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UnintentionalChaos
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Quote: Originally posted by aonomus  | | Another thing with gallium is that it wets glass unlike mercury, wouldn't that make it a pain to clean off? |
I believe the reactivity is similar to tin. Stong HCl should remove any residue in a hurry.
Department of Redundancy Department - Now with paperwork!
'In organic synthesis, we call decomposition products "crap", however this is not a IUPAC approved nomenclature.' -Nicodem
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User
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Another trick popped to mind.
Sometimes it does happen that one spills something like strong acid, base or whatever.
Cleaning can be messy and a quite unpleasant experience.
there is a very easy and cheap solution to the problem.
Use kitty litter!
This material (often made out of bentonite) is very absorbent and can suck up an amazing amount of liquid which afterwards can be disposed with great
easiness.
The cheapest brands often contain the least "contaminations" and proven to work best imo.
There actually is a professional alternative on the market,
but this is way cheaper and came out as a brilliant solution a couple of times.
For the ones that did not know this I hope you like it.
What a fine day for chemistry this is.
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aonomus
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Another trick that I've been using recently is using a claisen adapter with 2 gas inlet adapters fitted to a large RBF to do filling operations.
Essentially, pull vacuum on the higher one, and use a tube to siphon liquid from a large container until the flask is full to the level you want. Much
safer than attempting to lift buckets high and risk getting stuff spilled.
Only catch is that your tubing limits what you can use this with.
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Panache
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If you have a dead hard drive, open it and get out the rare earth magnet (providing the HD is circa this century). This makes a great tool for
holding magnetic stirrer beads fast onto the bottom of your flask when pouring or transferring its contents.
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aonomus
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So I saw at Walmart a few days ago a medium sized glass cookie jar. Likely not pyrex, and definitely not strong enough to withstand vacuum, but for a
plain old desiccator, it would work great. Just need to add a separator to allow beakers to sit above the desiccant. Its taller than the small
lock&lock container, and would let me place larger beakers inside.
As for the hard drive magnet (and other magnets), I have realized that the sudden increase in force when you bring the magnets together is sometimes
enough to pinch fingers and maybe even scratch or chip the glass. I want to coat my magnet in plastidip, but can't justify buying it (its somewhat
pricey) for only 1 project. A cheap substitute are a few layers of paper towel that help cushion the forces.
Oh, and a word of warning for anyone that wants to add copper metal mesh (from copper pot scrubbers) to a hempel column to scrub any sulfur compounds
from the vapors: its not pure copper, its copper plated steel, and thus, rusts.
Edit: Another word of warning - clear PVC tubing at 0degC is a bad thing. I use tygon tubing in the entire coolant loop except for 2 short stubs of
PVC that connect the glass tubing connectors to some plastic quick disconnects. To my horror I discovered that the tubing had become rock hard, so
hopefully no flexing occurs allowing it to crack.
[Edited on 2-1-2010 by aonomus]
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Panache
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| Quote: Originally posted by aonomus |
As for the hard drive magnet (and other magnets), I have realized that the sudden increase in force when you bring the magnets together is sometimes
enough to pinch fingers and maybe even scratch or chip the glass. I want to coat my magnet in plastidip, but can't justify buying it (its somewhat
pricey) for only 1 project. A cheap substitute are a few layers of paper towel that help cushion the forces.
[Edited on 2-1-2010 by aonomus] |
Wrap it around several times with polyethylene film (aka that stuff you wrap your sandwiches in) then either flame it shut or oven, its now spongy and
durable!
Of course your could just gently place the magnet on the glass.
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aonomus
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Good strong rare earth magnets sometimes jump, despite trying to place them gently on the glass....
So anyway, I've discovered by chance, that certain sizes of PVC plastic pipe caps make good cheap substitutes for cork rings in a pinch, especially
for larger flasks that you wouldn't ordinarily have a ring for. A little bit of tape or rubber tubing around the edge helps make it softer and less
slippery to the glass.
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bbartlog
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I found it convenient to label most of the glassware (and some other items) in my lab with their weight in grams, and also record the weight of some
items that are too small to label. I work almost entirely by weight rather than volume, and this makes it a lot easier to determine the weight of
beaker or flask contents without needing to transfer contents or even remove stoppers.
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Picric-A
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Surly if you are working mildly analytically you must consider the wheight of glassware changes considerably with temperature + humidity...
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woelen
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Hmm... weight of glassware changing with temperature? I don't think so. Density may change slightly, but total weight definitely not. Humidity also
does not affect the total weight of glassware, unless the air is so humid that droplets of water condense on the glassware, but if that occurs, then
it is time to look for another room for experimenting 
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bbartlog
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I'm sure there is some adsorption of water on glass (else why bake it beforehand when making an anhydrous setup), but I don't think it's enough to
matter to me. If I worked at the microscale instead of with quantities on the order of 100g it might be important.
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Picric-A
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| Quote: Originally posted by woelen | | Hmm... weight of glassware changing with temperature? I don't think so. Density may change slightly, but total weight definitely not. Humidity also
does not affect the total weight of glassware, unless the air is so humid that droplets of water condense on the glassware, but if that occurs, then
it is time to look for another room for experimenting |
The temp determines the amount of water absorbed by the glassware, as temperature changes humidity.
And i am sure humity changes wheight of glassware, if not one would not have to bake it before use + dont forget glass is just a less hydroscopic
version of silica gel, with varioius other compounds in there.
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Panache
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| Quote: Originally posted by bbartlog | | I found it convenient to label most of the glassware (and some other items) in my lab with their weight in grams, and also record the weight of some
items that are too small to label. I work almost entirely by weight rather than volume, and this makes it a lot easier to determine the weight of
beaker or flask contents without needing to transfer contents or even remove stoppers. |
How do you label it though that is impervious to all the conditions it must withstand? engraving works but then you introduce possible stress
fractures that cracks can apex off.
[Edited on 20-1-2010 by Panache]
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bbartlog
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I've had to replace scorched tape occasionally, but masking tape and permanent marker (Sharpie) works pretty well for me; good up to about 200C at
which point it starts to darken. I suppose some solvents would also wipe it out or disintegrate the adhesive, but I haven't experienced that yet. I
suppose if you did a lot of work at higher temperatures that wouldn't be satisfactory, but so far the vast majority of what I've done has involved
temps between -10C and ~230C (at least on the upper outside parts of the glass).
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DJF90
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When you wash the flask doesnt the masking tape come off?!
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bbartlog
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Interestingly, no. The adhesive on the masking tape sticks to glass quite well. Maybe if I ran my glassware through a dishwasher?
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aonomus
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I have found that masking tape on glass bottles and the like stick *very* well, even if you get a bit of solvent on them. The marker might run, but
the solvent only loosens the adhesion briefly until it dries out again. You have to soak the tape in solvent and scrape, then use a acetone soaked
paper towel to remove all traces of the adhesive if its really old and baked on.
In some other cases, the adhesive does dry out and the tape flakes off, but then that is a different issue.
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DJF90
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I would have never have guessed! Sharpies are good for temporary annotation of flasks (crude yield, molecular structure (if its to be left on the
shelf for some time...) etc. Some flasks (particularly pyrex/duran) have a small white enamel square, which when marked with a pen is very difficult
to remove. This could be ideal for recording the weight of your flasks, at least long term if not permanently.
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vulture
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Pencil inside a ground glass joint or on the outside in the white painted square of a piece of glassware holds up to almost anything, except vacuum
grease and chromic acid.
Grignards are best initiated by using 1,2-dibromoethane, IMHO.
I have another tip for catalytic hydrogenations with Pd/C. This is often done with a parr apparatus connected to a variation of a Schlenk line, to
evacuate the setup and refill with hydrogen. This is done because the H2 can be explosive in combination with Pd and O2. (Usually happens in the
student lab sessions  )
For hydrogenations that don't require large overpressures, I simply use a flask with a magnetic stirrer connected to a three way valve. The other two
outlets are connected to a balloon filled with N2 and a water aspirator (or vacuum pump). This allows to remove all oxygen from the setup first by
switching between the aspirator and the N2. Once the balloon is drained, it's switched for one with the H2 and the evacuation/purging cycle is
repeated. Finally, the vacuum source is disconnected and another balloon of H2 can be connected if necessary.
When reducing small quantities you can dispense of the N2 and go straight to H2. Take care that the flask is filled to no more than 1/3 of it's
volume, because of the boiling that can occur during application of the vacuum.
One shouldn't accept or resort to the mutilation of science to appease the mentally impaired.
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medchem
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| Quote: Originally posted by vulture | Pencil inside a ground glass joint or on the outside in the white painted square of a piece of glassware holds up to almost anything, except vacuum
grease and chromic acid.
Grignards are best initiated by using 1,2-dibromoethane, IMHO.
I have another tip for catalytic hydrogenations with Pd/C. This is often done with a parr apparatus connected to a variation of a Schlenk line, to
evacuate the setup and refill with hydrogen. This is done because the H2 can be explosive in combination with Pd and O2. (Usually happens in the
student lab sessions )
For hydrogenations that don't require large overpressures, I simply use a flask with a magnetic stirrer connected to a three way valve. The other two
outlets are connected to a balloon filled with N2 and a water aspirator (or vacuum pump). This allows to remove all oxygen from the setup first by
switching between the aspirator and the N2. Once the balloon is drained, it's switched for one with the H2 and the evacuation/purging cycle is
repeated. Finally, the vacuum source is disconnected and another balloon of H2 can be connected if necessary.
When reducing small quantities you can dispense of the N2 and go straight to H2. Take care that the flask is filled to no more than 1/3 of it's
volume, because of the boiling that can occur during application of the vacuum. |
Few months back, I have written a post regarding this procedure with video ...
Check out in detail <a href="http://medchemblog.blogspot.com/2009/11/hydrogenation-demonstration.html">HERE</a>
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Magpie
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stir bar retriever
Finding that I often wish I had one of these but am not willing to pay the $20 + postage, I made one of my own. Here's how:
* Buy 2 feet of 0.17"ID polyethylene tubing ($0.34)
* Buy one 3 foot piece of 1/16" steel rod (~$2)
* Buy one 3/16"OD x 1/2" long cylindrical neodymium magnet ($0.27) (Note 1)
1.Heat about 3/4" of one end of an 18" piece of poly tubing in boiling water to soften it, then force fit the magnet into it, leaving about 1/4" of
the end of the tube open.
2. Fuse this end of the poly tube by heating it on a stove, working the end to a seal. Try not to overly heat the magnet as it will lose its
magnetism if heated to 80C. (Note 2.)
3. Cut the steel rod to fit in the poly tube leaving about 1/2" of the tube end open.
4. Fuse the open end of the poly tube as before.
Notes
1. The economics are hurt here if you have to pay postage on the magnet like I did. This came to about $5.
2. It might be better to buy an undersize magnet, say 1/8"OD instead. That way you could slide the magnet in later after fusing the end to a seal,
and wouldn't have to risk heating the magnet. These Nd magnets are tremendously strong.
[Edited on 23-1-2010 by Magpie]
The single most important condition for a successful synthesis is good mixing - Nicodem
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watson.fawkes
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| Quote: Originally posted by Magpie | | 2. Fuse this end of the poly tube by heating it on a stove, working the end to a seal. Try not to overly heat the magnet as it will lose its
magnetism if heated to 80C. |
If you do accidentally heat the magnet above its Curie point, you can
remagnetize it by heating it up again and letting it cool off in a magnetic field. A ferromagnet is randomly aligned above its Curie point and an
external magnetic field will line them up. As it cools and passes through the Curie point, the magnetic domains lock into place in whatever their
alignment is. The strength of the external field doesn't need to be as strong as the magnet itself. The final strength of the magnet is dependent upon
its own material properties. All the external field has to do is to get the domains lined up right.
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Magpie
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Thank you watson for that useful information. My heating did cause the magnet to lose much of its strength, although as you can see from the photo,
its still plenty strong enough for its intended purpose. At full strength these tiny magnets are supposedly capable of lifting ~1 kg, IIRC.
I did buy a second slightly larger magnet. Are you saying that if I heat the magnet in the retriever up to 80C then let it cool next to this second
magnet that I can remagnetize the one in the retriever? Is any special spatial orientation needed? They are both 3/16"OD cylinders. The strong one
is 3/4" long.
The single most important condition for a successful synthesis is good mixing - Nicodem
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mr.crow
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Perhaps you could push the magnet further into the tube, seal it then push it back to the end with a coat hanger.
Stirbars are also magnetic, perhaps an iron nail would also work.
Double, double toil and trouble; Fire burn, and caldron bubble
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Magpie
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| Quote: Originally posted by mr.crow | Perhaps you could push the magnet further into the tube, seal it then push it back to the end with a coat hanger.
Stirbars are also magnetic, perhaps an iron nail would also work. |
For the 3/16" magnets I bought they are way too tight for that.
I tried to just use the steel rod end out of curiosity, but it didn't provide enough attraction.
The single most important condition for a successful synthesis is good mixing - Nicodem
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