> > I've just cut open a filter, for curiosity's sake, and I'm
> > quite surprised - there's not much carbon in there, but a lot of
> > what I take to be polymer beads - I guess about 25:75.
>
> These sound a bit like ion-exchange resins (can't remember the proper
> name), we used them in A-level chemistry. I think the school I was at,
> also used them for producing "deionised" water.
> There are two varieties. One will swap cations for H+, the other will
> swap anions for OH-. No more was explained. It was assumed that exchange
> was complete (you usually had to send some "cleaning" water through,
> before use - to clean the dregs from the last person!). We used them for
> cation counting. Once the cations were exchanged for H+, titration with
> an indicator and an alkali would give you the original cation count.
> Using both resins, should remove both anions & cations, with the H & OH
> combining to produce H2O.
> The beads we used were orange. I don't know where you get them from. I
> doubt they'll remove many organics.
> If I remember correctly, they could be "recharged" by running strong acid
> or alkali (respectively) through the beads.
That sounds quite right.
25 years ago I was in a laboratory that used stuff like that.
One cylinder H+ swappers and the other one OH- swappers. Was regenerated by
rinsing with HCl and NaOH. Colours dark brown and light brown.
I still have one litre of both types, but I've never tried to use it because
it looked so difficult to balance the system to get neutral water out of it.
They also had an electronic measurement equipment to gard the output
quality, which of coarse I couldn't do that easily at home.
Regards, Wim.
----- wim@djo.wtm.tudelft.nl -----
(wim@morgana.nl)