Re: Mystery Tank

In a message dated 12/21/96 3:08:04 PM, Paul Krombholz wrote:

>Now the mystery deepens even more because you have been adding this stuff
>from Aquarium Pharmaceuticals to raise the pH, and still you are titrating
>with your CO2 kit a whole lot of chemical (probably NaOH) to get to the
>phenolphthalein end point. I am assuming that your kits are using
>phenolphthalien as the indicator die.  If you get a pink color, that is
>what it is.  Is the ingredient in the Proper pH product, sodium
>bicarbonate, or is it something like Na2HPO4 (sodium monohydrogen
>phosphate)?  If it is the latter, I can see that it could act as a buffer
>to  hold the pH below 8.  (The phenolphthalein end point is about 8.1) Try
>this experiment.  Take a quart of tap water aerate and test for CO2 as
>before, and then add some of the Proper pH product and test again.  If it
>takes a lot more to reach the phenolphthalein end point, then we know where
>the problem is coming from.  If you do get these expected results, then it
>looks as though you can't use your CO2 kits if you also use the Proper pH
>Paul Krombholz                  Tougaloo College, Tougaloo, MS  39174
>In chilly Jackson, Mississippi.  

I got the same result after adding the "Proper pH". The I received the
responce from Jim Layton @ AP.

I started playing around with iron and the CO2 method you are using.  
Using chelated iron, the CO2 tests is only very slightly "fooled" by 
iron.  At 1.7 ppm chelated iron, the C02 test gave a 3.0 ppm false 
positive test, over what was actually in the water.  Now I eat my 
words.  Proper pH, and other strong buffers, will keep the end-point 
color from forming.  The phenolphthalein indicator starts to turn 
pink at about pH 8.3.  The sodium hydroxide is titrated, drop by drop,
 until the pH is increased, giving the pink end-point.  Proper pH and 
other true buffers, will inhibit the pH increase in the test tube, 
causing you to keep adding the hydroxide.  This causes you to add 
lots of drops, until the buffer is overcome and the pink color forms.

Well-that seems to explain all or some of your high CO2 situation.  
Cool.  How much proper pH did you add? 1X dose?  I don't recommend 
the product for planted aquariums, due to the phosphate buffer. I'm 
playing around with some other "things" that may screw-up the CO2 
test kits.  I'll post them in the next Layton Lab report, which will 
have mostly plant-related topics.  I'm very glad you brought this to 
our attention!  Pass on the information.

Jim Layton

Thank you all for your interest and I am still in the process of doing water
changes to get rid of those buffers.

Best to you..............Ric
Ric Cooney, N3BRB
Mailto:RicCooney at aol_com
"Maryland is for Crabbs....................I'm Trying to do my Share"