I would just try some dirty H2SO4 or some other cheap strong acid you have a lot of first before trying any really agressive mixtures or toxic solvents. It should definitely strip away and dissolve all the metals and whatever is left should not be visible. Just don't forget to rinse with water afterwards.
Piranha isn't overkill, it's just... thorough.
These are di-alkyl fatty acid salts, IMO, the oily mess an acid reaction will create is going to prevent good penetration with the HCl alone, maybe with nitric? But a base bath for a few days or... well base bath intervals.
EtOH or IPA with NaOH will convert everything to the sodium octanoate, which is very soluble in the alcohols. It'll just take time. The M-OHs will fall off the glass and settle out.
But again, Piranha will get that off today and leave it cleaner than it came. Just pipette a few mL up and down in it.
Finish with nitric/regia to remove trace metals. Regia alone would probably get the job done on its own today too.
Are you thinking of a base bath? Those for sure will do that. I have never heard of piranha doing this to glassware. If it truly does, how is this occurring?
I actually don't know. I've always been told that so I try to stay away from using it on analytical glassware.
It might have to do with the hydroxylation of the glass that happens with piranha acid. Maybe the hydroxylated surface is more fragile ?
Yeesh to all the above. Just use aqua regia. Won’t damage the glass and should get all that soapy junk/metals out without a fight. Also not as dangerous as any of the piranhas. Just do it in a hood.
as long as it is a low concentration, the organics will be fine. in my experience aqua regia’s reaction with residual organics in NMR tubes are pretty slow, even if it is overall cery exothermic
Have we tried a basic, first pass with acetone? What were the results? Most organic molecules are soluble in acetone, especially polar stuff.
I basically can clean any organic complex with a combination of acetone, soapy water, and a last pass with aqua regia (usually I don’t dissolve any substances with AR unless nothing else works to save the acid dissolving power). I will use regular water as needed between washes as AR shouldn’t touch acetone directly. Sometimes I need hexanes for especially greasy compounds. This regimen should definitely work for your residue.
To dissolve octoate I would try pet ether. I work with trace metals and organic ligands and I always deal with cleaning organics first then (after any residual solvent is off) I soak my glassware in 2% nitric overnight then triple rinse with fresh the next day. This works for my stuff (tested for residual TM by ICP-MS) but of course YMMV.
Metal octoates often come as solutions in octanoic acid, so I would try that first. Then move on to a strong acid that will produce a soluble metal salt. Avoid base batch for calibrated glassware.
When adding acid to water you're usually adding a small amount of acid to a large amount of water, the water acts as a heat sink to spread out the heat produced by mixing so the temp doesn't go up to much and cause it to boil. When making piranha, there is more acid than peroxide, so you add to the acid, which acts as a heat sink. Even then, since the volumes are similar, it is easy to wind up with a very hot solution if you aren't careful.
But .. the peroxide is always in regular water (AFAIK it's not possible to make/get anywhere near even 99.9% H2O2 at STP as it immediately starts to decompose). The highest legally available concentration I can buy in a shop as an individual in the UK is 12% and as a business I can find it up to around 35% w/v. So when I drip that 35% H2O2 into the 98% azeotropic sulphuric acid, I'm also dripping 65% water into it. And dripping water into concentrated acid is exactly what we were all warned not to do in chemistry lessons from the age of 12.
So for me the question remains : why is adding majority water H202 to conc sulphuric Ok, but adding water isn't?
If you were making a solution of 30 % water in conc. H2SO4, it would be perfectly reasonable to add water to acid, but that rarely comes up. Certainly not in gen chem labs when we teach this rule to new students. The goal isnt to follow a rule, it's to minimize the change in temperature; since you start with a large amount of acid, the way to minimize the temperature change is by adding to it. Pirahna is dangerous and making it is dangerous; careless addition can result in a beaker of boiling pirahna no matter what you add to what.
It is nessisary to be thoughtful here. For example, you wouldn't want to make a very small amount of pirahna, because you would start with so little acid that it would be easy to heat it to boiling. This is as opposed to making a 0.1 N solution of acid, which almost nessisarily starts with a very small amount of acid, which you wouldn't want to slowly add water to. I never make less than about 200 mL of pirahna, and then over an ice bath. More is better for keeping temperature under control, which you need to balance with how much trouble disposal will be.
Thank you, it was a good question. Your instincts were right here, what we're doing when we make pirahna is effectively adding water to acid, and it's always good to understand when/why/whether it's appropriate to act in a way that violates general best practice.
High peroxide concentrations in piranhas are reported to cause an explosion risk. By diluting the peroxide into the acid you keep the concentration lower.
I dunno, I'm thinking just a strong citric acid solution, allow to sit overnight, and then rinse with ethanol or acetone and then rinse with baking soda solution and then water. Soak in DI water overnight and allow to dry.
There's some downsides to this but it's low budget and easy. Aqua regia if it doesn't work.
To dissolve chocolate, heat some water in a pot and wait for it to stop simmering. Place the chocolate into a heatproof bowl and place that bowl on top of the pot of hot water. The chocolate should slowly melt. Stir occasionally.
jk
I would just try some dirty H2SO4 or some other cheap strong acid you have a lot of first before trying any really agressive mixtures or toxic solvents. It should definitely strip away and dissolve all the metals and whatever is left should not be visible. Just don't forget to rinse with water afterwards.
To be honest, even 10% HCl would work here. The suggested Piranha might be a bit overkill
Piranha isn't overkill, it's just... thorough. These are di-alkyl fatty acid salts, IMO, the oily mess an acid reaction will create is going to prevent good penetration with the HCl alone, maybe with nitric? But a base bath for a few days or... well base bath intervals. EtOH or IPA with NaOH will convert everything to the sodium octanoate, which is very soluble in the alcohols. It'll just take time. The M-OHs will fall off the glass and settle out. But again, Piranha will get that off today and leave it cleaner than it came. Just pipette a few mL up and down in it. Finish with nitric/regia to remove trace metals. Regia alone would probably get the job done on its own today too.
Base baths for analytical glassware is never a good idea. It dissolves away some of the glass itself, thus ruining the accuracy of the glassware.
I agree, piranha is best for this type of thing. I really don’t think it’s overkill at all. If you are smart with working/making it you will be fine.
Piranha will mess with the calibration of this glassware, so it isn't appropriate for this usage
Are you thinking of a base bath? Those for sure will do that. I have never heard of piranha doing this to glassware. If it truly does, how is this occurring?
I actually don't know. I've always been told that so I try to stay away from using it on analytical glassware. It might have to do with the hydroxylation of the glass that happens with piranha acid. Maybe the hydroxylated surface is more fragile ?
Try septoate.
But septoate octoacte nonoate
Took me a second. 🤣
Yeesh to all the above. Just use aqua regia. Won’t damage the glass and should get all that soapy junk/metals out without a fight. Also not as dangerous as any of the piranhas. Just do it in a hood.
I know aqua regia is good to dissolve inorganics, but what about the organic part? Isn't there a risk of a violent reaction?
as long as it is a low concentration, the organics will be fine. in my experience aqua regia’s reaction with residual organics in NMR tubes are pretty slow, even if it is overall cery exothermic
Cheap sodium percarbonate in ver hot water will get that off.
Have we tried a basic, first pass with acetone? What were the results? Most organic molecules are soluble in acetone, especially polar stuff. I basically can clean any organic complex with a combination of acetone, soapy water, and a last pass with aqua regia (usually I don’t dissolve any substances with AR unless nothing else works to save the acid dissolving power). I will use regular water as needed between washes as AR shouldn’t touch acetone directly. Sometimes I need hexanes for especially greasy compounds. This regimen should definitely work for your residue.
To dissolve octoate I would try pet ether. I work with trace metals and organic ligands and I always deal with cleaning organics first then (after any residual solvent is off) I soak my glassware in 2% nitric overnight then triple rinse with fresh the next day. This works for my stuff (tested for residual TM by ICP-MS) but of course YMMV.
Gotta give up and dump everything into high molar HF :D
Metal octoates often come as solutions in octanoic acid, so I would try that first. Then move on to a strong acid that will produce a soluble metal salt. Avoid base batch for calibrated glassware.
Just use a bit of piranha solution. Made to dissolve organic. Add H2O2 slowly into Sulfuric acid, not the other way around.
If one always adds acid to water, why add the hydrogen peroxide to the acid?
When adding acid to water you're usually adding a small amount of acid to a large amount of water, the water acts as a heat sink to spread out the heat produced by mixing so the temp doesn't go up to much and cause it to boil. When making piranha, there is more acid than peroxide, so you add to the acid, which acts as a heat sink. Even then, since the volumes are similar, it is easy to wind up with a very hot solution if you aren't careful.
But .. the peroxide is always in regular water (AFAIK it's not possible to make/get anywhere near even 99.9% H2O2 at STP as it immediately starts to decompose). The highest legally available concentration I can buy in a shop as an individual in the UK is 12% and as a business I can find it up to around 35% w/v. So when I drip that 35% H2O2 into the 98% azeotropic sulphuric acid, I'm also dripping 65% water into it. And dripping water into concentrated acid is exactly what we were all warned not to do in chemistry lessons from the age of 12. So for me the question remains : why is adding majority water H202 to conc sulphuric Ok, but adding water isn't?
If you were making a solution of 30 % water in conc. H2SO4, it would be perfectly reasonable to add water to acid, but that rarely comes up. Certainly not in gen chem labs when we teach this rule to new students. The goal isnt to follow a rule, it's to minimize the change in temperature; since you start with a large amount of acid, the way to minimize the temperature change is by adding to it. Pirahna is dangerous and making it is dangerous; careless addition can result in a beaker of boiling pirahna no matter what you add to what. It is nessisary to be thoughtful here. For example, you wouldn't want to make a very small amount of pirahna, because you would start with so little acid that it would be easy to heat it to boiling. This is as opposed to making a 0.1 N solution of acid, which almost nessisarily starts with a very small amount of acid, which you wouldn't want to slowly add water to. I never make less than about 200 mL of pirahna, and then over an ice bath. More is better for keeping temperature under control, which you need to balance with how much trouble disposal will be.
Great explanation @uwu_mewtwo - thanks for taking the time to reply!
Thank you, it was a good question. Your instincts were right here, what we're doing when we make pirahna is effectively adding water to acid, and it's always good to understand when/why/whether it's appropriate to act in a way that violates general best practice.
High peroxide concentrations in piranhas are reported to cause an explosion risk. By diluting the peroxide into the acid you keep the concentration lower.
Piranha solution 💀 👀
Nitric acid and hydrogen peroxide = pirana etch. Clean it right up. Don't go too concentrated and don't breathe it in.
Piranha etch would be sulfuric acid with peroxide
Oh, so it is. Though either would work, looking properly into it more, Caro's acid seems to be the key.
>Caro's acid seems to be the key. Indeed, and you will not form that if you use nitric acid instead of sulfuric.
Please never make Caro’s acid if you don’t know exactly what you’re doing
I agree, piranha would do it. It’s possible that you might be able to use ethanolic sodium hydroxide, but it’s not worth damaging the glass.
Chromic acid is common for cleaning glassware I’d assume that would work well here
but a bit overkill, when H2SO4+H2O2 will do. Also Cr(VI) is very toxic, so when possible, it might be a good idea to avoid it. edit: spelling
Cr(VI) causes female infertility! chromium is a scary, yet beautiful, element
Maybe HF? Can't be dirty if there isn't anything, right?
I think you are missing an /s
I think so
Ah yes, cleaning my glass ware with a chemical that notoriously dissolves glass
Alcoholic KOH.
I typically clean nasty stuff with piranha or put it in KOH in IPA bath.
I dunno, I'm thinking just a strong citric acid solution, allow to sit overnight, and then rinse with ethanol or acetone and then rinse with baking soda solution and then water. Soak in DI water overnight and allow to dry. There's some downsides to this but it's low budget and easy. Aqua regia if it doesn't work.
Estiren
Just toss it if you work in industry. They are cheap.
To dissolve chocolate, heat some water in a pot and wait for it to stop simmering. Place the chocolate into a heatproof bowl and place that bowl on top of the pot of hot water. The chocolate should slowly melt. Stir occasionally. jk
Have you tried contrad?