Melgar
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Bought a 14/20 glass set for doing small-scale test stuff. Any ideas for what else I'd need?
I just scooped up this set of 14/20 glassware on eBay:
http://www.ebay.com/itm/222270919717
I'd wanted a portable, small-scale glassware set for quite a while now, so I could do test reactions before scaling up more easily, and this seemed to
fit the bill. I'm not really sure what that one three-way stopcock valve is for though. I've also never used a Claisen adapter before, and assume it
would be most useful for distilling with a dropper funnel directly above the starting material, as well as mechanical stirring. Are there other major
reasons to use one? I've never needed to use non-magnetic stirring before, and don't foresee that being something I'd need.
I also got a short-path head, mainly for ease of setting up and cleaning:
http://www.ebay.com/itm/191890322787
Also, just for fast evaporation, it'd be great, since I'll probably be using a brake line bleeder as my vacuum source. Unless someone has a better
suggestion.
My next purchase was going to be from Dr. Bob as soon as he responds to my inquiry, and also, I wanted to get a 9 cm filter funnel, since I could use
unmodified coffee filters with that for stuff that's not particularly important. Of course, a vigreux column and a leibig condenser when I get to the
point where I need it.
My next plan is to characterize and quantify reduction with the aluminum/galinstan alloy I posted about here:
http://www.sciencemadness.org/talk/viewthread.php?tid=70110
So I'm going to try doing the Henry reaction with vanillin and nitromethane and reduce it to an amine and see what my yields are like. Also, I want to
try making aluminum isopropoxide and doing some of the reactions that that reagent makes possible. Also, I want to try doing Pd/C reduction, since
I'm just getting into palladium catalysis, and also because this alloy that I made provides for a really convenient source of hydrogen.
So not having used much jointed glassware outside of vacuum distillation and a buchner funnel, what might I add to this that'd make my life easier?
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Maroboduus
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That was quite a deal. You'll need the condenser soon because how else can you reflux something.
Not Sure if 3-methoxy,4-hydroxyphenylethylamine is scheduled or not. Might want to check on that before you make it, or at least before you tell
people you made it.
Making piperonylamine might be legal since it's an inactive compound.
[Edited on 23-10-2016 by Maroboduus]
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aga
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Jeez.
For me that ebay item is $80 for the stuff, $40 for the postage !
I'll stick with 24/40.
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Melgar
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I usually just keep it at a simmer with magnetic stirring on. It tends to accomplish most of the same things. A vigreux column with the top plugged
with fiberglass keeps virtually all the vapors from escaping, especially if you set up a fan to blow on it. I only use liquid cooling when I
absolutely have to, because it's a lot to set up. There was one other set by that vendor, if anyone's interested:
http://www.ebay.com/itm/14-Pieces-14-20-Lab-Glass-3-Neck-Fla...
If anyone here gets it, maybe we can swap parts that we don't think we'd use?
| Quote: | | Not Sure if 3-methoxy,4-hydroxyphenylethylamine is scheduled or not. Might want to check on that before you make it, or at least before you tell
people you made it. |
It isn't. From my searches of the web, it's a really common one to do as a demonstration, because neither the precursors nor the product are
controlled.
| Quote: | | Making piperonylamine might be legal since it's an inactive compound. |
That's assuming I can get piperonal. Which to be honest, I probably could, but I don't think I'd risk it.
[Edited on 10/23/16 by Melgar]
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Maroboduus
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Good to know that's not controlled.
Sure has cheap precursors.
I can see how it's just about ideal for testing that reaction.
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j_sum1
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Hah! For me it is $80 and $57.
There is a reason I seldom get stuff from the US.
Quote: Originally posted by Melgar  |
| Quote: | | Making piperonylamine might be legal since it's an inactive compound. |
That's assuming I can get piperonal. Which to be honest, I probably could, but I don't think I'd risk it. |
You could make it. Piperine first and then piperinic acid followed by piperonal. Although you probably won't need the last step - just work with the acid.
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Melgar
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I did ozonolysis with black pepper oil to get piperonal once. It smelled like maraschino cherries, but it took forever and I had to keep adding more
solvent, what with running so much air (with a low percentage of ozone) through it. If I wanted piperonal, I'd just buy piperonyl alcohol off of
Alibaba:
http://www.alibaba.com/product-detail/HIGH-QUALITY-piperonyl...
It's used to make a common pesticide, so obviously it's produced by the trainload in China, and most suppliers have a minimum order of 25-100 kg.
Presumably it could be oxidized in similar ways as benzyl alcohol.
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Maroboduus
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A Brake line bleeder sounds like a tough way to do evaporations and such.
If you can afford a an aspirator and pump life will be a lot easier.
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Melgar
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| Quote: Originally posted by Maroboduus | A Brake line bleeder sounds like a tough way to do evaporations and such.
If you can afford a an aspirator and pump life will be a lot easier.
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I don't think I can assume I'm near a drain and a running water source. If an area is zoned residential, then the running water is in the kitchen and
bathroom. If an area is zoned non-residential, often the only running water is in the public restrooms. Sure, I can have a bucket of water on hand
in case things go south, and I can even set up a fume hood in front of the window if I need to, but the necessity of a running water source means I'm
limited from a lot of potential fume hood locations.
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Maroboduus
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You can use a large bucket of water and a water pump. The water will heat up unless you either add ice, or use something large like a trash can, but
it is possible.
Of course, not having a sink makes it less attractive. I've never used a brake bleeder so It may not be as bad as I imagine.
However if you do your chemistry with no water supply around, do yourself a favor and have more than just a bucket of water. (A few gallons in
containers as well at the least).
A bucket of water is the kind of thing that can get knocked over in an emergency. I know that sounds like a string of unpleasant accidents in a cheap
comedy, but it DOES happen. You don't want to be the guy trying to find the nearest bathroom or hose in a chemical emergency. Especially if something
manages to get past your eye protection and your vision is bad.
[Edited on 27-10-2016 by Maroboduus]
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Melgar
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| Quote: Originally posted by Maroboduus | You can use a large bucket of water and a water pump. The water will heat up unless you either add ice, or use something large like a trash can, but
it is possible.
Of course, not having a sink makes it less attractive. I've never used a brake bleeder so It may not be as bad as I imagine |
I was going to use one of these:
http://www.ebay.com/itm/331921072161
Or 2-3 of them in a stack. The hot side can double as an evaporator.
Brake line bleeders aren't so bad for vacuum distillation, since once you establish the vacuum, leakage is minimal. I've ruined a few distilling
nitric acid, but I suppose that's to be expected. I can probably get a small vacuum pump from Harbor Freight if I feel like I need one too.
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Maroboduus
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Damn...
Those things look like they have a LOT of interesting possibilities.
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Melgar
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Peltier junctions are not a very efficient way to cool, since you have to dissipate not just the thermal energy you're extracting, but that generated
by the device. Also, the difference between the hot and cold side has a fixed maximum, which isn't that high, but you can stack them for lower
temperatures. That means having even more waste heat at the hot side though, and if the hot side gets too hot, then the cold side can actually get
hotter than ambient temperatures, because of the fixed temperature difference.
Of course, I'm far more interested in fitting my lab into a toolbox than I am in electrical efficiency. Incidentally, for the cooling water (mixed
with propylene glycol or antifreeze), I plan to stack two of these on the cold side:
http://www.ebay.com/itm/291843839595
The top one would be for coolant going out, to make it colder than the tank, and the bottom one would be for return coolant, to cool it off before it
can mix with the rest of the coolant. Then I'd probably stick an old aluminum heat sink on the bottom of that.
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Sulaiman
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Some quick calculations for 'ballpark' figures using water,
heat of vaporization 40.65 kJ/mol or 2257 kJ/kg.
At 500 ml liquid evaporated and condensed per hour,
(or 50 ml/hour product with 9:1 reflux ratio)
heating power = cooling power = 315 Watts (minimum)
Your condensing power will always be about the same as your heating power.
P.S. Melgar, I think that a pressure-equalising funnel would be a useful addition to the kit.
A 7/15 thermometer, or thermocouple pocket would be nice, with a 7/15 to 14/20 adapter.
and for vacuum, a 'pig' or similar seems essential.
[Edited on 27-10-2016 by Sulaiman]
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Maroboduus
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@Melgar
Yeah, I was thinking of using them for condenser coolant too. I often just use a large container of water and a pump and add ice (Or blue ice packs)
if the water heats up too much. With these cooling the water before it enters the condenser I could let the water in the container get warmer and
still have the same temp for the condenser feed. Then the water tank would dissipate more heat from convection and evaporation and I'd need less ice
(maybe none). Seems I'm always running short of ice on warm days.
Also a cold plate for convenience when working with low boiling solvents.
I had no idea Peltier junctions and heat exchangers could be had so cheap.
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Melgar
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| Quote: Originally posted by Sulaiman | Some quick calculations for 'ballpark' figures using water,
heat of vaporization 40.65 kJ/mol or 2257 kJ/kg.
At 500 ml liquid evaporated and condensed per hour,
(or 50 ml/hour product with 9:1 reflux ratio)
heating power = cooling power = 315 Watts (minimum)
Your condensing power will always be about the same as your heating power. |
I'd expect it to be substantially less, as long as the apparatus isn't insulated. Lots more heat is lost to the atmosphere on the heating side that
absorbed from the atmosphere on the cold side, especially with a vigreux column with a fan pointed on it. On the other hand, heating is nearly 100%
efficient, while cooling is not. Though, if you use enough Peltier junctions, you could possibly make them pump heat directly from the coolant into
the fluid, and your atmospheric heat sink would be your vigreux column. And really, with a setup this size, two of these junctions would probably be
enough. I bought five of them anyway, since I don't know if or how easily these things burn out, and I'd rather put down ten bucks to have some
spares than have to wait two weeks for replacements.
| Quote: | | P.S. Melgar, I think that a pressure-equalising funnel would be a useful addition to the kit. |
And what do you know, a member just offered a 14/20 set that included one for a really good price. 
| Quote: | A 7/15 thermometer, or thermocouple pocket would be nice, with a 7/15 to 14/20 adapter.
and for vacuum, a 'pig' or similar seems essential.
[Edited on 27-10-2016 by Sulaiman] |
Is this what you mean by "pig"? It seems like it would make a sort of grunting noise while it was running:
http://www.ebay.com/itm/311057103383
[Edited on 10/29/16 by Melgar]
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Maroboduus
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A 'Pig' is another name for a 'cow' A receiver that has connections for 3 or 4 flasks that can be rotated so each flack can collect a fraction
without having to break vacuum to change flasks.
The name cow comes from some of them looking like udders. Don't know why they also call them pigs.
I have one of those pumps in your link. Mine pulls nowhere near the vacuum they claim. Seems to not have the torque it needs as it stalls out. Maybe
because I just hooked it to a hose and gauge. I probably out to try it out again evacuating a flask....
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Sulaiman
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I too use one of those pumps, at least -75 kpa gauge, runs for hours,
it is under powered for restarting with a vacuum.
but
I meant 'cow' or 'pig' like this http://www.scilabware.com/Adapters/Receiver/Pig-receiver/p-1...
almost impossible to collect just the fraction that you want
for a vacuum fractional distillation without something similar
My rotary vacuum pump needs more 'plumbing; so I've only used moderate vacuum so far, but it immediateky becomes clear that a cow/pig is required.
Even if just to keep the system sealed for extraction of 'nasty' gasses it is a useful accessory/component.
I think I've just talked myself into ordering one 
P.S. an air condenser, or a column with a fan etc. is still cooling power, just in a different place
[Edited on 29-10-2016 by Sulaiman]
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Melgar
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| Quote: Originally posted by Maroboduus | I have one of those pumps in your link. Mine pulls nowhere near the vacuum they claim. Seems to not have the torque it needs as it stalls out. Maybe
because I just hooked it to a hose and gauge. I probably out to try it out again evacuating a flask....
|
I wonder how hard it would be to install some sort of manual transmission? Once it starts straining, flip it into geared mode. Or just have two
pumps, one geared and the other not. That way, I could have the geared pump holding a vacuum, with the other pump doing vacuum filtration or
evaporation. Or I could just replace the motor. I find discarded laser printers all the time, and the motor in the last one I took apart seems like
it'd be stronger than this one.
Edit: is it easy to rotate one of those things in a ground glass joint under vacuum? I guess it'd have to be, but you'd probably need to use proper
silicone grease and not a mixture of wax and petroleum jelly like I've been using.
I just HAD to get the cheaper silicone grease, despite the 20-day shipping estimation...
[Edited on 10/29/16 by Melgar]
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Maroboduus
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@Sulaiman, nice to know they work okay when set up right. I'll have to give it another try. Hooking it right to a short hose and gauge was probably my
problem.
The pump assembly is just held on with screws, so I'd wondered about taking it off and putting it back on with the thing through a hole in a small
strong airtight box so the motor is on the outside where it can cool, but the pump is in a chamber that can be evacuated with another pump or an
aspirator.
Piston leakage, and torque requirements would be reduced by the low pressure atmosphere and it might be able to function as a booster that way for
another of the same pumps. Get down to 75 mm of mercury or less and you're starting to be able to use it for a lot more stuff.
I wonder if it might not even be able to cut the pressure you get with an aspirator in half with one as well.
You couldn't separate the pump assembly and motor by much without making it pretty hard on the bearings, but say a 1/16 inch piece of steel sheet and
that is attached to a slightly larger hole in a more robust box (say 3/8 or 1/2 inch plexiglass).
I know vapors would need to be dealt with. Wonder what kind of plastic it is. I must check. Might be able to handle alcohols at least.
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Sulaiman
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| Quote: Originally posted by Maroboduus | @Sulaiman, nice to know they work okay when set up right. I'll have to give it another try. Hooking it right to a short hose and gauge was probably my
problem.
The pump assembly is just held on with screws, so I'd wondered about taking it off and putting it back on with the thing through a hole in a small
strong airtight box so the motor is on the outside where it can cool, but the pump is in a chamber that can be evacuated with another pump or an
aspirator.
Piston leakage, and torque requirements would be reduced by the low pressure atmosphere and it might be able to function as a booster that way for
another of the same pumps. Get down to 75 mm of mercury or less and you're starting to be able to use it for a lot more stuff.
I wonder if it might not even be able to cut the pressure you get with an aspirator in half with one as well.
You couldn't separate the pump assembly and motor by much without making it pretty hard on the bearings, but say a 1/16 inch piece of steel sheet and
that is attached to a slightly larger hole in a more robust box (say 3/8 or 1/2 inch plexiglass).
I know vapors would need to be dealt with. Wonder what kind of plastic it is. I must check. Might be able to handle alcohols at least.
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There is the body which seems to be POM or nylon, a black rubber sliding seal, and silicone rubber flappy valves.
The weak point is the end of the crank shaft that fits onto the motor pinion.
I know this because I bought two, and tried using them in tandem to get a better vacuum ...
now I have one pump and some spare parts
Although it is quite a good vacuum pump,
a brand new oil sealed rotary vane hvac vacuum pump is only 4x the price
e.g. http://www.ebay.co.uk/itm/New-2-5CFM-1-4HP-Single-Stage-Rota...
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Melgar
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I just picked up a hand-operated brake line bleeder at Harbor Freight for $25, and that thing can just about pull a full vacuum according to the
pressure gauge on it. It even has a cup that can work as a trap for your vapors so they don't reach your suction mechanism. (You'd have to put the
correct fluid in it to trap the vapors you expect to get, of course; NaOH + peroxide for distilling nitric acid, aqueous sodium thiosulfate for
reactions that generate halogens, etc.) Combine that with a check valve to prevent suck-back, and it wouldn't take more than a minute to evacuate a
14/20 distillation setup. I know I've pulled enough of a vacuum with one of those things to make it so that bumping would shake the whole apparatus
to the point where it seemed like it was going to fall apart, even with boiling chips. So having a really high vacuum isn't always ideal. For lots
of things, the hand-operated pumps are a lot more convenient, because you have a lot more control over the pressure, and you don't have to set up an
electrical connection every time you want to use it.
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Sulaiman
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That sounds like a useful pump for vacuum filtration and distillation,
especially the easy control of distillation pressure.
So far I have only tried reduced pressure distillation (-75 to -80 kPa gauge)
Proper vacuum distillation is beyond me at the moment
due to the very low temperatures generally required for condensation.
Control of the vacuum level when using my rotary is mainly what I meant by 'plumbing',
Not many liquids stay liquid at full vacuum (<1 Pa).
The other part is making vapour 'traps'.
When you consider the cost, inconvenience and 'breakability' of vapour traps for vacuum pumps,
$25 is almost 'disposable'
But I would love to see you trying to pull air through filter cakes to dry them with that little hand pump
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Melgar
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| Quote: Originally posted by Sulaiman | That sounds like a useful pump for vacuum filtration and distillation,
especially the easy control of distillation pressure.
So far I have only tried reduced pressure distillation (-75 to -80 kPa gauge)
Proper vacuum distillation is beyond me at the moment
due to the very low temperatures generally required for condensation.
Control of the vacuum level when using my rotary is mainly what I meant by 'plumbing',
Not many liquids stay liquid at full vacuum (<1 Pa).
The other part is making vapour 'traps'.
When you consider the cost, inconvenience and 'breakability' of vapour traps for vacuum pumps,
$25 is almost 'disposable'
But I would love to see you trying to pull air through filter cakes to dry them with that little hand pump |
Oh, I have before, plenty of times. Sometimes the liquid would drip through and immediately sublimate. As long as there aren't any leaks, pulling a
near-total vacuum is easy. You then just have to wait for enough liquid to come through for the pressure to change appreciably. With a 500 mL filter
flask, you can do that, say, once every ten minutes while you go do other stuff. In terms of effort, it's only about as hard as inflating the tires
of a bike.
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Sulaiman
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Perkin Triangle
I should add:
If more than three fractions are expected for a vacuum fractional distillation
then a Perkin triangle would be better but costlier.
e.g. (copied from a live eBay listing)
Just use in place of a normal receiver/adapter.
Just to cover myself agaist complaints of inappropriate recommendation of cows/pigs 
[Edited on 2-11-2016 by Sulaiman]
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