I have a whole heap of test tubes that have rust stains inside them that I can't seem to remove. I've tried soaking them in 50% acetic acid solution then dilute HCl and they are pretty much the same.
It would be such a waste to throw out all these test tubes.
Any advice would be appreciated.
//EDITED by adam. Reason: make topic subject more descriptive.
TritonX,
The quickest way to clean rust out of test tubes is with conc. hydrochloric acid - fill the test tube for a few seconds to a couple of minutes (depending on severity of stain) then empty into next test tube or back into used conc. HCl bottle (can be used over and over again).
Mal Bradbury
Mazenod College
Just to re-iterate, Oxalic Acid should remove the residue.
If all else fails, Concentrated Sulfuric Acid left for at least a few hours will remove any Rust residue. Fill the Test Tubes just passed the level of rust and let them stand.
As a safety point, make sure the test tubes are adequately labelled that they consist of H[sub]2[/sub]SO[sub]4[/sub].
It may work much more quickly if the H[sub]2[/sub]SO[sub]4[/sub] was heated to allow the hot liquid to begin.
Once you have used the acid for cleaning put this liquid in a bottle and keep it for other cleaning applications, this way you have a cleaning solution and there is minimal waste.
Last edited by Robb on 15 Jun 2006, 21:29, edited 1 time in total.
Dr Robert Crosdale. MRACI. NSS. NSSA. NASA.
Ph.D (Chem), Post Grad Ph.D (Physics), M.Ed, B.Sc (Hons), Dip. Appl. Sc. (Chem)
Lake Munmorah High School.
University of New England.
University of New South Wales.
University of Newcastle.
To understand the Universe from our perspective, we need to look towards our own backyard first for answers.
I am really excited about this site and have printed off quite a few hints!!!
To get back to rust stains- I use a solution of Oxalic Acid for rusty test tubes and glass plates.It is very successful if left overnight.The solution can be reused over and over again saving on wastage.
Very good advice from Lee at Dubbo, oxalic acid is a safer and effective treatment. The use of concentrated acid and heat to clean test tubes is a potentially risky method when weighed against the cost of test tubes, the value of your time or just retaining the rusty TT's for future similar use.
Always consider risk magement and OH & S - YOU ARE IMPOTANT
IF IN DOUBT THROW OUT
My vote again is for oxalic acid... much safer, reusable and effective.Just leave aside for an hour or so.For stubborn strains, soak overnight.
I also use CLR when oxalic acid is low.
Oxalic acid is also great for removing that awful brown Potassium Permanganate stain on glassware.
