Dear Lab Guy,
We purchased a few of your 10 mL self-zeroing burettes. We are having a problem with leaking out of the bottom of the glass stopcock. The little rubber O-ring seems to not be doing anything or maybe wasn't designed to keep it from leaking. Do you have any recommendations on how to fix it? We run 0.1N sodium hydroxide through it.
Klinton
Hi Klinton,
I believe this is a simple fix. First, the O-ring is designed to prevent the stopcock from falling out if it becomes dislodged. I think what is happening with the leaking is your sodium hydroxide is breaking down lubricating grease that coats the core of the stopcock.
Using “High Vacuum Grease” to re-coat the core should fix your problem. You would just need to take off that O-ring, pop the core out, clear out the bore with a toothpick or a can of pressurized air, and then give it a good wipe down. The grease I recommend is found in almost every lab: Dow Corning High Vacuum Grease.
While you are waiting for it to arrive, you can follow the same procedure and use Vaseline as a quick alternative. This will break down quickly, so not a long term solution but will hold up enough to get you back up-and-running.
I hope this helped and answered your question. Thanks for writing in, and please feel free to write back if I can help in any other way.
Yours in science,
Lab Guy
