Dr J: Ok, this P1000 pipette seemed to be having problems yesterday, perhaps due to some fluid inside. Let me show you how we check if it's all right or not.
Tech: Ok.
Dr J: I'm pulling up 1 mL of water here and we'll weigh it on the scale.
Tech: Oh?
Dr J: See? It should weigh 1 g, but it's only weighing 0.7 g, so there's something dreadfully wrong with it.
Tech: Oh, right.
[pause]
Tech: How did you do that? From milliliters to grams? I'm not so good at conversion factors.
15 years ago
14 comments:
Okay now you can wonder WTF they were teaching him at big wig university
it's easy to forget, but there is a conversion factor at work
the specific density of water
I didn't think it was easy to forget that density is the conversion factor between mass and volume. Nor that the density of water is 1. (As is its specific gravity, which I think you meant to write, but the specific gravity only tells you its density relative to water.)
oh dear, even I could do that conversion at 22...
Wow, not knowing how to pipette I understand, but I would have been mortified if one of my high school students I taught had this exchange with you. I would not have expected this conversation from a college graduate in the scienes.
oh wow....much more troubling than not knowing how to use a pipetman--back to basic chemistry for them...
ok, forget undergrad not teaching him/her this; this is something you learn well before that! As in middle school! This person is a paid tech?!?
OH DEAR.
millimeters to grams... and milliliters tograms... ;)
but seriously? That person has worked as a tech before? Sad to hear about their old pipettes. Bet they were never calibrated....
In my lab we have to do this when "learning" the proper way to pipet. To make sure everyone in the lab is doing this correctly we demonstrate with a specific pipet exactly what you mentioned above.
I'd have explained that I use a modified version Einstein's equation for interconversion of mass and energy to convert liquid units to solid units.
And then told him that's why you can't do it in the dark as you won't have a c-squared to go by. Or some such gibberish. Have fun with it, Dr.J.
Then let him in on it later, of course.
Waaaaah. I had to teach our last tech how to pipet- but she had a bachelor's in PSYCHOLOGY. What's his excuse?
to be fair, the specific density of water at room temperature (25 deg C) is 0.9970 gm/cm^3.... and you'd have to know that a ml = cm^3...
Really? Because I had this conversation with an undergrad the other day, where I just explained it to him up front, and I think he got it. I don't expect everyone to remember everything if they've never done it before. I do expect them to remember after I tell them once. Here's to Tech's future success at learning!
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