One of the projects I am working on for a client involves dispensing a precise amount of powder to be mixed with a solvent. For the moment, I have settled on a vibratory dispenser and spent some time today testing an inexpensive unit I purchased on Amazon. It performed as expected but I learned that vibration frequency was possibly even more important than intensity in determining flow rate. I did my initial experiments with salt (because it was handy) and need to repeat with the actual powders of interest.