Testing Calcium

Jump to latest Follow Reply
S

Steve456

0
LifeTime Supporter
Jun 3, 2008
132
Texas
In previous posts readers have been advised in testing calcium that you need to keep swirling the vial for 20 to 30 seconds to mix thoroughly between drops. If your calcium level is near 300 ppm then the test would require 10 to 15 minutes. Are there any valid means to speed up the test and still achieve accurate results?

For example, can you quickly mix the first 20 drops since you know your pool calcium level has consistently tested above 200 and pool calcium levels do not change quickly?

If you do not mix thoroughly does the calcium test give results that are too low, too high, or just plain unpredictable?
 
Steve, you can do the 'multiple drops at a time' method without problems :) If I know the CH is going to be 300+, I'll do 20 drops, swirl for 30 sec then 5 and swirl, 5 and swirl,, then do a drop or 2 at a time...If you get the endpoint after adding multiple drops, you may have overshot the mark :x You can either repeat the test and not add as many drops at a time when you get close or, if you are doing 2 at a time, just accept that you could be off by 20ppm 8)
 
waste said:
Steve, you can do the 'multiple drops at a time' method without problems :) If I know the CH is going to be 300+, I'll do 20 drops, swirl for 30 sec then 5 and swirl, 5 and swirl,, then do a drop or 2 at a time...If you get the endpoint after adding multiple drops, you may have overshot the mark :x You can either repeat the test and not add as many drops at a time when you get close or, if you are doing 2 at a time, just accept that you could be off by 20ppm 8)
Click to expand...
Ted, actually it can create some problems. If there are any metals present adding the EDTA titrant too quickly is a sure recipe for a 'floating endpoint' .
a better way if you know you have a very high CH would be to use a 10 ml sample, 10 drops of calcium buffer, 3 drops of indicator, and then when you titrate each drop of titrant is equivalent ot 25 ppm CH It's a lower resolution test but if your CH above 300-350 ppm it's really all the precision you need.

Also, it is possible to get results that are too high if you do not mix well after each drop. Often, when you take the time to do the test right you find that your CH was not anywhere near as high as you thought.
The only preactical way I have found to speed up the test without getting inaccurate results is with a magnetic stirrer.
 
You must log in or register to reply here.
Thread Status
Hello , This thread has been inactive for over 60 days. New postings here are unlikely to be seen or responded to by other members. For better visibility, consider Starting A New Thread.
Top Bottom
Back
Jump to latest Follow Reply