Need help with Taylor Calcium test kit

[JimK]

(Sorry for the long post. If you want to skip the background info and get to the heart of my question, skip to the bolded section.)

Years ago I purchased a Taylor calcium test kit. According to the instructions at that time, I was to add drops until the sample turned from purple to blue. I was unable to tell when that change occurred, so I gave up on it an just relied on pool store testing for calcium.

Fast forward to now. Recently Ben asked me what my calcium level was and I gave him the figure from my last pool store test for "Total Hardness". Looking at my records for the past many seasons, TH seems to always seems to be in the 200-260 range (most often 240ish to 250ish). BTW, the nearby pool store uses a computer (Alex?) to test; sometimes it gives wacky results so I don't really trust it. The closest store that uses the Taylor kits is over a hour away.

Out of curiosity, I looked on the Taylor site to see if there was another test kit available. In the current instructions, it indicated the sample will change from red to blue. I figured this must be a change from the old kit and thought I could probably see the change from red to blue.

Today I bought the appropriate reagents and followed the instructions carefully. The sample initially did not turn red as indicated in the instructions; best I can tell it turned kind of very pale pink/purple. Adding the reagent R-0012 dropwise I could not tell when the change to blue occurred, partly because the color was so pale, and partly because I have trouble telling when purple becomes blue. I tried twice, carefully following the instructions, but no luck. It seems this is pretty much the same kit that I had tried years ago.

Is there anything I can do to make this test easier to read? If not, is there another reliable kit I could use?

Interestingly, I have no trouble with the Taylor TA test (green to red) or matching the colors on the Ph test. In my first season (2004) I did have a chlorine kit that had different shades of yellow that I had trouble matching, so I switched to the DPD powder kit (pink to clear; love this kit!).

Thanks. I appreciate any help/feedback.

*edited to correct color change for TA

[waterbear]

First, the Taylor TA test turns from green to red. If it is turning purple then you have a biguanide (SoftSwim, Baquacil) pool!
The color change on the CH test is from a pink to a sky blue. This document from the Taylor website illustrates this color chagne and info on the color changes of the TA test
http://www.taylortechnologies.com/ChemistryTopicsCM.ASP?ContentID=35

If you are having trouble seeing the color change then add a few more drops of the indicator solution to your sample or try using a 10 ml sample where each drop is 25 ppm CH. TO do so you would add 10 drops of calcium buffer to the 10 ml sample, 3 drops of indicator, and then titrate.
If your color changes to a blue color that reverts to purple (fanding endpoint) you probably have metals in the water (a common interference). If the color has changed from pink to purple then you have not finsihed the titiration and reached the blue endpoint. Remember, if you have high calcium hardness and are using a 25 ml sample size it can take 20, 30, 40, 50, 60, or even more drops of titrant to see the color change to a blue.

The Alex system is designed to maximize chemical sales for your Bioguard dealer and is not to be trusted. IT also uses a strip reader so it cannot give you a calcium hardness reading, only a total hardness reading.

The calcium hardness titration of calcon indicator or one of the eriochrome indicators with EDTA in an akaline solution to remove the magnesium hardness is the standard test for calcium hardness and is the one Taylor uses.

[JimK]

First, the Taylor TA test turns from green to red. If it is turning purple then you have a biguanide (SoftSwim, Baquacil) pool!
The color change on the CH test is from a pink to a sky blue. This document from the Taylor website illustrates this color chagne and info on the color changes of the TA test

Sorry, must have had purple on the brain. You are correct, TA; green to red. We had the pool installed new in 2004 and it has always been a chlorine (via SWCG) pool.


http://www.taylortechnologies.com/ChemistryTopicsCM.ASP?ContentID=35

Thanks for the link. My sample doesn't turn nearly as dark as in the pictures (it looks much closer to #1 than #2). Directly comparing those pictures, I can just make out the difference between #2 and #4.


If you are having trouble seeing the color change then add a few more drops of the indicator solution to your sample or try using a 10 ml sample where each drop is 25 ppm CH. TO do so you would add 10 drops of calcium buffer to the 10 ml sample, 3 drops of indicator, and then titrate.

Thanks, I'll give that a try. So adding enough indicator to get it dark enough doesn't affect the results? I'll also try the suggestions on the Taylor site regarding if metals are present.


If your color changes to a purple color you reverts you probably have metals in the water (a common interference).

I'm sorry, I don't understand this statement.:confused:


The Alex system is designed to maximize chemical sales for your Bioguard dealer and is not to be trusted. IT also uses a strip reader so it cannot give you a calcium hardness reading, only a total hardness reading.

Yeah, I kinda figured as much, which is why I would really like to find a way to test calcium that I can read. I know low calcium isn't an issue for vinyl pools (which I have), but I understand I don't want it too high.

Speaking of the Total Hardness reading, is it possible for Calcium Hardness to higher than Total Hardness? Or is Calcium Hardness always going to be lower than Total Hardness (if so, I'm probably OK given my Total Hardness usually stays around 250ish).


The calcium hardness titration of calcon indicator or one of the eriochrome indicators with EDTA in an akaline solution to remove the magnesium hardness is the standard test for calcium harndess.

Eeeek......what did you just say?:confused: Sorry, that went completely over my head.:o. Are you saying that the Taylor type test is the only reliable one available to me?

[JimK]

....If you are having trouble seeing the color change then add a few more drops of the indicator solution to your sample or try using a 10 ml sample where each drop is 25 ppm CH. TO do so you would add 10 drops of calcium buffer to the 10 ml sample, 3 drops of indicator, and then titrate.
If your color changes to a blue color that reverts to purple (fanding endpoint) you probably have metals in the water (a common interference). If the color has changed from pink to purple then you have not finsihed the titiration and reached the blue endpoint. Remember, if you have high calcium hardness and are using a 25 ml sample size it can take 20, 30, 40, 50, 60, or even more drops of titrant to see the color change to a blue.

Thanks Evan. I see you edited your post (thanks for the clarification) while I was out back trying your suggestion using a 10ml sample. I also used a second tube for reference/comparison (without adding tritate). While the starting color was darker than my original attempt, I still couldn't see the change to blue even after 20 drops of tritate; the two tubes still looked the same to me (since I don't add calcium, I strongly suspect my calcium level wouldn't be that high, ie - 20 drops in 10ml sample = 500ppm). Out of curiosity, I added a couple drops of indicator to each tube to darken the color more, and this time I could see a difference; while subtle, the tube with the tritate added looked blue compared to the tube without tritate (yea!). It seems I can see the difference easier if the color is much more saturated.

So this is what I tried;

1. 10ml water sample in each tube
2. Add 10 drops of buffer to each tube
3. Add 5 drops of indicator to each tube (6 drops helped even more, is this OK?)
4. Add tritate drop by drop to #2 tube only (using #1 tube for reference/comparison)

Doing it this way, although still kind of subtle (I guess my color vision ain't so hot:o) it looked like the pictures on the link you provided. I could see my #2 tube certainly looked blue after 10 drops (adding 1 or 2 more drops didn't change this so I figured I was at the endpoint) giving me a reading of 250ppm at most.

Would this method give me a good result? Or does adding the extra indicator throw off the results?

Thanks again.:)

[waterbear]

Adding a bit more indicator will not affect the results. HOWEVER, if you cannot tell the difference in the color of the 2nd and 4th tube in the picture on the Taylor website then there is something going on with your color vision, although the TA test is usually much more problematic for the colorblind to use than the CH test. The 2nd tube is hot pink while the 4th tube is sky blue. The colors are not even close!
And yeah, the test that Taylor uses is pretty much the standard test for calcium hardness and there test is actually one of the better ones that I have used (and I have tested calcium in both pools and aquariums).

[JimK]

Adding a bit more indicator will not affect the results.

That's good to know. That means I can at least test within the ballpark, and fortunately calcium isn't one of those things I have to check often.


HOWEVER, if you cannot tell the difference in the color of the 2nd and 4th tube in the picture on the Taylor website then there is something going on with your color vision, although the TA test is usually much more problematic for the colorblind to use than the CH test. The 2nd tube is hot pink while the 4th tube is sky blue. The colors are not even close!

If I really look, I can see the difference between tube 2 and 4, but it doesn't jump out at me. Your right, I've known for many years that my color vision isn't normal. Funny that I don't have much problem with the TA test, although I have a theory; with the TA test when it changes from green to red, it appears darker to me along with the color change. With the calcium test, it doesn't appear to get "darker" when changing from red to blue. Perhaps it has to do with the difference in color saturation and/or contrast that explains my vision issue.


And yeah, the test that Taylor uses is pretty much the standard test for calcium hardness and there test is actually one of the better ones that I have used (and I have tested calcium in both pools and aquariums).

That's what I was afraid of. Too bad we don't have a test like the DPD powder chlorine test that goes clear at the endpoint.

I could have a friend who doesn't have problems with their color vision do the test for me.