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Re: Aquatic Plants Digest V3 #6

Dave Gomberg wrote:

> >
> >Nine solutes comprise the vast majority of all minerals dissolved in most
> >water.  These are Ca++, Mg++, Na+, K+, HCO3-, Cl-, SO4--, NO3-- and SiO2. 
> Excuse the heck out of me Roger, but isn't SiO2 glass?  And isn't glass
> pretty generally INsoluble in water (and most other things)?   What give
> here?  Are you thinking of sulphur maybe (SO4?).  Enquiring minds want to
> know.

Sure Dave, your heck is all excused <g>.  SiO2 is glass, and quartz and
chalcedony and opal, and a few other things too.  I don't know about the
solubility of manmade glass, but quartz (the most common natural form) is
slightly soluble in water and if I remember right, water in the presence
of quartz at standard T and P saturates at about 21 mg/l. 

Concentrations can be higher than that because of elevated temperatures or
the weathering of some minerals.  My tap water carries about 60 mg/l
SiO2, so despite being rather soft it leaves some very stubborn mineral

I think most people will have 10-20 mg/l in their water supplies.

As a detail, the stuff is probably in solution as undissociated silicic 
acid - H4SiO4 - rather than as SiO2.  SiO2 in solution is essential for 
diatoms, which use it to make their "shells".

Roger Miller