Questions about the free and combined chlorine test with the Taylor K-2006 kit

[ducru]

I just purchased the Taylor K-2006 kit, and am now running a first set of tests.  Whereas most of the tests are pretty basic and simple to carry out, the free and combined chlorine test, is stumping me.  Because it is less black and white, and requires a little more interpretation, it is giving me varying results.  The instructions are to fill the tube with required amount of water and add 2 dippers of R-0870.  First of all, who invented the word ''dipper'' and what exactly is it ?   Am I using the spoon as a measuring spoon (2 level spoonfulls) which I am pouring into the tube, or am I simply dipping it into the pot and adding whatever is left on the stick, to the tube ?  Then  the instructions state ''if free chlorine is present, the water will turn pink.  If the pink disappears, add R-0870 until it turns pink''.  What about if it never turned pink ?  Do I add the R-0870 in this case also ?  Once it does turn pink, it asks to add R-0871, drop by drop, until the pink disappears.  At one point, the pink does disappear, but if you wait 30 seconds or so, the pink color starts coming back again.  At this point, should I be adding more drops of the R-0871, or should I assume that once it becomes colorless, albeit for a few seconds only, I have achieved my goal ? How are others carrying out this test and interpreting the results ?  These are not life-altering questions, but they are causing my results to vary quite a bit. Thanks for your feedback.

[chem geek]

Use "dipper" means a level spoonful using the plastic spoon provided in the kit.

If there is no initial pink from when you add the DPD R-0870 powder, then there is no Free Chlorine (FC) in the water, BUT if the FC is very high then it can bleach out the DPD so result in a "flash" of pink that quickly disappears.  That's why they say to try adding more powder.  If you don't see any flash of pink or any pink after 4 level spoonfuls then you have 0 ppm FC.

You should not wait 30 seconds or so for the pink to return because that can be "bleed through" of CC into the FC part of the test.  You stop when it goes from pink to clear and use that number of drops for your calculation (for a 25 ml sample, it's 0.2 ppm per drop while for a 10 ml sample it's 0.5 ppm per drop).  You then add the potassium iodide R-0003 reagent and if there is CC then it will turn pink again and you add more R-0871 drops until that again turns clear and the count of those additional drops are used to calculate CC.

Perhaps this link to Taylor videos will be helpful.  Click on "Pool / Spa" on the left and then click on the "To Test (Free and Combined) Chlorine using FAS-DPD  [updated 3/5/10]" link under "K-2006 Complete™ Kit with FAS-DPD:" to see a demo video.

[ducru]

Thank you chem geek; that's exactly what I needed !