odd dinner conversation

[cellio]

The question (not mine): if you were building a thermometer (the kind that lives in your medicine cabinet at home), what range of temperatures would you support? I said the problem was insufficiently specified, but that my baseline would be 96-106 and if there's no appreciable expense in widening it, I'd go in the range of 90-110 or -120, because why not. But the problem was still insufficiently specified; I was assuming digital readout, not a column of mercury in a usually-illegibly-marked tube. In the latter case, you want the minimum useful range, because you've got limited real estate for the markings. If you could have those 10 degrees occupy 80% of the tube and have the rest be compressed that'd be different, I said.

So Dani challenged that -- why assume that the tube is uniform? I said because otherwise you're out of the price range of medicine-cabinet thermometers. This, in turn, led to speculation about how that type of thermometer is manufactured; I argued for a large uniform (hollow) rod that's cut to length with ends then treated (seal at one end, mercury + bulb at other), while he argued for individually molded. (Insert tangent about plastic vs. glass here.) Of course, neither of us actually knows anything about this; we're trying to make intelligent guesses and apply design principles from other fields.

I don't think we're the only people who have weird speculative conversations like this, but I never seem to notice stuff like this coming from other tables in restaurants. On the other hand, we haven't been kicked out of any restaurants for annoying the neighbors either. (On the third hand, it seems to take a lot to produce that result.)

Comments

[kayre]

We do it all the time.. the kidlet winces when one of us grabs a pen and a clean napkin. Though nowadays she's likely to join in at least a bit.

Restaurant Conversations

[dagonell.livejournal.com]

Try this one! The writer's group I'm involved with, The Thundering Word (Poetry reading on 11/7, published in Artvoice, yes!) was helping one member work on his murder mystery. We said the problem with the chapter was the way the body was disposed of. So, we spent some time discussing how to dispose of the body so that it would be found at the right time plot wise. It was about then that we realized the off duty police officers at the next table were taking an interest in our discussion! :D

[alice-curiouser.livejournal.com]

Ya'll are real geeks, you know that? ;)

[cellio]

Pens/napkins and from-memory halachic citations are about equally likely for us. :-)

Re: Restaurant Conversations

[cellio]

Oops. :-)

[cellio]

Why thank you! :-)

[alienor.livejournal.com]

This, in turn, led to speculation about how that type of thermometer is manufactured; I argued for a large uniform (hollow) rod that's cut to length with ends then treated (seal at one end, mercury + bulb at other), while he argued for individually molded. (Insert tangent about plastic vs. glass here.)

FWIW, My guess (as a ceramist who researches bricks, not glass, though I did have a few glass classes) would be for individually molded. The treatment of the ends would require the glass to be returned (at least partially) to the viscous state, which could mess up the hollow tube.


No, I don't think you're the only ones who have those type of conversations either!

[alienor.livejournal.com]

Yes! I've lost count of the number of napkins I've used in this manner. It's even better when you're at one of those places with the craft paper and crayons, though. ::grin::

[cellio]

One of the downsides of better restaurants is that they give you cloth napkins and tablecloths instead of paper napkins and placemats! It's not just that we're philistines who can't appreciate fine dining; it's that we're missing important tools that are necessary for dinnertime conversation!

[cellio]

I was speculating (again, no real experience here) that it's easier to cut 6" pieces off of a long rod and then apply a torch to each end for fine-tuning -- that this wouldn't mess up the main body -- than it is to individually cast (is "cast" the right word for glass?) them. And you've still got to get the mercury in there, so it looks like at least a two-stage process (make, fill/seal) rather than being doable in one fell swoop. And I guess you would have to mold it in two lengthwise halves (with some sort of inset) in order to guarantee the inside diameter of the tube. Hmm, sounds complicated. The alternative would seem to be forming the tube around a rod (guaranteeing a fixed diameter) and then removing the rod and filling/sealing.

[geekosaur]

The structure of a glass thermometer convinces me that one end is sealed afterward; I'd guess that it's the top end, after filling the bulb with mercury. Whether it's initially formed that way or not is an open question but I could see both ends being sealed afterward.

It's potentially possible to mess up the tube during sealing, but not all that likely; you could form the bulb end from the rod segment with just enough air going through the tube to (a) keep it open and (b) inflate the bulb slightly, then fill the tube, then put a small drop of molten glass on the other end to seal it. (I don't know if they're currently mass-produced that way, but it wouldn't surprise me to find that they were initially created as I described.)

[siderea]

FWIW, My guess (as a ceramist who researches bricks, not glass, though I did have a few glass classes) would be for individually molded. The treatment of the ends would require the glass to be returned (at least partially) to the viscous state, which could mess up the hollow tube.

Actually, my understanding is that glass tubes have some fascinating properties when heated to a plastic state. For instance, if you take a tube an heat it in the middle, then draw the two solid ends in opposite directi ons, you get... a really amazingly thin tube of glass. This is, in fact, how extremely fine pipettes used to be (and may yet be for all I know) manufactured, I was told by the lab instructor who made us do this. :) You can actuall spot-heat glass pretty well, so heating only the end to a fusable temperature while leaving the rest alone is feasable.

That said, if I wanted a to seal the end of a glass tube while making sure that the tube remained a consistent diameter, I'd either: (1) just have a plug of metal up the center (only works on one end, but works really well) when closing it or (2) heat the end of the glass to the melting point plus some, and pinch it off really fast/abruptly, using momentum to keep the rest of the shape stable or (3) dip the end in molten glass, or more precisely, put a glob of molten glass on the end. That's my favorite to win.

I suspect as an industrial pro cess it would b e possible to get either (2) or (3) to have sufficiently consistent results not to wack out your calibration.

I'm envisioning a mechanical process which goes: tubes cut into lengths; mounted on pipes; a glob of molten glass put on top end and a timed, pr essurized blast of air feeds up through the pipe to form a consistent-volume bulb; pipe removed, mercury+air added; glob of semi-molten glass daubed on top.

I think that will get you a more consistent result than two lateral halves fused together, but IANACE.

[browngirl.livejournal.com]

I don't think we're the only people who have weird speculative conversations like this,

You're not. ;)

Also, I for one am amused when I hear weird conversations drifing over.

[goljerp]

I think that I'd agree with others here in speculating that the tube is more likely than the mold. As someone else noted, it's easy to heat one end of a glass tube without effecting the temperature of the rest of it; this is especially important when considering that you want the mercury to stay in the liquid state. (Although it's not easy to get Hg to boil (346.68 degrees C), it will evaporate fairly easily. To quote from the CRC Handbook of Chemistry and Physics, 71st Edition,

Mercury is a virulent poison and is readily absorbed through the respiratory tract, the gastrointestinal tract, or through unbroken skin. [...] dangerous levels are readily attained in air. Air saturated with mercury vapor at 20 degrees C contains a concentration that exceeds the toxic limit many times. The danger increases at higher temperatures. It is therefore important that mercury be handled with care.

(20 degrees Celsius is 68 F, or "room temperature")

signs of the times

[eub.livejournal.com]

Last time I bought a thermometer, the drugstore had a dozen digital models with features and batteries and no doubt the bad behavior of all computers, plus one cheap analog one in dusty boxes shoved to the back of the shelf. It used a gallium alloy (http://www.1thermometer.com/FAQ_s/faq_s.html); mercury seems to be deprecated.

Re: signs of the times

[goljerp]

Cool. Thanks for the pointer about the gallium alloy... I can't see why anyone would want a digital thermometer with a non-mercury analogue one available. Computers are cool, but not everywhere.

Re: signs of the times

[cellio]

I much prefer the idea of a conventional thermometer to a digital one, because the laws of physics are a little more reliable than computers. I have a mercury (gallium?) thermometer. But if I needed to use it more than once every several years, I'd have to switch to a digital one because finding someone else to read the results for me all the time would be too much of a pain. The bigger digital readouts at least allow me to use the tool without assistance.

(I have trouble with sixteenths of inches -- let alone milimeters! -- on rulers, too.)

Re: signs of the times

[cellio]

Thanks for the link to the gallium thermometer. I am intrigued by their mention of a version with an easy-to-read display.

I, too, had no idea that mercury had been deprecated.

[dagonell.livejournal.com]

And I reserve the right to inquire if a *truly* interesting comment comes drifting forward! :D

"After you've learned how to put a diaper on a four-handed child, the regular kids are a piece of cake."

"Uhmmm, excuse me, miss. I couldn't help overhearing."

[She was a volunteer at the local zoo and had to put diapers on chimps.] :D

Re: Restaurant Conversations

[jducoeur]

Oh, heck -- that's nothing. I just spent the weekend writing an off-the-cuff LARP (which I really ought to write up in my blog). We wound up creating a game where the players are a bunch of Nazi occultists trying to head off the fall of Berlin in April of 1945.

So there we are, having drawn a pentacle on the floor in masking tape, surrounded by candles, with people speaking loudly in bad German accents about the human sacrifice they're about to make. In the common room of a dorm. At Brandeis University (which is almost entirely Jewish).

We wound up posting guards at the entrances to the room, because we so did not want people wandering into the middle of this scenario unawares...

Re: Restaurant Conversations

[cellio]

Oh my.

Yes, a guard at the door sounds quite wise under those circumstances!