carlton.hoyt
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Hi Jennifer. As you surmised, a paint mixer won’t really “homogenize” much. The disaggregation that you get from any overhead stirrer type of device is much less than you would get from an actual homogenizer. Here’s a decent rule of thumb:
- An overhead stirrer will break down immiscible particles (things that don’t naturally dissolve into the solvent) to around 100 micrometers (aka “microns” - in other words 0.1 mm) depending on the stirring conditions, what you’re stirring, etc.
- A rotor-stator homogenizer, depending on the probe used, can get particle sizes down to about 5 microns (0.005 mm)
- A high-pressure homogenizer, which are what are used in many industrial processes, can get the particle size down to around 100 nanometers (i.e. 0.1 microns, or 0.0001 mm) depending on the instrument, pressure, and what you’re homogenizing
- An ultrasonic homogenizer with sufficient processing can sometimes achieve particle sizes around 50 nm (0.05 microns).
YMMV based on the chemistry of your mixture, but ultimately a homogenizer will provide you with far greater disaggregation of your titanium particles than a mixer. A mixer is really a tool for blending miscible substances - things that will naturally dissolve in each other. A homogenizer is for the tough jobs when you really need to force substances to blend by reducing the particle sizes of the solutes.
The downside is capacity. Stirrers are much better equipped to handle large volumes, and ultrasonics in particular can be a PITA to scale up. They also don’t handle higher viscosity mixtures very well. You might be better off with a rotor stator, depending on what ultimate particle size you need. Rotor stators are easier to scale up, handle larger volumes at any given price point than an ultrasonic, and can process higher viscosity liquids (although not as high viscosity as overhead stirrers can handle).
Hope that helps!
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To provide some additional color for people who may stumble upon this old question (as I have), there is an immense practical difference between an immersion blender (or any blender) and a homogenizer.
Blenders use fast-moving blades to reduce particle size. They primarily impact particle size through cutting, and secondarily through shear forces.
Homogenizers pull the material into a very small gap between a central, very rapidly spinning rotor and a stationary outer shaft (the stator). Because of the massive difference in speed between those two parts, it creates huge amounts of shear forces.
While a very high-quality immersion blender may approach the RPMs of rotor-stator homogenizers, because the blade of the blender is essentially operating in open space, the shear force is relatively limited. It is the shear force which really gets small particle sizes. With a bladed instrument, you’re mostly relying on how small of a particle the blade can meaningfully impact before it simply gets pushed out of the way before impact due to fluid flow. The design of a rotor-stator actively sucks liquid up into the high-shear area in the probe.
A good immersion blender will provide a particle size of perhaps 100 µm (1/10th of a mm). A good homogenizer and probe can achieve particle sizes below 5 µm (1/200th of a mm). So the particle size will be quite different, and the smaller your particle size, the smoother and more stable your emulsion will be.
Of course, rotor-stators aren’t the only type of homogenizers. You can read about the use of other homogenization technologies in emlusification here: https://homogenizers.net/pages/ac-emulsification
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Just to help you (@pharma) troubleshoot should you ever try that again, that probably means that you set the vacuum too deep or your coolant wasn’t cold enough. The organic compounds giving the scent you wanted were likely so volatile that under vacuum they didn’t recondense when exposed to the coolant in the condenser - they were still gas at a temperature approximately that of your coolant at the pressure inside your rotovap.
… unless you were using a dry ice condenser, in which case something else was the problem and I’m way off.
It’s also going to be real tough to separate the one compound you want from all the others with rotary evaporation alone. An extract from flowers is going to be packed with all kinds of organics, a lot of which will probably have some scent. It may take a more complex distillation to effectively isolate the one(s) you want. Ultimately, distillation in a rotary evaporator is still a simple distillation - it’s just faster, more efficient, safer, and easier due to operating at lower temperature and with rotation.
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Neat device! I’d be curious what a particle size analysis on something it processed would tell us.