Magnetic stirrer questions

[ॐ]

Hi fellow Nexians,

I bought myself a magnetic stirrer / hotplate recently, along with a 2L Erlenmeyer flask which I was planning on using as an extraction vessel, and a number of different size stir bars.
I've tested it out quickly, but noticed that it was not evident to stir 2 liters of fluid, even with the largest stir bar (9x70mm). I can only stir this much fluid on the lowest speeds, producing a very small vortex of barely 1.5-2cm, otherwise the stir bar just goes flying.
Using a 0.5L Erlenmeyer I could create a large vortex with ease. I also have a 1L glass beaker which I haven't yet tried but presumably would also draw a fairly decent vortex.

I have a few questions:

1. How much of a vortex do you really need to properly mix the naphtha and base soup?
I presume you would want one that sucks in 90% of the naptha, leaving just a small film on the surface?

2. Can you use more powerful magnetic stir bars to draw a larger vortex in a higher volume of liquid?
The ones I am using right now are off-brand teflon coated stir bars. I have read that neodymium stir bars are a lot more powerful than most other:

Many stir bars are made with ceramic or Alnico magnets. Ceramic magnets are inexpensive and common, but not nearly as strong as a neodymium magnet. They have only about 8-10% of the pull force.

Alnico magnets are made from aluminum, nickel and cobalt. They are stronger than ceramic magnets, about 25% of the strength of a neodymium magnet of the same size. They have been commonly used for stir bars, especially for high temperature use. The downside is that Alnico magnets have very low coercivity, meaning they are easiest to demagnetize. If exposed to a strong magnetic field, they can become weaker. They are often sold in pairs to avoid this, though they can lose strength through mishandling.

Neodymium magnets are stronger than ceramic and Alnico magnets, and have the highest coercivity of all permanent magnet types. If you keep the temperatures of these N42H grade Stir Bar Magnets below 248°F (120°C), they should retain their magnetization practically indefinitely

Seems like this would be my solution?

 

[Psilosopher?]

Hi fellow Nexians,

I bought myself a magnetic stirrer / hotplate recently, along with a 2L Erlenmeyer flask which I was planning on using as an extraction vessel, and a number of different size stir bars.
I've tested it out quickly, but noticed that it was not evident to stir 2 liters of fluid, even with the largest stir bar (9x70mm). I can only stir this much fluid on the lowest speeds, producing a very small vortex of barely 1.5-2cm, otherwise the stir bar just goes flying.
Using a 0.5L Erlenmeyer I could create a large vortex with ease. I also have a 1L glass beaker which I haven't yet tried but presumably would also draw a fairly decent vortex.

I have a few questions:

1. How much of a vortex do you really need to properly mix the naphtha and base soup?
I presume you would want one that sucks in 90% of the naptha, leaving just a small film on the surface?

2. Can you use more powerful magnetic stir bars to draw a larger vortex in a higher volume of liquid?
The ones I am using right now are off-brand teflon coated stir bars. I have read that neodymium stir bars are a lot more powerful than most other:

Many stir bars are made with ceramic or Alnico magnets. Ceramic magnets are inexpensive and common, but not nearly as strong as a neodymium magnet. They have only about 8-10% of the pull force.

Alnico magnets are made from aluminum, nickel and cobalt. They are stronger than ceramic magnets, about 25% of the strength of a neodymium magnet of the same size. They have been commonly used for stir bars, especially for high temperature use. The downside is that Alnico magnets have very low coercivity, meaning they are easiest to demagnetize. If exposed to a strong magnetic field, they can become weaker. They are often sold in pairs to avoid this, though they can lose strength through mishandling.

Neodymium magnets are stronger than ceramic and Alnico magnets, and have the highest coercivity of all permanent magnet types. If you keep the temperatures of these N42H grade Stir Bar Magnets below 248°F (120°C), they should retain their magnetization practically indefinitely

Seems like this would be my solution?

You'd still need to shake the solution to get it thoroughly mixed. The hotplate stirrer just causes the liquid to be in constant motion, so that all of the base soup is coming into contact with the solvent layer. As long as you can see the solution moving, you're fine. DMT doesn't like base, so it'll dissolve in the solvent rather easily. I'd personally be more than satisfied with something that stirs. Doesn't have to be powerful.

I'm on the hunt for a hotplate stirrer myself, but mainly for the acid cook. This is to keep the bark constantly moving instead of clumping up.

 

[Spaced Out 2]

There are other shapes you could try, (cross, wheel, triangle [shaped like prism], but I agree that I don't think a little home hot plate/stirrer is going to create enough turbulence to suck the nps down into the basic soup and circulate it around, boy it would be nice if it did.

My corning pc-351 does the same thing with my bar as well, if I turn to highest setting it's fine for a few seconds and then goes crazy, set it at three quarters the way and it stabilizes.
But for the step you're talking about I just do it the old fashioned way, shake the hell out of it a bunch of times.

 

[Trickster]

Why so much basic solution? I always reduce the volume of acidic solution to ~300 ml. After basification I get ~350ml of liquid. This allows me to use a 500 ml separatory funnel to separate NP solvent. So there is no problem with the stirrer.

I do not like shaking the solution because it creates emulsion (esp. when the solution is warm) that makes separation of layers difficult.

 

[ॐ]

Thanks for the advice, everyone.

I'm on the hunt for a hotplate stirrer myself, but mainly for the acid cook. This is to keep the bark constantly moving instead of clumping up.

I failed to mention this in my initial post, I got my stirrer/hotplate specifically to make the acid soak less of a hassle as well, it seems especially useful for this step. I was just wondering what the most optimal technique was when using a stirrer to aid in getting most of the dmt to migrate to the naphtha. I'm sure just shaking/rolling works fine, but I'd like to get more control over the process by using the stirrer if possible.

There are other shapes you could try, (cross, wheel, triangle [shaped like prism], but I agree that I don't think a little home hot plate/stirrer is going to create enough turbulence to suck the nps down into the basic soup and circulate it around, boy it would be nice if it did.

Thanks for the suggestion, I will look into the different shapes, this could be interesting
It seems the right type of stir bar magnet can make all the difference here :shock:
[YOUTUBE]

Why so much basic solution? I always reduce the volume of acidic solution to ~300 ml. After basification I get ~350ml of liquid. This allows me to use a 500 ml separatory funnel to separate NP solvent. So there is no problem with the stirrer.

I do not like shaking the solution because it creates emulsion (esp. when the solution is warm) that makes separation of layers difficult.

I was planning on following Cyb's Max Ion to the T, which uses a total volume of 2L.
Reducing the volume before basifying sounds like a great idea though, that will definitely allow me to get a bigger vortex going with the stirrer. I might give it a quick, light manual shake while the naphtha is still hot, and then give it a long magnetic stir afterwards before pulling. How long would you stir it for to get most of the dmt into the nps? 30 minutes would do per pull, or would longer be better?

 

[Spaced Out 2]

The few I mentioned, as for your video, yeah that's a little stronger than my stirrer. It's got my gears turning though :thumb_up:

 

[downwardsfromzero]

If all you're doing is stirring base soup with NPS, you might as well use an overhead mechanical stirrer which won't stall anywhere near as easily as a magnet can. It can also be rigged pretty easily ghetto-style. (I won't deny the usefulness of a magnetic stirrer, of course. Especially with a hotplate.)

How long would you stir it for to get most of the dmt into the nps? 30 minutes would do per pull, or would longer be better?

Lots of small, short extractions are better than one long, large one.

Will you be syphoning the NPS off?

 

[ॐ]

Lots of small, short extractions are better than one long, large one.

Will you be syphoning the NPS off?

I will be doing just that. I have quite a bit of bark that's been lying around for a while now, but I will be doing multiple small extractions (Cyb's Max Ion which I plan on following uses just 100-150g of bark, but the total liquid volume is around 2L). I think I will be reducing the acididc solution prior to basifying as has been suggested, seems like that would be the best way to go.

I have a seperatory funnel, glass turkey baster and pipette to seperate the NPS, will probably decide on the spot which one will prove the most useful.

 

[ॐ]

I'm on the hunt for a hotplate stirrer myself, but mainly for the acid cook. This is to keep the bark constantly moving instead of clumping up.

Just thought I'd post a quick update. I have the hotplate stirrer running right now, stirring ~715ml of fairly thick acidic MHRB solution. It works wonderfully to get the bark in constant motion while lightly heating it up. Initially I had some problems getting it to stir, but this was mostly because the stir bar I had put in was too large. I switched to a smaller one and am getting a nice small vortex going. I'd definitely recommend picking one up, this really makes the long acid cook efficient and hassle-free :thumb_up:

 

[anne halonium]

my mag stirrer has it uses.
but remember,
"air powered mixing tools are your bestest friends"

^all the powa, all the fun, no sparks anywhere near!

 

[downwardsfromzero]

Of course, air-powered mag stirrer would fairly easily achievable!

 

[anne halonium]

easily achievable!

Google

^no magnets needed...........work without limits.
fact is , magnets bog down in many real world applications.

from a website..........

Compressed air is a great source with which to power mixing equipment. It is intrinsically safe to operate in high solvent environments as well as allows you to inexpensively control the rotation of the shaft. Some downsides of air are the high volume requirements for air flow necessitating large compressors/reservoirs for sustained operation and the fluctuation of speed based on the impeller resistance in the fluid.*


* annies note.......your gonna want a good compressor naturally.
"studio 3" foam @ 4 inches of soundproofing solves the noise issue for urbanites,
and silicone pads kill the vibration!:thumb_up:

^annie, always the thoughtful neighbor.

 

[Randomness]

Just a word of warning

I have a lab grade hot plate stirrer that I have used for extractions. It works wonders for the acid phase to help break everything down (after dry blending). It also works wonders for when you add a base to the mix you can see the colour change in the solution and the alkaloids precipitation (if you have enough). What you have to be careful of and should avoid at all costs is using to mix the solvent in. Stirring the solution works perfectly if the solvent is sitting on top of the mix. All parts of the solution are brought into contact with the solvent and the alkaloids will migrate. If you mix the solvent and basic solution together (blend them together) what you will have is an emulsion that will be near impossible to separate :-( I found out the hard way. Stir but not so hard to create a vortex that will consume your solvent.

You have been warned

Just to add with MHRB you should get everything out in two short (less than 3 mins) pulls of solvent (80% or so in first pull). Temperatures also make a difference 60c will give you something resembling what people called "jungle spice". Room temp will give clean xtals but might need a 3rd pull. Would recommend pulling immediately after addition of base or even adding solvent mid way through base as it will catch the alkaloids as they precipitate.

My procedure would be

Mix 100g blended MHRB with enough vinegar to make a "paste" resembling Thai red curry paste, put in heatproof container with cling film on top and microwave. When cling film starts expanding due to steam buildup stop and remove, cling film will now collapse and vacuum seal. Then leave for 12+ hours.

After leaving to sit I then mix with enough water to make a solution that will stir I mix with magnetic stirrer with no heat for 8 or so hours. After doing this step solution will quickly settle upon ceasing stirring.

Once stirred sufficiently I get my base and solvent together set temp to 60c, stir on a medium speed and slowly add base. The base will heat the solution and through careful observation it is possible to tell when additional base has no effect. I then immediately (but slowly) add 30 to 50ml of solvent and being careful not to "mix" or emulsify stir for two mins. I then carefully pull solvent with warmed glass syringe and put into cool glass dish where little crystals come crashing out. I then take a second pull for a similar time. Usually the second pull contains more plant fats and is more reminiscent of "jungle spice" you can keep these separate for different grades or combine.

Then I freeze precipitate.

This method is what works best for me

 

[tseuq]

I thought of getting a lab magnetic stirrer with hotplate, I would go for a used one, but reading through this thread rises ambiguities. So, it does a good job when it comes to the acidification and basification phase of the root bark but should not be used, or just with a lot of care, in the pulling phase? Like that?

Stirring the solution works perfectly if the solvent is sitting on top of the mix. All parts of the solution are brought into contact with the solvent and the alkaloids will migrate. If you mix the solvent and basic solution together (blend them together) what you will have is an emulsion that will be near impossible to separate :-( I found out the hard way. Stir but not so hard to create a vortex that will consume your solvent.

I find this a little bit confusing. So, in the pulling phase, when I put the naphtha into the basified mix and it firstly sits on top it is ok to slowly stir while creating a vortex but a strong blending should be avoided?

hum..


tseuq

 

[1ce]

easily achievable!

Google

^no magnets needed...........work without limits.
fact is , magnets bog down in many real world applications.

from a website..........

Compressed air is a great source with which to power mixing equipment. It is intrinsically safe to operate in high solvent environments as well as allows you to inexpensively control the rotation of the shaft. Some downsides of air are the high volume requirements for air flow necessitating large compressors/reservoirs for sustained operation and the fluctuation of speed based on the impeller resistance in the fluid.*


* annies note.......your gonna want a good compressor naturally.
"studio 3" foam @ 4 inches of soundproofing solves the noise issue for urbanites,
and silicone pads kill the vibration!:thumb_up:

^annie, always the thoughtful neighbor.

most l stirrers won't spark, and pumping gasses into air sensitive solutions seems counter intuitive.

for high volume stirring on the mag plate I just use a crossbar sryle stirbar. I swirl the flask so that the fluid starts to swirl in the same direction as the stirbar. Then I turn it on, starting slow amd gradually increasing strength.

works well for my uses.

 

[Ulim]

Maybe just a common lab shaker/rocking mixer will work?

Those are usually better off with high amounts of liquids. Also they are not as harsh so you dont make an emulsion. They are also pretty easy to diy.
I even saw someone use one while having a hotplate on top of it.

Or you could use something similar to a rotovap. Would also be easy to diy. Just a belt that makes your bottle spin.
I build a ball mill once. Just put in your soup into a bottle and let it roll around for a bit.
It would be better if the bottle would spin itself.
I think im going to build something like that just to try it.

 

[blue.magic]

The triangular stirrer is good at making vortices.

I however mix the naphtha by capping and inversion + swirling. Stirring can be good to promote emulsion breaking and resolution.