From: fernando@netnews.jhuapl.edu (Pineda Fernando J. RMI x8639 )
Subject: (M) water chemistry (repost)
Message-ID: <By6BuM.7Mt@netnews.jhuapl.edu>
Organization: JHU/Applied Physics Laboratory
Date: Mon, 23 Nov 1992 14:49:33 GMT
Lines: 26
Alright! This post should be uncorrupted. I've been very busy on work and personal things (papers for publication, teaching, getting married, etc.) so I had to put this on the back burner.
Nevertheless, thank you to everyone who e-mailed me helpful bits of information.
I'm now posting from a unix workstation rather than my MAC II. I sucessfully test-posted this to dc.test and it checked out. So hopefully from now on my posts should reach sci.aquaria intact.
To get a first pass quantitative understanding of Calcium and "Hardness" water chemistry I dusted off my old chemistry books, went to the library, did a few experiments, and made some phone calls. The result of this little exercise in recreational science is a set of notes that may be useful to others who are trying to understand what's going on.
These notes are still incomplete, but if there is sufficient interest I will continue to post my notes as I learn more. I welcome interactions with
SUMMARY
There are two main sections here. The first section summarizes the essential quantitative facts needed to understand some aspects of water chemistry. By "understand" I mean that one should be able to do calculations. The second section gives detailed information about test kits, i.e. what they actually measure and how they do it (chemistry!). This information was obtained by calling around to the manufacturers and discussing the chemistry of their kits. Also several people contributed via e-mail. I only ha
ve experience with the LaMotte calcium kit so there are some omissions in the descriptions of the other test kits. You may want to fill in the blanks and e-mail or post the missing parts. Here are some highlights, in no particular order:
LaMotte (and Hach) make test kits that measure total Calcium in solution and test kits that measure both Calcium and total hardness. With the latter kits you can estimate magnesium hardness too, but this is not too useful for aquarists. For people that have Ca hardness test kits I describe a delightful experiment that illustrates how the buffering effect of CaCO3 maintains the level of free Ca++ ions in solution. It demonstrates that that the time scale of the CaCO3 equilibrium reaction is ~5 seconds or le
ss.
The terms "Carbonate Hardness" and "Carbonate Alkalinity" are identical. They both refer to HCO3- and CO3-- concentrations. Measurements of these quantities are only indirectly related to the amount of calcium in the water through the
