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UnintentionalChaos
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[*] posted on 29-12-2009 at 08:07


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.




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[*] posted on 29-12-2009 at 11:54


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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[*] posted on 29-12-2009 at 12:08


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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[*] posted on 1-1-2010 at 20:11


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.




So Swiss Miss, she spends her waking hours absolutely focused on being near me, until anything living (other than a human or a plant) enters the picture, at that point she becomes absolutely focused on killing that living thing be it a fly, a kangaroo, a cow, a mouse, it's so otherworldly, she has no sense of herself during these phases, destroying her physical body without pause, or even acknowledgement and she's so quiet about it, very disturbing initially, when you first fully understand this about her.
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[*] posted on 1-1-2010 at 20:52


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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[*] posted on 19-1-2010 at 05:22


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.





So Swiss Miss, she spends her waking hours absolutely focused on being near me, until anything living (other than a human or a plant) enters the picture, at that point she becomes absolutely focused on killing that living thing be it a fly, a kangaroo, a cow, a mouse, it's so otherworldly, she has no sense of herself during these phases, destroying her physical body without pause, or even acknowledgement and she's so quiet about it, very disturbing initially, when you first fully understand this about her.
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[*] posted on 19-1-2010 at 06:37


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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[*] posted on 19-1-2010 at 07:52


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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[*] posted on 19-1-2010 at 07:56


Surly if you are working mildly analytically you must consider the wheight of glassware changes considerably with temperature + humidity...
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[*] posted on 19-1-2010 at 09:55


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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[*] posted on 19-1-2010 at 10:10


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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[*] posted on 19-1-2010 at 11:28


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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[*] posted on 20-1-2010 at 15:23


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]




So Swiss Miss, she spends her waking hours absolutely focused on being near me, until anything living (other than a human or a plant) enters the picture, at that point she becomes absolutely focused on killing that living thing be it a fly, a kangaroo, a cow, a mouse, it's so otherworldly, she has no sense of herself during these phases, destroying her physical body without pause, or even acknowledgement and she's so quiet about it, very disturbing initially, when you first fully understand this about her.
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[*] posted on 20-1-2010 at 18:23


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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[*] posted on 20-1-2010 at 19:36


When you wash the flask doesnt the masking tape come off?!
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[*] posted on 20-1-2010 at 20:39


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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[*] posted on 20-1-2010 at 21:49


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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[*] posted on 20-1-2010 at 22:23


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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[*] posted on 21-1-2010 at 14:58


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 :D)

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.




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[*] posted on 22-1-2010 at 08:24


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 :D)

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 HERE




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[*] posted on 22-1-2010 at 18:56
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.



stir bar retriever.jpg - 62kB

[Edited on 23-1-2010 by Magpie]




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[*] posted on 23-1-2010 at 06:54


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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[*] posted on 23-1-2010 at 09:42


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.




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[*] posted on 23-1-2010 at 20:06


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.




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[*] posted on 23-1-2010 at 20:15


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.




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