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Author: Subject: Cheap centrifuge
khourygeo77
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[*] posted on 8-11-2021 at 16:55
Cheap centrifuge


Hello,

I am looking to buy/make a cheap centrifuge in which I can put a recipient (maybe a flask of) and turn it to around 5000 rpm. I need to do the test on 100ml

So I was wondering if it is possible to buy cheap centrifuges or if it is possible to make your own centrifuge by buying cheap stuff like small cloth dryer and fixing the recipient in it?

I'm only looking to do a few experiments. I'm not sure if I can even rent a centrifuge for a day....

Any ideas?

Thanks for your time
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fredsci93
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[*] posted on 8-11-2021 at 20:20


Best to buy a cheap one used, most can handle 100ml (total solution spread across all the docks) and they go for reasonable prices (<80USD) on ebay or other local sources, however if you wanted to make one You could get decent speeds ~1000-2000RPM from a powerful corded drill with a sample holder of some kind attached. a cloth dryer/washing machine motor would be alright too at ~1000RPM, Just make sure to check what the speed of a given model is quoted as and that the sample holder is centred.
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Kobold vor NH4
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[*] posted on 9-11-2021 at 01:53


I brought mine for AU$60 from Aliexpress. It only goes to 4000rpm.

https://www.aliexpress.com/item/32891766851.html?spm=a2g0s.9...

It's alright, it's very plasticy, and I wouldn't rely too much on it, and the knob rattles around quite a bit at the 2nd, 3rd, 5th and 6th speed.
And it tends to drift along the tabletop quite a bit at the higher speeds. It does the job though.
I keep a good eye on it and never leave it untended while its running.
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Antiswat
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[*] posted on 9-11-2021 at 07:57


you might wanna put a counter balance, having a disbalanced spinning mechanism is how you create a vibrator

out of curiousity, what are you gonna use a centrifuge for? ive wanted to use one a couple times for extraction emulsions, im sure it would be really cool for general precipitation/washing procedures as im an avid user of decantation

edit:
i might add- if you intend to use the motor from a drill, the cord drills seems to just speed up infinitely, but you can take a battery driven drill, take apart and hook up to a power cable- then clamp the trigger on that and it can give you decently controlled power output

[Edited on 9-11-2021 by Antiswat]




~25 drops = 1mL @dH2O viscocity - STP
Truth is ever growing - but without context theres barely any such.

https://en.wikipedia.org/wiki/Solubility_table
http://www.trimen.pl/witek/calculators/stezenia.html
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khourygeo77
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[*] posted on 11-11-2021 at 07:58


I changed my mind. I think it will take lots of time and I'm not about the results as well. After doing some fast research, there are more effective ways of emulsion separations, and centrifuge doesn't perfectly do it as well. I'm going to follow NCBI research articles and make some conclusion. Hopefully, I'll find a more practical method. Thanks everyone for the help! I'll write the answers in case I see myself needing to make a centrifuge later on.

@antiswat. I intended to use it in order to break emulsions. It can be a substitute for distillations as well (but I am not sure). It can be useful for decantation but I normally can easily manage to do it by using a pierced metallic/plastic plate and covering it with linen cloth or tissue. (it's the type of plate you use in the kitchen in which you remove the excess of water out of the rice
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Tsjerk
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[*] posted on 11-11-2021 at 09:37


I used centrifuges to break emulsions when I worked in a lab, and it works like a charm, but 100 ml at 5000 rpm is a lot. You don't need 5000 though, 1000 is probably enough. Maybe it will take five minutes instead of one, but that is probably fine.

Centrifuges can even make filtering unnecessary, as you can often just decant the liquid which leaves an almost dry pellet. Too bad I don't own a centrifuge, and good ones are not cheap. But they are nice to have.
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Kobold vor NH4
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[*] posted on 11-11-2021 at 17:39


I use mine mainly to collect gelatinous metal ion precipitates, like Al(OH)3 and Cr(OH)3.
Like Tsjerk says, it compacts into a nice little pellet. And I also use it for squeezing some more liquid out of precipitates.

--Slighty off topic--
Hmmmmmm... I wonder what would happen if I crystallized something while it's in the centrifuge.

edit- found my answer
https://www.sciencedirect.com/science/article/pii/0022024868...
Might be useful for hard to crystallize compounds

[Edited on 12-11-2021 by Kobold vor NH4]
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khourygeo77
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[*] posted on 21-11-2021 at 05:28


Quote: Originally posted by Tsjerk  
I used centrifuges to break emulsions when I worked in a lab, and it works like a charm, but 100 ml at 5000 rpm is a lot. You don't need 5000 though, 1000 is probably enough. Maybe it will take five minutes instead of one, but that is probably fine.

Centrifuges can even make filtering unnecessary, as you can often just decant the liquid which leaves an almost dry pellet. Too bad I don't own a centrifuge, and good ones are not cheap. But they are nice to have.


Thanks for the info. I will keep this in mind. How do I know the approximate rpm that will break a volume of emulsion?

What is your experience about breaking emulsions? Like normally it took how much time? And how many rpm? What makes you think 1000rpm would be enough?

In this case, it is possible that a food processor, a mixer, blender or juicer might work?

[Edited on 21-11-2021 by khourygeo77]

[Edited on 21-11-2021 by khourygeo77]
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khourygeo77
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[*] posted on 21-11-2021 at 14:22


"Food processors operate at around 1,700 revolutions per minute, while blenders start at around 17,000 rpm and can go even higher than 30,000 rpm. More on the significance of that below."

So, with a high number of rpm, the emulsion is formed but with a moderate number of rpm (1000-5000) an emulsion is broken?
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macckone
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[*] posted on 21-11-2021 at 21:04


khourygeo77,

A centrifuge is going to break an emulsion by centrifugal force.
A food processor or blender is going to mix stuff together.

The first generates straight line pressure while the second generates sheer forces in addition.
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khourygeo77
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[*] posted on 23-11-2021 at 14:31


I don't exactly understand what you mean...
Is it possible to turn a Blender into a centrifuge with ease?
The razors in the Blender are what cause the shear force? If so if I remove them the blender will act as a centrifuge?
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MadHatter
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[*] posted on 24-11-2021 at 13:15
Blender


Removing the blades will do nothing for you. The vessel
containing the suspension needs to be spinning. I understand
what you're trying to do but a small medical centrifuge is
probably all you need or hand cranked model like I remember
from chemistry class(1975).




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Antiswat
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[*] posted on 18-12-2021 at 04:11


high power.... iirc angle grinders have a M14 bolt on it
so, construct some spinning blades of some sort that screws onto an angle grinder with M14 thread, it should tighten itself once it gets going, maybe adjust the power input with a volt limitor, may work but it might also just wanna not run at all then
angle grinders run at 12000rpm
powerful motor

otherwise a hand drill has a powerful motor, the ones that run entirely by cord will speed up indefinitely once it starts running, doesnt seem by my experience that you can slow them down, you need high speed anyways




~25 drops = 1mL @dH2O viscocity - STP
Truth is ever growing - but without context theres barely any such.

https://en.wikipedia.org/wiki/Solubility_table
http://www.trimen.pl/witek/calculators/stezenia.html
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aab18011
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[*] posted on 18-12-2021 at 07:24


I used a computer fan. It aint great for large scale, but if you are willing to tedious methods, it works. It really is only useful in a pinch and requires some sort of benchtoo power supply or a battery of some sort.

I basically mounted the fan face down onto a block (make sure the air can flow) and attached a little bracket onto the blade of the fan. I made a sort of holster for a test tube and then tested it with an emulsion. It works, but gets slowed down considerably if you fill it up enough. It technically can even do uneven loads, but the more even the load the better.




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