False pH reading with Taylor kit: stating the obvious

[jwfrank]

maybe I can help others. I have been helped enormously by this forum

I occasionally have had very low, off the chart, pH readings when using Taylor kit. I would do a second test and the reading would be normal, where I expected it.

The reason, I discovered, was that in the cases where I did a FC test first, I was rinsing the test tube but not the black rubber lid. The liquid residue from the chlorine test on the lid was enough to violently throw off the pH reading which followed next

the obvious: clean both the plastic testing vial AND the lid

 

[Guest]

Which Taylor kit do you have?

If you have a K-2006 you do not use the black lid for the chlorine test since the vial should not be shaken but rather, swirled. The lid is used for the pH and acid/base demand tests but NONE of the other tests so there should be no cross contamination.
http://www.taylortechnologies.com/produ ... umber=5811

If you have a K-2005 or any other kit there is a separate lid for the chlorine and pH tests and they are either different sizes or different colors so they cannot get mixed up.

I guess this demonstrates the importance of reading the instructions.

 

[jwfrank]

Waterbear, point taken: Read and follow instructions

I have noted the "stir dont shake" instructions, and honestly , have ignored at my peril

Seriously though, what is the reason for SWIRL rather than shake to mix? It seems that in the FC test, the crystals dont always dissolve quickly, and hence in my impatience, I shake with cap on. It doesnt seem that I get different test results one way or the other

 

[JasonLion]

Chlorine can evaporate out of the sample if there is too much aeration, resulting in a lower than actual reading.

 

[Guest]

You can always invest in a magnetic stirrer. I use one and find it useful for all of the titration tests.
portable-magnetic-stirrer-from-apollo-pools-t1489.html