LuckyWinner
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Automatic Addition of Liquids and Solids into Flasks?
Im trying to find out the best ways to transfer liquids and solids fully automatically from
reagent bottles into the reaction vessel.
(microcontrollers, stepper motors and a few lines of code)
you could use...
Liquids
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[1] peristaltic pump
Negative - Can't pump 'strong' chemicals, otherwise tubing gets attacked
- Hard to dose accurately
[2] syringe pump
can pump any liquid if its connected with ptfe compression fittings and teflon tubing.
can be a DIY pump with stepper motor.
can be dosed accurately.
[3] create pressure inside a bottle, by having
3 tubes inserted into reagent bottles.
tube 1 creates pressure
tube 2 is the chemical transfer tube which leads into the reaction chamber
tube 3 pressure release
CON - hard to dose / overshoot possible if pressure to high (siphon) / many failure possibilities
how would one accurately calculate the grams of liquid that the pumps output into the
reaction vessel without overshoot?
use a hanging scale which holds an intermediary 'scale' flask.
the pump will stop once x grams are hanging down the scale.
Powders
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whats the best way to transfer and weight powders?
there are POWDER ADDITION FUNNELS but how can you calculate the powder
that is being added?
any simple solutions for this?
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itsallgoodjames
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Why don't you dissolve the powder in a solvent? That'd make the automatic addition of a specific amount much easier
Edit- sidenote, why is this in reagents and apparatus acquisition, rather than miscellaneous?
[Edited on 12-3-2021 by itsallgoodjames]
Nuclear physics is neat. It's a shame it's so regulated...
Now that I think about it, that's probably a good thing. Still annoying though.
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LuckyWinner
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I thought about that too... there may be a suitable solvent...
anyhow how would one accurately determine the liquid volume/grams that is getting dispensed
by one of the listed methods?
an intermediary 'scale' flask that is hanging on ropes attached to a hanging scale?
how do professional labs do this?
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itsallgoodjames
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Quote: Originally posted by LuckyWinner  |
I thought about that too... there may be a suitable solvent...
anyhow how would one accurately determine the liquid volume/grams that is getting dispensed
by one of the listed methods?
an intermediary 'scale' flask that is hanging on ropes attached to a hanging scale?
how do professional labs do this? |
I should note that I have no clue how professional labs do it, but I can tell you how I would do it with the peristaltic pump.
What you could do is fill the pump with water, put the inlet in a bucket of it and the outlet in a grad cylinder. Then run the stepper motor through
say 100 steps. Measure the amount of water in the grad cylinder. Divide by 100. You now have the number of ml of water per step of the stepper
motor.
Nuclear physics is neat. It's a shame it's so regulated...
Now that I think about it, that's probably a good thing. Still annoying though.
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Belowzero
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Not sure what these devices are called but I've seen powder addition devices.
Basically a tube with a spiral drill like cilinder in it that rotates and adds solids this way.
Reminds me of those garden drills.
https://m.media-amazon.com/images/S/aplus-seller-content-ima...
[Edited on 12-3-2021 by Belowzero]
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Fyndium
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Liquids: dropper funnel. Nuff said.
Solids: if you got the funds, a powder funnel. Otherwise you could try to improvise a screw conveyor. For the last, add manually. I just did it by
finding a scoop that had a proper volume for powder addition, and scooped it in over a time. I must admit, if this could be automatized, I would be
willing to invest a little for it, babysitting a reaction like that is very boring.
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LuckyWinner
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there are a few youtube videos.
you could add a stepper motor to the glass powder addition funnel valve.
but
1. how to calculate the powder in grams that was added?
use 2 of these powder feeders, with 1 intermediary scale unit?
2.the powder adder will be directly attached to the top of the reaction vessel.
I want to have a valve between the powder adder and reaction vessel.
I am not aware of any 'wide mouth' valves where the powder will fall through
24/40 usually only has these narrow neck valves... powder will probably get stuck...
maybe make a custom stainless steel valve with teflon thread 24/40?
sounds complicated any simple solutions?
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Fyndium
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Reloading devices have a very accurate volume-based dosing mechanism that is used to fill the gunpowder charge. Possibly this sort of mechanism could
be used. Powder is in the form of small granules though, so they are more free flowing than any untreated bulk powder without anti-caking agents.
I know for a fact that powder will eventually clog 24* joint very quickly, I have experience from it no more than 3 days ago when I did my last
reaction that involved powder addition and I had to poke the joint with stir rod many times to push the powder clog and all the powder adhered to the
walls.
Powder measuring needs repeatability. I did ten tests by just casually scooping power with my scoop and the average powder amount collected was
between 3.5 and 4 grams every time, so any device with constant mechanisms will work if you just fit the size for your needs. A screw conveyor will
move approximately the same amount by every turn. Don't really care the precise amount per scoop, because the pot I scooped the powder contained 100%
of the powder required for the reaction, so eventually all of it will be added.
Any automatic mechanism will be likely very complicated and expensive to do, especially compared to more rudimentary methods. Stepper motors aren't
quite expensive nowadays, but other things like clogging valves and other stuff will make things much more complicated.
[Edited on 12-3-2021 by Fyndium]
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LuckyWinner
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what about 3D printing your own screw conveyor belt.
powder is getting filled into reagent bottle.
bottom of bottle has an outgoing tunnel which houses a feeding
screw which is mounted to a stepper motor.
powder output is landing on a little platform with a sidearm connected
to a load cell (a scale).
once X grams of powder is added, the platform will tilt 180 degrees
into a new screw conveyor belt which leads into the reaction vessel at
x speed of stepper motor.
the last conveyor belt is attached to a stainless steel widemouth ballvalve stepper motor controlled teflon adapter which rests on the top of the
flask.
this allows to protect the chamber from the reaction vessel once addition is finished.
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Fyndium
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Meh, just use single screw. Measure the rotation and output, if you turn it 90, 180, 360deg etc and how much powder comes through. Put stepper to it
and program it to make specific turn in time intervals.
Remember, keep it simple. As simple as possible. Less probability of error, and only make it more complex if it is beneficial and makes it more
reliable. For example, another vertical screw that is on constant slow rotation would prevent clogging the powder feed chute.
Also remember that ordinary 3D printing materials like PLA, ABS, PS and those will basically melt with all common solvents, so you need to invest into
chemical resistant material first, for example nylon, or even better, PE/PP.
It is likely you would be able to use many otc parts for the device, for example wood drill bits can be used as an auger screw, just find a piece of
pipe that it neatly fits in and 3D print a mount for stepper and add a powder funnel and feed adapter into ground joint. These can be turned from PTFE
stock if necessary.
[Edited on 12-3-2021 by Fyndium]
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zed
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Possible in limited ways. Were the craft perfected, perhaps Elizabeth Holmes would still be a tech-giant, rather than an indictee for fraud. Folks
banked billions, on building small automated machines, for performing chemical tests on blood.. It proved less feasible than it sounded.
https://en.wikipedia.org/wiki/Theranos
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Fyndium
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Funny, I remember seeing headlines on our national newspaper praising her like a god. A few years later, only crickets were chirping. To be honest,
I've been wishing instant home blood sampling for years.
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Dr.Bob
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As a "professional" chemist who used a lot of automation at my previous job, I will chime in.
Liquids, simplest way is addition funnels, they can clog (happens to me all of the time), they can change speed of addition as the liquid volume
changes the pressure), and they can even leak if the stopcock is not right. But that is still what most people in research use after many years of
trying to find better answers.
The next best way is a syringe pump, especially for highly reactive compounds, small amounts, or times when the rate is critical. They are
expensive, prone to issues (slippage, leaks, picking the wrong setting/rate, and more). You also then need either a long needle or some way to hold
the pump over the septa where the needle goes in. But they are still used a fair bit in real life research.
Lasltly, pumps and pressure driven systems. these work best for solvents, other large amounts, and when the rate of addition is not critical. FMI
pumps are in between peristallic pumps and syringe pumps, in that they can handle many harsh solvents, and are pretty accurate and controllable, but
even they can clog or jamb, just happened to me yesterday tryign to load a solution that contained some fine solids, so I had to go back to a large
plastic syringe and make multiple additions with it manually.
As for solids, even worse. I have used many solid addition auger type funnels. But they work best on large amounts of solids, with fine,
consistent particle size. The solids must be free flowing, anything that gets sticky or clumps is bad (think EDC, CDI, AlCl3, sodium
triacetoxyborohydride, etc). What most real chemists do is add them in portions if they cannot be dissolved (if you could dissolve it, you would not
bother trying to add a solid). I just rain another large scale reactioon recently, and it requires the addition of the catalyst in portions. The
ideal world would add it a little at a time, but I have found that putting 1/4 of it in at a time is OK, and since it is nearly insoluble and air and
light seneitive, that works better than trying to find anothe way. Even in larger scale pilot plants, solids are often added in small portions,
manually quite often, as most automated ways just are not reliable enough.
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Fyndium
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So any pop-up type systems might not be very reliable or economically viable, especially for the amateur.
But what kind of systems they use in production industry? Conveyor belts? Augers? Apparently as the scale goes up, the clumping and other things
become easier to manage. At least one benefit of auger is that it can be driven with huge torque by using worm gear, so even more resistant masses can
be simply pushed along. As far as I know, auger type feed is used for plastic molding where pressures up to 200bar are used.
I would see a potential for making a mini auger funnel for adding powders into reactions in hobby scale. Only downside is that one will likely need
access to a lathe, a mill and preferably to a welding machine to cut many corners that would take hours of extra work to machine. The structure would
be very simple: a tube, which into an auger is fitted, as I said, in this instance one could very likely be made from wood drill, and bushings could
be made from HDPE/PTFE, and a simple worm and spur would be added and a mount for the stepper to turn it. A funnel would be installed on top of the
tube, and the end would fit a feed chute that can be fitted to ground joint, 24* minimum. Simple test run to find out how many degrees the stepper
must turn to feed a desired amount would be easy to carry out.
Btw, I just ran into uniform powder issue with my last reaction. Although I had dried the powder well after synthesizing it, it still contained
significant amount of clumps. Adding this to reaction caused many lumps to remain even long time of strong overhead stirring, which was only very
slowly grinding them. So, I sieved the powder and crushed them batch by batch with simple pestle and mortar, and used hand cranked flour sifter to
grind the rest, and result was very fine and uniform powder which was administered to the reaction. I did all this in a transparent plastic trash bag
to eliminate dusting, which was very severe. Probably those small smoothie blenders could be used for this purpose as well for much faster
atomization.
Since I don't do these on daily basis, I took the long march to add them scoop by scoop over the hours instead of even thinking of any automated
solution, but if I were doing something as a routine, I would most certainly look into something like above.
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Texium
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They don't.
Not on a bench scale, anyway. In the labs I've worked in, liquids are added using syringes or addition funnels, and solids are dissolved in liquids
when possible. When it isn't possible, or easier not to, the solids just get added directly. If you have to add a solid to a very air sensitive
reaction, you can use one of those augur funnels, though in my experience, those are rarely used, and generally have a reputation for being more
trouble than they're worth, due to jamming up, leaving a lot of residue behind, and being hard to clean. A much more practical and frequently used
method is this: https://www.labdepotinc.com/p-63931-adapters-solid-addition-...
This whole ordeal sounds like a waste of time to me.
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zed
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Although, sometimes.... Pellet-stoves work. In fact, I wish I had one.
Here in the U.S., when grain prices are terrible, and Petrol prices are exorbitant....
Some folks, in the Midwest, have run their pellet stoves on kernels of Corn. Though I suppose, Wheat or Soybeans would be OK too. Midwestern Winters
can be brutally cold, and heating costs crushing.
Firewood is scarce, Petrol spendy, and Surplus grain... Will heat the house in a pinch.
So there. A solid materials, automated feed, continuous reaction system, I almost trust!
Oh, and maybe the Hourglass. The Hourglass is pretty reliable.
Though the Hourglass doesn't generally detonate, when there is a screw-up.
So, who here is a big enthusiast for the self-driving car?
Hmmm. Do I hear Crickets?
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Dr.Bob
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There is another option that was hot for a while, but has cooled off, which was to preweigh solids into dissolvable capsules or bags in specific
amounts, which could be just chucked into a flask or reactor. That is done for some larger scale reactions, where it is common to scale reactions to
the reagent that is hardest to handle, so pilot plants often run large scale reactions such that the key reagent is an even 500 g or 1 kg. Then that
reagent is chucked in the solvent and everythign is added to that in the correct proportions.
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LuckyWinner
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many experts have spoken now...
if you want automation...
I guess making your own powder screw funnel with a stepper motor
seems to be the best way for solids.
have a wide teflon valve attached to the bottom of this which will be closed after addition.
for liquids, pressurize the vessel which contains your liquid
and guide the liquid through a teflon tube into your reaction vessel.
have an electronic valve connected to the end of the tube which
can be closed after addition.
how would one weight out the liquid that is being added to the reaction vessel?
have an intermediary 'scale' vessel which is suspended on a hanging scale?
once x grams are reached pressure is equalized, valves opened...
[Edited on 15-3-2021 by LuckyWinner]
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Texium
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| Quote: Originally posted by LuckyWinner | use a hanging scale which holds an intermediary 'scale' flask.
the pump will stop once x grams are hanging down the scale.
whats the best way to transfer and weight powders?
there are POWDER ADDITION FUNNELS but how can you calculate the powder
that is being added?
any simple solutions for this? |
| Quote: Originally posted by LuckyWinner |
you could add a stepper motor to the glass powder addition funnel valve.
but
1. how to calculate the powder in grams that was added?
use 2 of these powder feeders, with 1 intermediary scale unit?
maybe make a custom stainless steel valve with teflon thread 24/40?
sounds complicated any simple solutions? |
| Quote: Originally posted by LuckyWinner | I guess making your own powder screw funnel with a stepper motor
seems to be the best way for solids.
have a wide teflon valve attached to the bottom of this which will be closed after addition.
for liquids, pressurize the vessel which contains your liquid
and guide the liquid through a teflon tube into your reaction vessel.
have an electronic valve connected to the end of the tube which
can be closed after addition.
have an intermediary 'scale' vessel which is suspended on a hanging scale?
once x grams are reached pressure is equalized, valves opened... |
Considering you keep asking the same
specific things over and over again, it seems like you probably won't stop until you're told what you want to hear. I'm gonna tell you what you don't
want to hear though. This "hanging scale" thing isn't a good idea. It wouldn't be accurate, and it would be very complicated to make. It's clear that
you haven't actually thought about the complexity of what you're proposing. So to answer your question "any simple solutions?" the answer is NO.
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Dr.Bob
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I have actually built a peptide type synthesizer, and to do it properly costs about $30,000 in parts, valves, tubing, etc. You can certainly build
something much cheaper that would do a single reagent, as the system I did would do solvent, 10 fixed reagents, and some variable ones, using a
complex system of parts that looked like an engineers nightmare. These types of systems, which are widely described every few years to replace
chemists, all impress idiots and executives with clicking valves, whirring motors, flashing lights and bells, but within a year of installation all
are discarded as useless. (I have seen and worked on a few from this up to multi million dollar automation systems, every one has been a disaster,
please note that I advocated against complex systems in every case and pushed hard for simple workstation level automation with people moving samples,
running the reactions, and transferring the items from system to system, as every system with robot arms, miles of tubing, or complex reactors failed
due to clogs, corrosion, leaks, spills, etc.
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