From: fernando@aplcomm.jhuapl.edu (Fernando Pineda)
Subject: 2nd try: Water Chemistry (uncorrupted I hope)
Reply-To: fernando@aplcomm.jhuapl.edu (Fernando Pineda)
Organization: Johns Hopkins University/Applied Physics Labs
Date: Thu, 5 Nov 1992 16:15:04 GMT

The main body of the water chemistry post was missing on my last try! 
I think my posts were getting corrupted because 
my editor was using special characters. These were not getting 
stripped or converted when I output the file as an ordinary ascii 
text file. I've ported the text file around to various unix systems and 
looked at it with "more" and with "vi" it seems to be ok now. 
Also, I've switched to a less fancy editor on my MAC  and this should 
(HOPEFULLY)  solve the problem. If there seem to be missing pieces 
in this post or if there are funny characters, pleast let me know via 
e-mail. I'll fix it and send you an uncorrupted copy. I'd rather not
clutter the network with repeated posts. 

Sorry for the junk mail.

-- Fernando

______________________________repost___________________________________

My initial question about converting ppm CaCO3 to dKH resulted in
an explanation of the qualitative facts about hardness and alkalinity.
My request for the quantitative implications did not,however, meet 
with much success. So 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 go along.  


SUMMARY


There are two main sections here. The first section summarizes the

essential quantitative facts needed to understand and visualize some 

aspects of water chemistry. 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 have experience with the LaMotte 

calcium kit so I may have missed some information on the other kits.


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
less. 


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  reaction CaCO3 + CO2 + H2O <=> Ca++ + 2[ HCO3-].  


Thiel refers exclusively to dKH in his book (Advanced Reef Keeping). 

He gives 18.9 as the conversion factor to go from dKH to ppm CaCO3. 

Two points here. First, Thiel's carbonate hardness test kit actually 

measures total alkalinity but the difference between total alkalinity 

and carbonate hardness  is only about 3%, so for us aquarists, there's 

no point in making an issue of it.  Second, according to Thiel, you can 

convert from his dKH figures to total alkalinity in ppm CaCO3 by 

multiplying the dKH figure by 18.9. I work through a detailed example 

calculation below. Moe and Thiel don't completely agree on their ppm CaCO3

to dKH conversion factors. Moe gives the conversion factor as 17.9 or 

1/0.05 = 20, Thiel says 18.9.  The difference may be related to the ~3%

difference between total and alkalinity and carbonate alkalinity, but 

without further information I can't determine this. In any case, neither 
n factor as 17.9 or 
1/0.05 = 20, Thiel says 18.9.  The difference may be r
elated to the ~3%
diffe
r
ence between total and alkalinity and carbonate alkalinity, but 
without fur
ther information I can't determine this. In any case, neither 
t
Moe nor Thiel gives a satisfactory explanation of the "gotcha's" involved
 
in these conversions. 

Also, I'm still looking for more detailed data
 on the following test kits: 
Hach, Tetra, others?. If folks would provide me
 with customer service 
telephone numbers and as much information about a p
articular kit as they 
have, I can try to follow throug
h
 
and get more detailed information on 
their kits. I might add t
hat, I
 don't have infinite funds to spend on phone 
bills, so if anyo
ne else feels motivated to call and
 
get information on a 
particular test kit, that would help out considerably
Newsgroups: sci.aquaria,rec.aquaria,alt.aquaria