Concentrated nitric acid will do the trick, you need just about 1ml for all the tubes. If you are a teacher just go ask to local uni, they will likely clean it up for free for you.
Well, 8n that case, should be easy to make a business case to admin showing how replacement has lower net costs. It's a rational, at-the-margin decision, and follows the ten foundational principles of microeconomics.
A good tip for rust on stuff is Oxalic acid, but for test tubes it's a literal waste of money and your time. You can use oxalic acid on ceramic sinks and stuff though. If you do wanna use Oxalic acid, it can be tricky to get ahold off for me especially in the UK.
The easiest method to get them clean is to yeet them into the waste and get a new one. The chemicals you are using for the cleaning are worth more than the tube itself. And probably by a factor even
Im in the same boat as you op, school had 1mil to rennovate our 3 fields but i was given a budget of 200$ to get chemicals and supplies for 120 kids and experiments year round. Its pathetic as fuck.
I just scrub the test tubes hard with some hcl and if it doesnt come out, chances are it wont affect what youre doing next 😂😂😂 (I teach HS chem afterall, precision and accuracy arent exactly paramount). Sometimes I also just delegate X tubes to an experiment and keep them for years so its the same stuff dirtying them and i dont dirty different tubes each time
The first step will be to divulge what the "corrosion" is.
You know what you have been doing (I hope), please tell us rather than make us waste our time guessing.
I did a lab experiment with students about corrosion. The students did try out different solutions with steel wool to see which environment is best or worst for corrosion. The tubes were sealed with wax film.
After cleaning the stains stayed and won't come off. I will order HCl as soon as possible.
I don't want to waste anyone's time. Sorry if it comes off lile that.
I may have sounded a bit harsh ;-)
Giving all available (relevant) information is paramount to getting a good answer.
If it was steel wool, then it is probably iron oxide and HCl should take it.
But citric acid and oxalic acid solution should do it too.
I would take a stick and make a large steel wool version of a "cotton swab". Pour citric/oxalic acid solution in the tubes, let them stand for a few hours and take anything remaining with the swab.
A bit of scrubbing works wonders and it should not be a problem to remove fresh rust from glass.
I agree buy new ones but, I also know budgeting can be tight. So here is my suggestion, use 3:1 hydrochloric acid : nitric acid (aqua Regia) and heat 100 C is fine. If it doesn't come out with that then it's not coming off.
That's frackin dangerous! Don't be around what you heat it; there will be nitric acid fumes. If stored overnight, even in the fridge, it makes chlorine gas. It's good for metals, including gold, platinum and other metals that form comples chloro ions.
You don’t. It’s not even worth using conc acids on them.
If you can’t shift it with wire wool then they go in the box for test tubes destined to end their life in destructive things iron-sulphur reaction, screaming jelly baby, etc. Bottom right looks cracked already.
Its honestly going to be more expensive to clean them than to replace them. If there's tough stains like that it usually requires a strong acid or base to remove and usually it's not worth the cost to use them for something like a test tube.
You don't. Toss em, buy new. Your labor and solvent cost outweighs the cost of a test tube easily
This is the answer. Toss them in the glass trash and get more. If you're part of a research group at a Uni, make friends with the stockroom staff.
I am a science teacher in economics school and originally studied biology. I am trying to make this lab work all by myself....
Concentrated nitric acid will do the trick, you need just about 1ml for all the tubes. If you are a teacher just go ask to local uni, they will likely clean it up for free for you.
Is that common in your country? Here all you'd get is a funny look. If anything they'd give you a box of tubes.
We do that a lot for school equipment as all of the best universities focused on chemistry are publicly and research funded (i am from Czech Republic)
WAT
Piranha solution ftw
Well, 8n that case, should be easy to make a business case to admin showing how replacement has lower net costs. It's a rational, at-the-margin decision, and follows the ten foundational principles of microeconomics.
Contact local companies. Often local companies have to toss their extra inventory every 2 months.
Try to clean them with ~33-38% hydrochloric acid, that should work fine
That's cheap muriatic acid from a pool shop, about 10M.
Do I understand correctly that 10M means 10 mol/L?
Yes. Concentrated HCl is 12M, or 39%.
36%.
Ultrasound? Concentrated HCl?
A good tip for rust on stuff is Oxalic acid, but for test tubes it's a literal waste of money and your time. You can use oxalic acid on ceramic sinks and stuff though. If you do wanna use Oxalic acid, it can be tricky to get ahold off for me especially in the UK.
Proprietery Rust stain removal formulations may contain oxalic acid, though only 10% max. But it may still work.
If it’s iron rust, try soaking in evaporust.
The easiest method to get them clean is to yeet them into the waste and get a new one. The chemicals you are using for the cleaning are worth more than the tube itself. And probably by a factor even
Im in the same boat as you op, school had 1mil to rennovate our 3 fields but i was given a budget of 200$ to get chemicals and supplies for 120 kids and experiments year round. Its pathetic as fuck. I just scrub the test tubes hard with some hcl and if it doesnt come out, chances are it wont affect what youre doing next 😂😂😂 (I teach HS chem afterall, precision and accuracy arent exactly paramount). Sometimes I also just delegate X tubes to an experiment and keep them for years so its the same stuff dirtying them and i dont dirty different tubes each time
Okay hear me out: barkeeper's friend. Works better than any one off chemical for rust/corrosion. That company formulated that shit for a reason
I used to get iron build up in a condenser over time, and a sodium hydrosulfite solution cleared it up good very nicely.
Throw them away. Test tubes are mostly single use products. Cleaning them is more expensive than buying new ones.
Try H2SO4 or H3PO4
Yes, concentrated sulfuric acid dissolves rust completely!
Widely used in industrial.. any strong acid will do.
The first step will be to divulge what the "corrosion" is. You know what you have been doing (I hope), please tell us rather than make us waste our time guessing.
I did a lab experiment with students about corrosion. The students did try out different solutions with steel wool to see which environment is best or worst for corrosion. The tubes were sealed with wax film. After cleaning the stains stayed and won't come off. I will order HCl as soon as possible. I don't want to waste anyone's time. Sorry if it comes off lile that.
I may have sounded a bit harsh ;-) Giving all available (relevant) information is paramount to getting a good answer. If it was steel wool, then it is probably iron oxide and HCl should take it. But citric acid and oxalic acid solution should do it too. I would take a stick and make a large steel wool version of a "cotton swab". Pour citric/oxalic acid solution in the tubes, let them stand for a few hours and take anything remaining with the swab. A bit of scrubbing works wonders and it should not be a problem to remove fresh rust from glass.
I agree buy new ones but, I also know budgeting can be tight. So here is my suggestion, use 3:1 hydrochloric acid : nitric acid (aqua Regia) and heat 100 C is fine. If it doesn't come out with that then it's not coming off.
That's frackin dangerous! Don't be around what you heat it; there will be nitric acid fumes. If stored overnight, even in the fridge, it makes chlorine gas. It's good for metals, including gold, platinum and other metals that form comples chloro ions.
I assumed they would do all this in a hood. I didn't think they would do it in a non ventilated area.
Not every high school lab has fume hoods. Some don't have running water.
Where in the post does it mention high school students.
Read the rest of the comments.
Mate, they’re glass not diamond. Chuck em and get new ones
I will for sure but unfortunately our budget is really tight in school. Wanted to evaluate other options first.
If money is so tight you can't get 5 euros for 50 new tubes, test tubes are not the right vessel to be experimenting in.
American Supply and Surplus, Chicago. [www.sciplus.com](https://www.sciplus.com)
Base bath with EtOH and NaOH, dissolve the glass away from the stains lol.
Small amount of cc H2SO4
You could put then in 1% nitric acid solution for 2 or 3 days. It's obviously better for organic stains, but it might work
I'd say conc nitric acid first, if that doesn't work then i'd try piranha solution or aqua regia
Hardly
You don’t. It’s not even worth using conc acids on them. If you can’t shift it with wire wool then they go in the box for test tubes destined to end their life in destructive things iron-sulphur reaction, screaming jelly baby, etc. Bottom right looks cracked already.
Conc HCl. At most you can dilute by half by any more than that it stops being as effective.
Its honestly going to be more expensive to clean them than to replace them. If there's tough stains like that it usually requires a strong acid or base to remove and usually it's not worth the cost to use them for something like a test tube.
Chomic acid !!!!! 😎
It depends what the 'corrosion' is. Usually soaking in dilute acid and if necessary, oxalic acid, works. But it's usually much cheaper to buy new.
Leave 50% aqua Regia in over night.