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Chemistry Solutions
Dear Labby,
I am a new teacher inheriting a 20-year-old stock room. Looking over the available equipment, the majority of my Bunsen burners have collars that are fused in place (preventing the air flow to be adjusted). Is there anything I can do to separate them, or are they a lost cause and need replacement?Sincerely,
Baffled by Burners
Dear Baffled by Burners,
Thank you for your question! Old stock rooms are an unfortunate problem that many new teachers encounter, and we applaud your desire to get in there and find the best ways to use what is available to you!
The two most common types of laboratory burners found in high school classrooms are Bunsen burners (where the air intake is controlled by adjusting the hole position of a collar around the barrel) and Tirrill burners (where the air intake is controlled by raising or lowering the barrel on a screw mechanism). See the Flinn Laboratory Burner Selection Guide or the Bunsen Burner Infographic from Compound Interest for more information. Both models can become clogged from either oxidation or from burnt-on chemicals that have been dropped onto the burner during labs like flame tests. Freeing the stuck parts involves some chemistry!
Most lab burners are made from brass (copper/zinc alloy). Some also have a nickel coating. Smaller components in the burners may contain stainless steel (mostly iron with chromium and other elements alloyed). When cleaning these useful laboratory workhorses, it is important not to use substances that will react with the metals and alloys that compose the burner parts. For example, I’ve seen online posts where people attempt to clean the burners with hydrochloric acid, but this is not a great method, as prolonged exposure to HCl will cause the zinc from the alloy to begin to oxidize, weakening the walls of the burner and making it unsafe to use. Following is list of steps you can use to clean off (and therefore un-fuse) the burners. You should begin at step 1 and only progress through the list if the steps you try are ineffective.
1 |
Turn the burner upside down and tap gently, but firmly against the side of the sink so any trapped, but still loose, chemicals can simply fall away. If this method is sufficient, it is still a good idea to take a moment to dry-brush the burner afterward. Disassemble the parts and take a dry test tube brush or toothbrush (bristles should be stiff, but made from soft material like plastic or fiber – not metal) to brush away any dried chemicals that you can. Gently wipe all parts with a paper towel to remove any remaining dust before reassembly. |
2 |
Disassemble as much of the burner as you can. Soak the parts for an hour in a hot soap or detergent solution. Using dishwashing gloves (or solvent gloves) for grip, hold the shaft/collar under running cool water and try to twist the collar. Whether this works or not, thoroughly rinse away any remaining soap/detergent from the parts before trying the next step, so the soap/detergent does not cause interfering reactions. Leave the parts disassembled. |
3 |
Oxalic acid soak – no more than an hour, checking every 15 minutes. Oxalic acid is a well-known industrial rust remover. It is less corrosive than hydrochloric acid and its weak acid equilibrium can assist in the breakdown of a variety of chemicals. Create a bath of 5-10% Oxalic acid in warm, but not hot tap water. Soak the burner parts for 15 minutes, then (while wearing solvent gloves and keeping the parts in the bath) work a test tube brush over the trouble-spots to see if the corrosion or chemicals are wearing away. If needed, continue soaking and repeat the brushing every 15 minutes for up to an hour. When you are finished, be sure to dispose of the solution according to your local guidelines! Bar Keeper’s Friend cleanser (not the soft cleanser or the multipurpose spray) is a cleaner with oxalic acid as the active ingredient. This can be used in place of oxalic acid. Please follow the instructions on the product. |
4 |
Sorry! At this point, if the steps above do not fix the problem, then it is likely you will need to discard the burners. |
Yours in Chemistry,
Labby