make my own CYA standard solution?

[camueller]

I was looking for the CYA standard solution on tftestkits.com and didn't see it. This got me thinking, can't I just make my own by adding a certain amount of CYA to tap water?

I'm busy trying to wrap things up as I leave work to go home, so don't feel like mucking around with pool math to figure out how to get a small amount of water to 50ppm CYA, but I'm fairly confident I can make this work. Has anyone else ever messed with it?

 

[JoyfulNoise]

You need 50mg per liter of water. You might find it hard measuring 50mg without a good triple-beam balance or lab-grade digital scale. My suggestion would be to use distilled water to avoid chlorinated/treated tap water.

However, the added acidity of CYA will reduce the pH of the water so you will need to adjust that either by using base demand reagent (R-0006) or calcium buffer reagent (R-0010). Both are sodium hydroxide solutions.

 

[camueller]

You need 50mg per liter of water. You might find it hard measuring 50mg without a good triple-beam balance or lab-grade digital scale. My suggestion would be to use distilled water to avoid chlorinated/treated tap water.

However, the added acidity of CYA will reduce the pH of the water so you will need to adjust that either by using base demand reagent (R-0006) or calcium buffer reagent (R-0010). Both are sodium hydroxide solutions.

Interesting. follow up questions:

1) Am I crazy that I can't find the standard solution on tftestkits.com? is it temporarily out or something?

2) If I did this, how would I know when I had added enough R-006 to get the pH back up to an acceptable range?

3) if R-0006 and R-0010 are both sodium hydroxide solutions, are they interchangeable in all tests?

 

[pooldv]

The standard solution has been taken down from tftestkits.net because people are finding that it reads closer to 40 than 50. Taylor still sells it. Are you crazy? Probably, ask your SO. LOL! :-D

 

[JoyfulNoise]

Interesting. follow up questions:

1) Am I crazy that I can't find the standard solution on tftestkits.com? is it temporarily out or something?

See pooldv's post.

2) If I did this, how would I know when I had added enough R-006 to get the pH back up to an acceptable range?

So what I would do is mix up the 1 L batch. Then I would grab a standard 44mL test volume of the mixture and add R-0004 phenol red. The solution should be acidic. Then add R-0006 drop wise until your solution goes back to normal pH. Record the drop count. Discard the test solution. You now know how many drops of R-0006 it takes to get 44mL of solution back to a neutral pH. I would then mix up a new 44mL batch with the appropriate amount of R-0006 added and use that to test your CYA standard.

You can also do a CYA test on the acidic CYA solution and see what results you get. Technically, the melamine turbidity test should work best at lower pH which is why the R-0013 contains an acid buffer to force the test to lower pH.

Up to you on how you want to do the test.

3) if R-0006 and R-0010 are both sodium hydroxide solutions, are they interchangeable in all tests?

I don't believe they are the same normality so they are not interchangeable.

 

[max2k]

You need 50mg per liter of water. You might find it hard measuring 50mg without a good triple-beam balance or lab-grade digital scale. My suggestion would be to use distilled water to avoid chlorinated/treated tap water.

However, the added acidity of CYA will reduce the pH of the water so you will need to adjust that either by using base demand reagent (R-0006) or calcium buffer reagent (R-0010). Both are sodium hydroxide solutions.

50g can be dissolved in 1 liter of distilled water and then diluted 3 times with factor 10:
1 cup of mix + 9 cups of distilled water = 10 cups of the 1/10 concentration mix, repeat this 3 times. Measuring initial 50g or 1L might still be a challenge.

 

[JoyfulNoise]

50g can be dissolved in 1 liter of distilled water and then diluted 3 times with factor 10:
1 cup of mix + 9 cups of distilled water = 10 cups of the 1/10 concentration mix, repeat this 3 times. Measuring initial 50g or 1L might still be a challenge.

I thought about that too but doing serial dilutions can add a lot of error. With wet chemistry like this, one really needs good, chemical glassware to do the job right. You'd need a couple of different graduated cylinders and some Erlenmeyer flasks. Accurate bulb pipettes are great but pricey.

Using basic kitchen type measuring cups is too crude and will introduce a lot of errors.

 

[max2k]

I thought about that too but doing serial dilutions can add a lot of error. With wet chemistry like this, one really needs good, chemical glassware to do the job right. You'd need a couple of different graduated cylinders and some Erlenmeyer flasks. Accurate bulb pipettes are great but pricey.

Using basic kitchen type measuring cups is too crude and will introduce a lot of errors.

true in general but if you're after simple fraction dilutions and can live with 10% error you could use the same cup with whatever volume it happens to have. As long as you don't go into mL, grams, etc It gets more difficult with each step: to stay within 10% total error you need to be within 3% on each of 3 steps: 0.097^3 = 0.00091, 9% error. Kind of pushing.

 

[camueller]

@pooldv lol, ok, yeah, i'm part crazy. I guess I could have answered that myself I'd been reading threads about people finding it off, but I didn't realize they took it down from the site because of that. All the talk about finding the right light to do the test is what made me want to buy some standard solution.

I have a digital scale that is fairly accurate to .1g. I figure I can measure out a 5g sample of CYA to mix with the 1L of water. Perhaps I could even do 2L and 10g of CYA. Then do the ph testing as you say. I like that method.

This may not be super accurate in the end, but it sounds like an interesting experiment, so I'll probably go for it.

One last question...would RO filter tap water be ok in place of distilled? Not that distilled water is expensive, I just have a spigot of RO filtered water in the kitchen.

 

[max2k]

RO should be fine provided it works as expected.

 

[camueller]

Thanks. It does. I'll test it before I do this just to be sure.