this same thing. So I ordered a small bottle from Amazon and eventually bought a gallon at the pool supply store.15% HCl, 15% base? LOL. The box says "Pool Acid" and "Muriatic Acid" on it in big letters, and under that even says "Pool pH lowering agent." There is no indication other than the "85% other ingredients" vaguery that it might be something other than HCl.*It took a bit of rinsing with real HCl to get the gunk out of the tank.

author: AE7OO
author_rank: Regular Contributor
timestamp: June 01, 2019, 10:02:16 am
content: I know it's a old thread, but I just wanted to note that here in Phoenix, AZ, US the local Home Depot only sells two different muratic acids.A Klean-Strip for concrete at 20% HCL/80% H2O at $9.98 for a gallon. The other is a two gallon set at 15%HCL/85% H2O for the same price.Neither of these contain anything HCL and water. The MSDS is your friend here.I use the later combined with 3% H2O2 to etch PCBs with no problems. I will admit however that during the winter months it can take a while to do so(I do all of my etching outside), during the summer here it's not a problem. I use a glass baking dish to etch in and just let the liquid evap and then rinse it out with a little water and add it to a glass jug. I've got about 2 inches of what I assume is copper something dust in it.

author: KL27x
author_rank: Super Contributor
timestamp: June 05, 2019, 10:01:33 pm
content: QuoteI am guessing you are ending with little bright green crystals when it evaporates? If you collect enough, you can make cupric chloride.If you want to get higher fidelity/yield, you have to leave acid peroxide behind. It will hold you back.Sidenote: if you want to etch with pure cupric for high accuracy, you can't put peroxide directly in the tank. In commercial cupric tanks, the regeneration is done a variety of ways, including using peroxide. But the peroxide is added in a separate area from the tank/board and the amount is titrated/tuned to avoid leaving any excess, free peroxide in the tank when the recharged etchant is recirculated back to the tank.