How to clean up the silicone oil (e.g. dimethyl siloxane) of beakers after oil-bath heating? I have tried ultrasound treatment with a lot of detergent, heating at 400℃ (can the glass beaker bear higher temperature treatment ) for 2h, but still failed. Thanks in advance.
Use non polar solvents with dielectric constant (at 25 degree centigrade ) not more than 2.2
Thank Michael and Cyril:
Michael, what is the highest temperture the simple glass can bear? What hot concentrated lye mean, 70-80degree? 1M?
Cyril, would you please list several kinds of cheap and safe non-polar solvents with dielectric constant (at 25 degree centigrade ) not more than 2.2?
BEST REGARDS
Peixin Du
To de-grease yes one can use 50:50 NaOH and Na2CO3. The carbonate will reduce the colluding effect of the caustic
First I remove the residual silicone oil with a good laboratory detergent (Alconox) in warm water. Then rinse with DI water and then dry the glassware in an oven at 120C. To remove the white residue I treat the glassware with 5% w/v hydrofluoric (HF) acid in water. I place enough dilute HF inside to coat the inner surface of the vessel and cover it with parafilm and shake until all the white residue releases from the surface. Caution; concentrated Hydrofluoric acid is caustic and causes nasty burns that may require emergency treatment. Be sure to use the proper gloves, lab coat and eye protection. Use plastic ware to work with the concentrated acid and to store the dilute solution. That said the dilute 5%w/v hydrofluoric acid (HF) solution is about twice as strong as vinegar (5% acetic acid). I will admit to using my bare hands to smear the diluted HF over the surface of the glassware back in the day. This is one way to clean glassware down to a fresh non-contaminated hydrophilic surface!
Correction! I used 2.5%w/v aqueous HF, 5% of the concentrated hydrofluoric acid in water, i.e. 50ml of concentrated hydrofluoric acid (48%) diluted to 1.0 liter. If you work with HF, read and heed; http://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=3&cad=rja&uact=8&ved=0ahUKEwjukqLj46LKAhWJRSYKHfl6C5AQFggwMAI&url=http%3A%2F%2Fweb.utk.edu%2F~ehss%2Ftraining%2Fhas.pdf&usg=AFQjCNFbbv7Vdbp8NHDBUylPP7i4Zt2Dcg
Dilute HF is not as corrosive as the concentrated acid. It will dissolve the amorphous silica residue (which is porous and has a large surface area) that forms when you heat silicone oil before it dissolves much if any of the glassware vessel.
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