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Panache
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Is that a retort made from an old brick and a piece of rod?
Fantastic!
Here's the photo resized lazy dazy hazy.
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Chainhit222
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Retort? From what I understand a retort is this :
http://upload.wikimedia.org/wikipedia/commons/8/84/My_retort...
Are you referring to my ring stand/lab stand I made out of a rock? I took a leftover stone from wall construction, cut it into a cubic shape using a
rock-saw, drilled a hole in it, filled the hole with epoxy, drilled a hole a tiny bit smaller then the metal rod diameter in the epoxy, and beat the
rod in there with a 10lb dumbbell. I could have just epoxied the rod in there, but I figure this way it is easier to get it to stand up strait.
The other ringstand (round one) was made out of some metal I found in my yard, I drilled a hole in it with a hand drill and used a tap&die set to
make it threaded. I find that I prefer my ringstands to the commercial ringstands (which I find to be too light and easy to tip over).
The thing on the bucket in the back is a condenser pump. I am going to replace it with a nice quiet aquarium pump though.
[Edited on 31-5-2010 by Chainhit222]
The practice of storing bottles of milk or beer in laboratory refrigerators is to be strongly condemned encouraged
-Vogels Textbook of Practical Organic Chemistry
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Panache
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sry meant retort stand not retort, lumps of lead work well as bases also, i agree with you about commercial ones being flimsy and flexible.
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Panache
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filtering cold crystals
Often when one is filtering fine precipitates or crystals from cold solutions one has kept dry it is typical to cover the buchner funnel with a
flexible cover that essentially gets vacuum sucked down ontop of the filter cake, this aids also in compressing the filter cake and speeding the
filtration.
Annoyingly though when one takes the filter cake out as it is very cold it will immediately condense water onto it surface. this is especially true
for fine precipitates. As such it is worthwhile to leave the filtration running until the cake has returned to ambient temperature but this can take
some time and in the interim water can leak into your system anyway.
Using a heat gun ontop of the cake can sometimes work effectively but is also slow as one needs to keep the temperature of the gun just above ambient,
othewise one can volatilise the remaining solvent and problems ensue.
A good trick is to double up a balloon then fill it with enough water to make a sphere around the size of your buchner. This can then be microwaved to
warm it slightly. it is then placed ontop of the filter cake, this gently but quickly warms the cold filtrate in a very controlled manner.
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spong
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If you're distilling something that would usually attack the rubber seals on ordinary thermometer adapters, instead of getting fancy ground glass
thermometers or a teflon adapter, the thermometer can first have one layer of teflon tape wrapped around it, the oring rolled down on top of it and
then another layer of teflon stretched over the top. Then just poke it down into the adapter and thread the cap on top, sealing the teflon against the
glass.
It's also handy for bubbling gasses into flasks, just work out the length for a bit of 6mm boro tube to reach the base of the flask first.
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aonomus
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This thread needs a bump.
In case anyone didn't know, if you find your oil baths stratifying and giving slow heating, bending a paperclip and placing it in the bottom of the
oil bath with a magnetic stirrer is a great way to stir your oil bath, without dedicating a expensive stir bar to the task.
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psychokinetic
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Potentially stupid question time: Are the stir bars often single use?
(I'd put this in the short questions, but it relates directly to your tip.)
[Edited on 29-9-2010 by psychokinetic]
“If Edison had a needle to find in a haystack, he would proceed at once with the diligence of the bee to examine straw after straw until he found
the object of his search.
I was a sorry witness of such doings, knowing that a little theory and calculation would have saved him ninety per cent of his labor.”
-Tesla
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aonomus
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Stir bars are not single use, however sometimes if you leave a stir bar in an oil bath stirring, for ages and ages, when you really want to use it
you will find the teflon worn out and down to the magnet in spots.
Contrary to popular belief, teflon stir bars are not invulnerable to mechanical wear.
Another slight problem is the potential for the heating oil to contaminate future reactions if the stir bar is very pitted, and you have done an
insufficient job at cleaning it; silicon oil is very hard to remove even using hexanes or MTBE. Beyond that, there is all the *other* crud that you
find in oil baths that make it brown/black. I would rather stick my finger into most of my reaction mixtures because I *know* what is in there, vs an
oil bath used by an unknown number of people, with an unknown variety of chemicals.
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psychokinetic
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That makes a lot of sense. I've seen what people do to oil baths.
“If Edison had a needle to find in a haystack, he would proceed at once with the diligence of the bee to examine straw after straw until he found
the object of his search.
I was a sorry witness of such doings, knowing that a little theory and calculation would have saved him ninety per cent of his labor.”
-Tesla
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Panache
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These two photographed products are used for a 'dip' style rubberised coating for tools and the like, whilst very useful for rubberising the handles
of shanks to help you get a good grip whilst murdering inmates they can be used in the displayed style to produce an anti slip 'tread' on concrete or
coated concrete or timber.
I used the 80's random swirl pattern, using black and yellow pants on a matt black pigment and silicon oil coated floor because i'm lazy and it
required little planning, but the results, SPECTACULAR!!!!
Likewise when thinned down a little they are an excellent coating on lab benches, i would have displayed a photo of mine however it just look like a
black bench. I applied it selectively so i have 'zones' without the coating so super hot things can still be placed somewhere.
Also i realised i haven't waffled on yet about my dazzling innovation for uncoated concrete floors, the paving paints made for them are only really
decent if considerable effort in gone into preping the floor, otherwise the coating will readily lift. So you're talking a bout a major effort
mopping, hcl treatment, maybe some grinding, further mopping, removing everything blah blah...However leaving them uncoated means concrete dust,
yucvk!!!
Wow this is sounding like an ad. Anyway if you buy some raw tint from the paint shop, its just staining pigment, the pigment in a minimum of alcoohol,
dilute this down by half and slop it on the floor and brush it around with a broom, trying to get an even coating, or not depending on your laziness,
after this the alcohol quickly dries, like in 2min. You then squirt a minimum quantity silicon oil (from the bath not new stuff!!!) and rub this
around with a broom (not the same one), coating evenly. This effectively coats the pugment (thats NZ for pigment) and the floor, Voila, a surface
treatment for the lab in under ten minutes. it need reapplying now and then, yearly or so.
I use the same treatment for my timber benchtops, using more silicon oil however.
Second tip of the day relates to explaining the dangers of certain chemicals to others. Say if you've explained that NaOH in ethanol/water is very
aggresive to cells even cf NaOH in water as it migrates the caustics readily into the cells, always wear the full gamit of elbow high thick nitrile
gloves, face shield long sleeves, boots blah blah. The tip for others is to never assume that a somber and well intended warning/training, such as
this, will stop someone from being an idiot.
That perhaps harsh, i do feel very badly for someone that i had to sit in emergency with last week whilst their second degree considerable caustically
mangled forearm, wrists and hands where peeled of some of their epidermis and all hair. it was a close call it could have ben so much worse had i used
the concentration of NaOH i would have used. The reality is it's my fault, they were working for me, they got hurt. I considered my training and
supervision more than adequate, bordering on the paranoid, it wasn't.
The problem was all my warnings, training and ernest advice on this chemical was not sufficient for them to infer that if you get it on your skin wash
it off immediately. Their gloves quickly filled with a combination of this cleaner and spray water and the such, but they continued to work because it
didn't hurt, so they thought it must only be water, luckily they had tight nitrile gloves on under the heavy pair of elbow length ones which stopped
the wholesale burning of their hands, forearms and wrists not so, ugly deep red scarring. It makes you feel like a monster when something like this
happens.
Anyway thats it for today.
edit fucked if i know whats up with the photo uploading, probably my wicked photoshops skillzzzzzzz. anyway no photo of te floor sorry. also no spell
checking be3cause i wastede too much tiome trying to get the photo uploaded.
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ScienceHideout
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My tip:
Close the stopcock before you pour something into a sep funnel! It's happened to be a dozen times...
hey, if you are reading this, I can't U2U, but you are always welcome to send me an email!
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Panache
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and it never stops happening IMHO (except it you cease using sep funnels altogether), however the frequency decrease significantly.
A good habit to get into is to make sure you always have a vessel underneath the funnel beorehand, this way you have to forget two things in order for
a problem to occur, which is less likely i find.
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GreenD
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my TA showed me this one;
When running a column, most often people are taught to continuously exchange out test tubes of the filtrates, until TLC analysis shows a change. Often
this is cumbersome to stop, tlc, analyze, etc, so often it is also the case that people run dozens of test tubes, possibly reaching near the hundreds.
Instead of then dotting each test tube on a tlc plate and looking for seperation, simply make a grid on the TLC plate, such that from left to right
and top to bottom is numbered (in your head) 1-n of your #n test tubes. Then simply spot the little squares, one for each test tube, and immidiately
test under UV. This quickly shows which test tubes are completely empty of product and can be ignored, and zeros in on the possible tubes to be
analyzed.
Saves time & plates. Hope that was easy to understand 
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DJF90
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Obviously that method is flawed for a number of reasons. The first is that not all compounds you are trying to separate may be UV active, either at
254nm or 356nm (blacklight). The second is that if one of the fractions contains two compounds (i.e. that either co-elute or are very close Rf values)
then your method will not show the presence of two compounds - you will only see one fluorescent spot. An improved method would be to shine UV on the
fractions themselves whilst still in the test tubes - fluorescence will be noted and you'll save on the TLC plate, but you're still going to suffer
from the same drawbacks.
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GreenD
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I don't think you understood - it isn't a miracle cure for anything, it just saves you the time of making 10 TLC plates for 50 tubes (5 spots on each
plate).
Once you know which one's are active (assuming you know that your compound is UV active), then you continue as usual, eliminating (hopefully) a large
portion of them.
Shining UV on test tubes alone requires complete darkness, and if that is available, then yes - that is probably the better result. However, if your
compound degrades under UV light (short wave) you may want to consider only doing spots.
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Dr.Bob
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A few tips from my experience:
1) A sand bath works very well for heating round bottoms and other items on a hot plate. Put the sand in a metal pot, crystallizing dish or even in
heavy aluminum foil. This works best when you need to heat something at a high temperature for a long time at reflux. Not as good for
distillations or low temps.
2) If you can get one or two long Vigreux columns, it will work well for an air condenser in many cases for refluxing solvents, thus saving water or
other coolants. If you are trying to disconnect Tygon tubing from a condenser, cut it off and slit it. I have broken several inlets off trying to
remove Tygon. To put Tygon on, use a little acetone to swell the tubing for a moment and it will slide right on.
3) When filtering a very wet solid, I was taught to put a thin rubber glove over it and let the suction pull it tight. It will squeeze the liquid
right out of the solids in many cases.
4) To look for non-UV active compounds, take a gram of iodine and place it in 50-100 mls of silica gel in a bottle big enough to hold your TLC plate.
Mix well, and the iodine will saturate the silica. Then place a dry TLC plate in the bottle, turn it until the silica is spread on the plate and
let it sit for a few minutes. This will show spots much faster than just solid iodine in a bottle.
Bob
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ziqquratu
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DJF90, the idea of shining UV light on the tubes directly will rarely work - when we run TLC, the fluorescent compound is pre-bound to the silica
itself (from memory, the most common one is some zinc compound), and the spots we observe under UV light arise through the compounds of interest
QUENCHING that fluorescence. Not many compounds fluoresce themselves when exposed to UV light. You can actually see the difference when you DO have a
fluorescent sample on a TLC plate - rather than the usual dark purple spot, you observe a glowing spot of whatever colour - purple, blue, green, red,
it depends on the compound.
GreenD, your method can be expanded to use stains as well, for compounds which are UV inactive. You can either stain the whole grid once you collect
the number of tubes you expect you'll need, or you can in fact just spot a little of the stain onto each grid square after you spot the sample. It's
not as effective as UV, and the spotting method is almost worthless if you have to heat to see a colour change, but it can work OK for stains like
KMnO4.
The best part about GreenD's method is that you don't have to stuff around preparing a proper TLC plate while running a column. If you're running a
flash column, you need to switch tubes every 30 sec or so. Trying to spot each fraction in that time can be tricky, particularly if you insist on
nice, tight spots. But doing this, you can have big spots - which are quick to do - on your "screening" plate, then go back and just do the fractions
with something in them (plus one or two either side) carefully, saving a lot of effort. Plus, you know immediately when your compound has finished
eluting, meaning you can save time, tubes and solvent.
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DJF90
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I agree that in many cases the indication of product is due to quenching of fluorescence on the plate by the compound - the plate itself is sensitive
to the 254nm light and fluoresces green. Where fluorescence is quenched (i.e. where there is product), the plate appears violet-purple in colour, due
to the longer wavelengths emitted by the bulb. You are right that not many compounds actually fluoresce themselves though, but there are many cases
where this occurs, typically in PAH's. Sometimes a products colour may allow easy identification - compounds with extended pi systems are typical
candidates, such as chromones, which are typically in the yellow region (and azulene (blue), which also shows fluorescence - its actually a special
case in which fluorescence occurs from S2, not S1, due to a conical intersection between the S1 and S0 levels allowing instantaneous relaxation
without emission).
Staining is a good method once UV has been tried, but there are instances where a single stain will not show all the compounds (some common
"universal" stains are p-anisaldehyde, ceric ammonium molybdate and phosphomolybdic acid). If you're only interested in your product, then you may be
able to identify it by a functional group selective stain, depending on what your possible side-products are.
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peach
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Quote: Originally posted by Panache  |
1.Low boiling solvents (dcm, ether, acetone etc) are excellent for their ease of distilling but are a pain for doing vacuum filtrations with as the
solvent can easily boil in the flask, or worse still in the filter. To circumvent this when filtering low boiling solvents i pull a full vacuum on a
round bottom of appropriate size, tap it, then use this a the vacuum source and filter flask. The solvent then has nowhere to go if it boils.
Useful for this technique are some decent taps with groundglass sockets each side. I have a wizz bang 15mm bore, 34/35, vacuum tap i use for this now
but initially i used vacuum tubing, less elegant but completely servicable. |
I've had this problem as well, and found it helpful to first cool the collecting flask in the freezer. With it on super freeze, it'll come out at
about -30C. I wrap in a towel to keep it cool. The solvent attempting to boil in the collecting flask will only cool it further. Provided the flask is
already cold, and insulated, it will quickly run out of energy to boil, if it had enough on entering the flask; which is now effectively a trap it's
laid for it's self.
Conversely, I have had the opposite problem at the filter elements themselves. When dealing with fine particulates and low boiling solvents, the paper
will start clogging a little, then the vacuum below will increase, then the solvent will boil lower and help freeze the funnel some more until the
filtration stops dead. Giving the element a warm with some hot air can make a massive difference to filtration times in these instances; minutes
versus hours.
| Quote: Originally posted by kentkams | | Method is to use some form of vibration attached to your funnel (vibrator or as ive used gamepad vibration motor). |
Yep.
I've done this too.
Another example of where it can help is when dealing with bubbles that sit around the phase boundary in a sep funnel. Putting something that vibrates
against the glass helps them shimmy into place and burst into their own side of the boundary. I thought of this when I found myself tapping on the
side of the funnel with my fingers all the time to knock the lower layer drops that are stuck on the wall in the top layer back down.
It also works to settle some precipitates.
Going back to filtration, one of the best ways to speed it up is to wait for the precipitate to settle by gravity and then remove the top layer first
and only pour in the precipitate as the transfer media (ex solvent) is running out. Sometimes the precipitates clump and sit suspended rather than
falling. A quick buzz with a vibrator of some description and they immediately collapse to the floor.
I have used electric toothbrushes and the Gillette Mach 3 before now, as well as a sex toy. I would recommend the latter as they are variable, more
powerful and soft, so they won't chip the glass. Finding the right spot can take a minute, and it is not always in exactly the same place.
I'll preemptively get in with a, "That's what SHE said!".
[Edited on 17-7-2011 by peach]
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Magpie
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I found that while removing some normally slimy CaSO4 by vacuum filtration the addition of some CaCO3 made the filtration go quite smoothly.
The single most important condition for a successful synthesis is good mixing - Nicodem
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Panache
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Placing an inverted plastic disposable pipette into your wash bottle instead of the tube allows for longer use upside when squirting up into a flask
or whatever, conversely you could have two bottles for each solvent, one with the tube removed and use exclusively upside down.
Obviously the pipette needs to be pierced at the bulb.
[Edited on 6-10-2011 by Panache]
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ScienceHideout
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Don't pipette by mouth.
hey, if you are reading this, I can't U2U, but you are always welcome to send me an email!
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Magpie
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Do you ever get frustrated trying to force the stiff rubber vacuum hose onto the tublature of your Buchner funnel? I often did and was concerned that
I was going to break the tublature and cut myself badly. Here's a convenient solution:
The single most important condition for a successful synthesis is good mixing - Nicodem
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bfesser
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I put some quick disconnects from <a href="http://www.colder.com/" target="_blank">CPC</a> on my rotavap condenser for similar reasons. I
found them for 25¢ a piece at a <a href="http://www.ax-man.com/" target="_blank">local surplus shop</a>, so I bought all they
had.
[Edited on 3/8/12 by bfesser]
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ScienceSquirrel
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Thread Pruned
13-3-2012 at 05:22 |
ScienceSquirrel
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Thread Pruned
13-3-2012 at 05:26 |
Mailinmypocket
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I bought some pipe cleaners to play with my cat... Good times!
I discovered they are the most awesome thing to clean and scrub the inside of droppers, pasteur pipettes, droppers etc! (they are small pipes I
suppose so a pipe cleaner sounds like the obvious choice lol)
They work especially good for removing strong dyes and oily reagents from your small glass and even plastic tubes. Lots of you probably use them all
the time but I just thought I'd share!
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