How red is "red"

[TimS]

I ordered the TF100 Thursday, and received it this morning. Talk about fast!! Saturday delivery, too!!!

Having had a chance to play with it, I have a question (that I also had with the HTH drop kit.) When testing for color changes (TA test goes from green to red) the solution goes from green to grey in the span of a couple of drops, then a couple more drops turns it a very definite pink. From this point, continuing to add titrant will continue to change the solution to a more vivid red, until it finally stops changing.

At what point is the solution considered "red?" When it's pink? When it's the next step redder than pink? When it stops changing minus one?

The same thing applies to the CH test, going from red to blue. When is it "blue?"

TIA

 

[anonapersona]

When there is no more change in color with another drop, then you were done.

So, green to grey, keep adding, grey to pink, keep going and be sure to swirl really well, pink to red, add and swirl really well, red to redder, add and swirl really well, then when no more redder then that last drop does not count since you were done with the prior drop.

But, I will note that I do not see red then redder, I just see it try to turn pink then go back to being grey as that drop is absorbed by swirling. Then, it goes strong pink and no more color change after that.

 

[polyvue]

Having had a chance to play with it, I have a question (that I also had with the HTH drop kit.) When testing for color changes (TA test goes from green to red) the solution goes from green to grey in the span of a couple of drops, then a couple more drops turns it a very definite pink. From this point, continuing to add titrant will continue to change the solution to a more vivid red, until it finally stops changing.

At what point is the solution considered "red?" When it's pink? When it's the next step redder than pink? When it stops changing minus one?

You brought up an interesting question regarding the Total Alkanlity test, which anonapersona answered one way and I will answer just slightly differently. I'm not sure which is more correct; however, my guess is that the instructions (and supporting science behind them) favor anonapersona's answer.

While the contents of the vial go through the usual interim colors (grey/green/whatever) I keep adding 1 drop at a time (and swirling) until there is a sudden and dramatic change. Usually that's to a pretty strong red or pink color. I stop there and record ppm. If in the first second or two after this change I note any reversion back to a dull, listless redish-gray etc, I add another drop, and that's where I stop.

The Calcium Hardness test is almost fodder for another thread. There are many aspects of this test (mostly the sometimes fuzzy end result to blue/violet/lavendar caused, I think, by mineral interference.)

 

[Butterfly]

Here's a link to water testing instructions from Pool School (in Further Reading):

water-testing-instructions-on-one-page-t11306.html

 

[TimS]

I just noticed that I had not responded to this thread after you all gave me the requested advice and guidance. For that, I apologize. I read your responses, and appreciated them all, but I failed to thank you for them. So....

Thank you all. You've been very helpful.

I finally got the pool balanced, closed, and covered. Now, we'll see what it looks like in the spring.

 

[fordsbyjay]

I am just gonna throw one more thing out there. I have noticed that if some parameters are way out of wack you might not see the colors indicated in the instructions. For example, if you take a sample while you have the chlorine up to shock level you might only see pink when adding the drops and never really see a red. I also noticed that when I accidentally added way too much salt my colors where not correct on all the tests until I got the salt level down to normal levels.

 

[PaulR]

That's true, various other parameters can affect the exact colors you see. But, regardless of what the actual colors are, you will see it (a) start to change, and then (b) stop changing. That's the important part.
--paulr

 

[moonscape]

The Calcium Hardness test is almost fodder for another thread. There are many aspects of this test (mostly the sometimes fuzzy end result to blue/violet/lavendar caused, I think, by mineral interference.)

I just did my first Calcium Hardness test and also wasn't sure at which point to stop. This thread had been helpful. It became pink at 140, but I'm wondering why it is even in range.

My water is so hard that it leaves scale on sink stopper, sides of the toilet bowl, everywhere. Most remarkable thing I've ever seen. Whole-house water softeners are the rule in my coastal town, but since I'm in a condo I don't have one.

Am really interested in how other mineral interference could affect this test, if that's what you meant.

 

[polyvue]

Am really interested in how other mineral interference could affect this test, if that's what you meant.

The test is designed to start with RED and end with BLUE -- not pink... but see below.

Though I haven't tested specifically for metals or other minerals in my pool, the level of Total Dissolved Solids (excluding salt) measures fairly high. When I conduct a Calcium Hardness (CH) test the solution isn't really very RED to begin with and the end point is nothing I'd want to call BLUE --- it's more of bluish-lavendar.

The makers of the Calcium Hardness test (Taylor Technologies) caution that

• Metal ions may cause interference; to prevent, add titrant containing EDTA to sample before buffer and indicator, then test as normal making sure to count drops of titrant added initially in total required to reach endpoint. If interference still occurs, dilute sample with DI water as necessary and retest.
  
  Source: Potential Interferences for Kit Number: K-2006

This procedural work-around may be helpful to some pool owners, but it seems to have no affect on the color of the end-point when testing my pool water. The way I distinguish the end point is to watch (carefully) for a sudden, dramatic change from pinkish-blue to bluish-lavendar. If I look away for a moment and miss this change, I have to start the test over with a new sample--it's that quick and subtle. Once I note the change, I add another drop to be sure it's done; the final drop is not counted.

 

[chem geek]

And don't forget waterbear's advice about thoroughly mixing for each drop -- waiting 30 seconds for stirring of each drop unless you are using a magnetic stirrer which makes the process go faster (highly recommend if CH is high; otherwise the test takes a long time to do). If you are using a separate tube as with the TF100 kit, then stirring even manually isn't too difficult.