Volumetric Flask Shaking


Not having a background in chemistry, I am stumbling around trying to build my information of shaking flasks, specifically volumetric flasks.

 To explain further, I am working on an idea where I am creating a digital twin of some equipment where we can analyse the best way to shake/mix fluids (maybe even sometimes a solid dose) in a volumetric flask. 180 degree Inversion always seems to be the normal practice but I have also seem people rotationally swirling in an upright position.

Any information or a point in the right direction would be greatly appreciated.

With best regards


  • It will depend on the relative densities of the compounds  you are mixing, and how viscous they are. It will also depend on how non-uniform you are happy for things to be at the end of the mixing process. some activities like dissolving a sparingly soluble salt in water are surprisingly lumpy and need a  lot of work to mix. Inversion is useful with widely varying density as it counters vertical stratification (heavy stuff at the bottom) as no amount of swirling hopefully  really works for that...

    In industrial settings and for things like processing of medical samples, where the variation of hand waving is not acceptable, magnetic stirrers or overhead stirrers are used on a timer in the cases when flasks are used at all. Overhead stirring with a propeller style head can be used to pump material vertically and can be as good as inversion. Only works with chemicals that do not attack the stirrer of course.

    Full scale manufacturing chemistry usually involves optimized mixing vessels, pumps etc. (think more like an oil refinery or a bakery.)

    Note that some things are best mixed hot for speed, or on the contrary for some thermally reactive things like explosives, better in the cold, or for others like photosensitive chemicals, in the dark. To be general, your 'digital twin' will need a lot of inputs.


  • Hello Mike
    Thank you - that is great information.
    To explain further, I have worked on a client based project where we were given the requirements for shaking and I was looking to develop a generic design of equipment that could be tailored to suit individual requirements.
    One other thing to ask, I assume a volumetric flask was used, as the vessel which is shaking ,as the user is able to be precise with volume.


  • yes - a 'volumetric flask' is just one with marks in the glass for known volumes, usually in milli litres l, but in very old kit also seen in pre-metric units like floz. It is as precise as the eye of the user and the levelness of the surface on which it stands relative to local gravity.

    Again in mass processes other non-human methods are favoured such as measuring the weight, or adding liquids via a dispensing pump. Humans wobbly hands and glass stoppered bottles are OK in the school chem lab and maybe on the R and D benches, but not in repeatable commercial processes.


  • Yes, I understand the human element not being as precise as a repeatable commercial process. It does make me question some existing equipment I have seen where the human element is definitely in use as part of a commercial process (This was at a large well known international pharmaceutical). Maybe in this instance it is at an earlier stage of the overall process.
    One more question please - either if it is a school chem lab or even a commercial process - how do you determine whether the mix/shake is successful/correct. School lab - by eye?, Commercial process - from R&D previously carried out?


  • pretty much - the skilled hand will know which substances dissolve quickly or mix easily - obvious when dissolving powders as you can see the residue, but harder with mixing two clear liquids - which seems to be about 90% of lab chemistry .. There are tables of solubility and so on, but like skilled cooks, no-one looks at that after the first few.

    There are many processes where the exact mixing does not have to be that perfect, and that probably saves the day more than folk realise.


  • Thank you Mike.

    Do you work in this field?

    I am trying to gauge whether this is idea/equipment that is of use and then in turn marketable. Developing a model, using a twin, that can optimise mixing that can then be turned into actual.

  • No, this is not my area of expertise. That could be probably best described as electronics with specialty in RF/ microwave, with some laser driving and pulse power. However I have spent a long time in a research lab environment before my current job, and I do still occasionally  get to work in and see other folks facilities from time to time. I do work along side a number of folk with various  skills and some of it rubs off.


  • Well it has been a help to me Mike, thank you. I meet with the guys at Siemens for initial discussions on digital twins which I will then float to some contacts I have in pharmaceutical to see if it has legs.