I know nothing about them, but it looks to me as though either, that little protruding bit fits up into some kind of dimple on the bottom of a glass jar, or, there is supposed to be some kind of spacer between the vibrating thing and the jar, so you don't get glass on metal contact.
It is literally as you say , its a bit of metal screwed in , I assume this bit is fixed to the tank and then the transducer screwed on.
Anyway did some testing in the kitchen with the transducer suspended at the surface of the liquid.
Tried a few combinations.
1) Ground coffee and cold water.
2) Ground coffee and cold milk
3) SVO and water.
4) Water and granulated sugar.
Not much success at all really I think the transducer needs to be at the bottom of the tank , altohugh some interesting results with the coffee/water.
Seemed when I turned the transducer on the coffee granules all culmed together, firstly being dispersed evenly in the liquid after a stir then when on they coffee when it touched the side of the glass or other coffee grounds , then clumped.
I can see this may well speed up soap settling, as I would get all the soap to stick together.
I think the logic is that the water is a great conductor of sound and the coffee isn't so they tend to stick to the "quiet" surfaces.
Video
https://drive.google.com/file/d/0Bz9Uq7xWshaIdnIwdHFBejA0RmM/edit?usp=sharingSorry its uncompressed video , ~64Mb for the 15 seconds :O
