beastmaster - 13-2-2010 at 10:35
For a distilling head what kind of thermometer would you use. A full immersion(Its immersed in vapor?) Or what. I never gave it much thought tell
I was getting ready to buy some new ones. Thanks.
chemrox - 13-2-2010 at 12:21
Thermometers are calibrated to a mark on the stem. For a distilling head you would want one that is calibrated such that the measuring portion (bulb
to line) is in the head. The bulb should be just below the takeoff so that the thermometer measures the vapor temperature as it enters the cooling
part of the still. Measure the distance from the top of the still head to the takeoff and order your thermometer calibrated over that distance. Some
still heads have a ST built in to accept a thermometer with a ST taper. I have two like this. I prefer the Teflon adapters because they are
adjustable and thermometers without the taper are much easier to get. Plus the same thermometers can be used in certain types of melting point
apparatus.
Arthur Dent - 23-1-2011 at 10:38
Sorry to revive this antique thread, but I have a quick newbie question about thermometers...
I have this old Stansi mercury thermometer (Germany), 30 cm long, with a yellow line background, rated from -20C to 110C, with an eyelet at the end to
hang. Looking at the back, it does have a mark about 2/3 of the way up, right next to the brand name.
That means that when I use the thermometer, I must push it down the rubber stopper so that 2/3 of the body is inside the vessel, right?
It doesn't matter if it's in the liquid or just above it... it just has to be right at that mark on the stopper, correct?
I have been using a digital thermometer ever since i've started my home chemistry endeavors and it's fairly accurate (boiling distilled water at about
102C, hey, I paid ten bucks for it!) but for some experiments where the liquid will be boiling for a long time, I decided to pull out this old
thermomether which I really never used, and I just want to set it up right.
The vessels I'll be using are a 3-neck 250ml boiling flask or a 1L erlenmeyer flask with a 3-hole rubber stopper.
Robert
P.S.: After googling a bit, I learned that Stansi was purchased by Fisher Scientific in 1967, so yeah, it's a vintage thermometer, probably older than
my miserable old carcass... LOL