Thermometer holders and SWITS confusion

thinkpol · Thu Jun 02, 2005 6:24 pm

SWIT is new to this as will soon become clear and has a beckoning question...

SWIT has a 3-necked round bottom flask with ground glass joints and appropriate stoppers. However, he wants to add a thermometer to one of the necks and is confused by the style of adaptor he should be using.

In one hand is

a thermometer pocket. Does this hold the purpose i require it for? Or am i gravely mistaken.

In the other fist is:

a thermometer holder (cone to screwhead adaptor)r. Is this what SWIT needs to hold it in place during reflux?

To conclude, if someone could explain the difference to SWIT between the two he would be greatly appreciative as he feels he has confused himself.

Thankyou for your patience in regard to what is most likely a stupid question

DrugPhreak · Working Bee

I would use the one on the bottom, but does this synthesis specifically call for a thermometer to be placed in one of the joints? If not, just check the temp of the bath... or do you plan on using a mantle?

thinkpol · Thu Jun 02, 2005 9:47 pm

I am using a mantle to heat with. Is this a bad idea:?

thankyou for your help

DrugPhreak · Working Bee

Nah... a mantle is great to have, but I always use an oil bath to keep my costs as low as possible. One bad thing about mantles though... you have to get one for each flask size you plan on using. Since you are using a mantle I guess you'll have to use that thermometer adapter. I would wrap some stringy telfon tape around the thermometer right above the adapter.

Vitriodor · Fri Jun 03, 2005 5:42 am

thinkpol · Sat Jun 04, 2005 10:34 am

Ahh i see.

So what is the first one used for then? Does SWIT need to know dimensions of his thermo when buying the adaptor or is simply joint size enough information.

Thankyou all for your help it has been of much use to SWIT

bio · Working Bee

[quote="thinkpol"].........what is the first one used for then? Does SWIT need to know dimensions of his thermo when buying the adaptor or is simply joint size enough information............................

The thermometer well (pocket) is used to protect the thermometer when inserted thru the neck into the liquid. Use a thermal compound.

Yes, the diameter and length of the thermometer must match the well if you expect to get decent response.This also applies to the other one which is used in a still head to measure vapor. If inserted into liquid it will move and likely break due to turbulence from stirring or vigorous boiling.

Monitoring the oil bath is an option if there is no exotherm or other factors which would cause the reactants to be at a higher temp than the bath and by the time you noticed this it would likely be too late. If you heat very slowly with good stirring the liquid in the flask will be 5deg or so lower than the bath.

The_Dude · Mon Jun 06, 2005 9:02 am

.what is the first one used for then?

The top diagram is used to hold a thermometer immersed in a reaction in order to guage more accurate temperature readings (e.g. a Leuckart reaction).

It is not an essential piece of labware, as the lower thermometer adaptor would also suffice for such a purpose.