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I am planning on doing some distillation in the very near future; however, it has occurred to me that I have had no formal training in proper laboratory distillation techniques.
Since I would very much like to avoid damaging my beautiful new glassware on my first attempt, I figured I would try to do it right the first time rather than having to learn the hard way by trial and error.
My distillation apparatus uses 300 mm Graham condenser, a 1000 mL flat bottom, Florence, boiling flask, and a thermometer adapter built into the connecting tube (all 24/40 ground glass joints), plus a few joint clips.
First of all, when putting it all together, how important is it to add some type of grease or other additional sealant to the joints?
When attempting to distill under reduced pressure (i.e., the inside of the apparatus is at a partial vacuum compared to the surrounding atmosphere), I believe the grease is quite important in order to complete the seal. Also, adding some grease to the joints can help keep them from becoming stuck when trying to remove them afterward.
Is this always a good idea to do? What type of grease is good to use (I assume “Vaseline” won't quite cut it). What about Teflon tape? Could a couple layers of Teflon tape be substituted or used in addition to the grease? Would it work as well?
I have heard somewhere that the Teflon tape might cause extra stress on the joints due to a possible irregularity in the thickness of the layers.
How important is it to use clip to help hold joints together? The safety clips I have are advertised as being safe up to 150° C, I assume beyond this, the difference in the expansion of the clips/glass will cause problems of some sort and put unneeded stress on the glass?
What is the preferred method of heating the boiling flask? Although I have seen claims made that the borosilicate glass is safe for heating by a bare flame, I will not be so stupid as to put this to the test. I had planned on using a [lab] hot plate to heat the liquids, this seems pretty safe, but another method has come to my attention. Using a water bath, one could even more evenly heat the glass as well as provide a much more constant temperature (assuming one doesn’t want to distill at temperatures over 100° C, ideally somewhere a little less than that). One would place the boiling flask in a [metal?] pot of water and let the pot be directly heated by the hot plate. I am less inclined to use oil or sand baths to heat the flask.
Placing some chemically inert, irregularly shaped, objects into the flask would also not be a bad idea either. If I were to get a few pieces of broken glass, for example, and drop them in with the liquid to be distilled, the glass help the liquid boil more evenly rather than “bumping”.
How gradually should the heating process take (and for that matter, the cooling process)? Obviously one does not want to take a flask full of ice water and dunk it into a pre-boiling water bath, but at the same time, this type of glass is meant to be used with heat, so it can take a little abuse (but why put any more stress on it than necessary).
What about the coolant used within the condenser?
The most obvious coolant is air, but sometimes this may not be enough. Water is also another easy to come by coolant. All one would need to do is get a little aquarium/pond pump and some tubing, then one would have a pretty effective way at circulating water within the outer jacket of the condenser. But when distilling at higher temperatures, is using water appropriate? I have heard that at higher temperatures, you suppose to just use air as the coolant, using water would create too much of a temperature difference between the inner and outer sides of the glass. About at what temperature does this become an issue? As is my understanding, the lower the temperature one wants to distill at, the colder one’s coolant is allowed to be (somewhat counter-intuitive in a way).
Due to the replacement cost, I am more than a little bit worried about breaking this stuff, how much of it is justified, how much is me just being paranoid?
Since I would very much like to avoid damaging my beautiful new glassware on my first attempt, I figured I would try to do it right the first time rather than having to learn the hard way by trial and error.
My distillation apparatus uses 300 mm Graham condenser, a 1000 mL flat bottom, Florence, boiling flask, and a thermometer adapter built into the connecting tube (all 24/40 ground glass joints), plus a few joint clips.
First of all, when putting it all together, how important is it to add some type of grease or other additional sealant to the joints?
When attempting to distill under reduced pressure (i.e., the inside of the apparatus is at a partial vacuum compared to the surrounding atmosphere), I believe the grease is quite important in order to complete the seal. Also, adding some grease to the joints can help keep them from becoming stuck when trying to remove them afterward.
Is this always a good idea to do? What type of grease is good to use (I assume “Vaseline” won't quite cut it). What about Teflon tape? Could a couple layers of Teflon tape be substituted or used in addition to the grease? Would it work as well?
I have heard somewhere that the Teflon tape might cause extra stress on the joints due to a possible irregularity in the thickness of the layers.
How important is it to use clip to help hold joints together? The safety clips I have are advertised as being safe up to 150° C, I assume beyond this, the difference in the expansion of the clips/glass will cause problems of some sort and put unneeded stress on the glass?
What is the preferred method of heating the boiling flask? Although I have seen claims made that the borosilicate glass is safe for heating by a bare flame, I will not be so stupid as to put this to the test. I had planned on using a [lab] hot plate to heat the liquids, this seems pretty safe, but another method has come to my attention. Using a water bath, one could even more evenly heat the glass as well as provide a much more constant temperature (assuming one doesn’t want to distill at temperatures over 100° C, ideally somewhere a little less than that). One would place the boiling flask in a [metal?] pot of water and let the pot be directly heated by the hot plate. I am less inclined to use oil or sand baths to heat the flask.
Placing some chemically inert, irregularly shaped, objects into the flask would also not be a bad idea either. If I were to get a few pieces of broken glass, for example, and drop them in with the liquid to be distilled, the glass help the liquid boil more evenly rather than “bumping”.
How gradually should the heating process take (and for that matter, the cooling process)? Obviously one does not want to take a flask full of ice water and dunk it into a pre-boiling water bath, but at the same time, this type of glass is meant to be used with heat, so it can take a little abuse (but why put any more stress on it than necessary).
What about the coolant used within the condenser?
The most obvious coolant is air, but sometimes this may not be enough. Water is also another easy to come by coolant. All one would need to do is get a little aquarium/pond pump and some tubing, then one would have a pretty effective way at circulating water within the outer jacket of the condenser. But when distilling at higher temperatures, is using water appropriate? I have heard that at higher temperatures, you suppose to just use air as the coolant, using water would create too much of a temperature difference between the inner and outer sides of the glass. About at what temperature does this become an issue? As is my understanding, the lower the temperature one wants to distill at, the colder one’s coolant is allowed to be (somewhat counter-intuitive in a way).
Due to the replacement cost, I am more than a little bit worried about breaking this stuff, how much of it is justified, how much is me just being paranoid?