"y_p_w" > wrote in message
ink.net...

> Or one could go the typical Japanese manufacturer's route.
> They seem to prefer silicate-free but with good amounts of
> phosphate. Phosphates are supposed to be real problematic
> with hard water though.

One of the old ways to analyse for phosphate was to precipitate it as
magnesium pyrophosphate and weigh the dried residue.

For such a method to be useful, the salt formed needs to be practically
insoluble. That will give you an idea of why phosphates can be
problematic.

The big problem, as I see it, is protection of aluminum and its alloys.

Silicate is one of the few anions that will give aluminum protection
(and it isnt perfect either). It is too bad that its solubility quirks
cause so many problems.