On Mon, 18 Jun 2018 15:39:25 +0100, Harry Bloomfield wrote:

That seems a bit big and rather expensive at $699.

That was just the first one I found. There are smaller and cheaper agate
ones available.


How about something smaller, more suitable and a lot cheaper -

https://www.ebay.co.uk/itm/282968704731 £1.94 each


Here's why not: https://en.wikipedia.org/wiki/Adsorption

Remember he's dealing with very tiny quantities.



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