Reading the OTO PH Test

[Vandergraff]

I have a TF-100 and am very happy with most of the tests.

However I find using the OTO PH test to be somewhat of a guess. The block seems to go from orange thru red to purple. However my test samples always seem redder than the block. Most the time I think I am somewhere in the range from 7.5 - 8.0 - but exactly where I am in this range is really a guess.

Any hints on making a more accurate reading?

My fill water is well water with high PH - so I really would like a way of getting a better measurement.

I have read some of the posts on digital meters here and the consensus seems to be the requirement to regularly calibrate makes them a bit of a pain.

My other levels currently are FC 5, CC 0, TA 100, CH 240, CYA ~45 (I find this one a bit of a guess as well)

 

[Isaac-1]

It help to hold it up a uniform white background, also remember you are trying to match the hue of the color not the intensity, I find it also often helps to add an additional drop of reagent to darken the color.

Ike

 

[JasonLion]

Really bright back light, for example holding it up to a white wall in direct sun, or to the sky, helps a great deal, as does practicing. If you have the K-2006 with acid and base demand, playing around with the acid and base demand reagents to move the color up and down often helps you learn what the different colors look like.

 

[Flotsam]

Really bright back light, for example holding it up to a white wall in direct sun, or to the sky, helps a great deal, as does practicing. If you have the K-2006 with acid and base demand, playing around with the acid and base demand reagents to move the color up and down often helps you learn what the different colors look like.

Jason - that's a GREAT tip !! I ran out of the Taylor R-0871 reagent (K-2006 kit) and had to revert to the old AquaChem test kit (so simple - so inaccurate !) I'll remember this tip when I run out of reagent (again ).

Please consider adding it to the "Tips and Tricks" post ... where ever it is (I'm gonna cut and paste to my file ... ). Thanks !!

Mike

 

[Vandergraff]

Really bright back light, for example holding it up to a white wall in direct sun, or to the sky, helps a great deal, as does practicing. If you have the K-2006 with acid and base demand, playing around with the acid and base demand reagents to move the color up and down often helps you learn what the different colors look like.

I'll try the bright back light to see if it helps.

I have the TF-100 - can I just get the reagents or do I need to to get a K-2006 to 'practice'?

Thanks

 

[JasonLion]

The acid and base demand reagents are available separately. For the TF100 you want R-0015 and R-0016.

 

[Vandergraff]

Previously I had been using the Taylor brand R-0014 PH indicator solution - and as I say above the reading always looks redder than the block. Today the Taylor solution ran out and I used an Ace Brand PH indicator - amazingly the color looks spot on for PH 7.5. Both say they are 'Phenol Red'. So:-

1. I am surprised there would be any difference in color between the 2 solutions.

2. Hopefully the Ace solution is accurate - if it is it seems easier to read.

 

[JesseWV]

Previously I had been using the Taylor brand R-0014 PH indicator solution - and as I say above the reading always looks redder than the block. Today the Taylor solution ran out and I used an Ace Brand PH indicator - amazingly the color looks spot on for PH 7.5. Both say they are 'Phenol Red'. So:-

1. I am surprised there would be any difference in color between the 2 solutions.

2. Hopefully the Ace solution is accurate - if it is it seems easier to read.

Your old solution was probably somehow more concentrated Phenol Red, perhaps left open in the sun? You probably could have used 1 or 2 less drops with it to get a darkness matching the color squares.

The OTO is actually Orthotolidine which is for the chlorine test.

 

[Vandergraff]

Interesting - no the Taylor R-0014 hadn't been left in the sun - it lived in the pump house (no not the 'pool pump house' the 'well pump house').

It does sound like the Taylor R-0014 solution may be more concentrated than the Ace solution - I don't remember what solution originally came with the TF-100. The Taylor R-0014 was bought at Leslie's when the original solution ran out.