titration end point

jduong916 · Nov 14, 2017

when do you stop? is it when the color just starts to change? is it when the color looks like the card?

Randy Holmes-Farley · Nov 14, 2017

What type of kit are you asking about?

jduong916 · Nov 14, 2017

Red sea alk test, salifert calcium

jduong916 · Nov 14, 2017

The red sea alk test never really looks like the color on the card though

PatW · Nov 14, 2017

I use the Red Sea Pro test. The indictor/titrant starts out as blue turning increasingly yellow as you add titrant. The point is when you first reach a green with a yellow tint. It happens right after you lose the green with a blue tint. At least, that is the way I read it.

spiraling · Nov 14, 2017

PatW said:
I use the Red Sea Pro test. The indictor/titrant starts out as blue turning increasingly yellow as you add titrant. The point is when you first reach a green with a yellow tint. It happens right after you lose the green with a blue tint. At least, that is the way I read it.

That's how I read it too on the same kit - but its still a valid question. If I go until it is bright yellow bordering on orange instead of green that is about 1dkh higher. I know I have stable alk, but I'm not sure if it is 9 or 10.

Scott.h · Nov 14, 2017

jduong916 said:
Red sea alk test, salifert calcium

Not that triton is the "be all end all" test for calcium. But a Salifert full color change seems to reads low. I always figured a full change minus one drop should be accurate. Basically if I'm around 390-400 Salifert with a full color change, I'm good at about 430-440 triton, which may be inaccurate also.

jduong916 · Nov 14, 2017

spiraling said:
That's how I read it too on the same kit - but its still a valid question. If I go until it is bright yellow bordering on orange instead of green that is about 1dkh higher. I know I have stable alk, but I'm not sure if it is 9 or 10.

Same here. My alk is stable, but its between 7.5 and 9. Who knows what it really is lol.

Tigweldpro · Nov 14, 2017

I have always wondered this with the Redsea pro calcium test. It starts red and then turns purple then dark blue. The card shows blue as finished but I don't know
There new pro alk test goes from blue to green and if you go too far it goes yellow so that test is easy to know when your done.

PatW · Nov 15, 2017

From my reading, as long as your DKH is within a certain range like 8-14, you are fine. The main thing is keeping your DKH relatively constant. The Red Sea test is sensitive to about .3 DKH so it is good for monitoring stability. I know if my tank has gone down some and that I need to add ALK. It is just that I am not that sure as to what my exact DKH is. It might be 8.7, but then again, it might be 9.5. My Salifert test does give a higher number. API gives about the same answer but API only measure DKH in whole numbers.

Now, when I worked in a lab, I always made up standards and ran a standard curve on every piece of equipment I had. I would think that Randy could tell us how to make a 9.00 DKH standard ALK solution so we could calibrate our tests. But I don’t know if it is worth the effort.

nkyreef · Nov 15, 2017

Determining the correct reading for the Red Sea alk pro test kit is difficult. The color change is so subtle unlike the Salifert which I think is easier to see. However my Salifert always read high. Here's a comparison of 2 readings a month apart.

1st
Red Sea = 7.84
Salifert = 9.28 dKH
API = 8 dKH

2nd
Red Sea = 8.82 dKH
Salifert = 10.08 dKH

Randy Holmes-Farley · Nov 15, 2017

The reason I asked the type of kit is because what is happening at the color endpoint is different in different types of kits. In a calcium kit, there is still calcium being counted as long as the color is changing shade (not just getting weaker (less intense)in the same shade), but in an alkalinity kit, the kit is aiming for a particular pH, and the color can keep changing as you pass by the exact endpoint. They try to make it as tight as possible, but it is not a perfectly sudden endpoint.

Generally, follow the instructions and/or color indication (even look online for videos) for the exact color, especially in a pH kit.

For example for Red Sea Calcium and alkalinity:

Tigweldpro · Nov 15, 2017

Whoa, blast from the past.... is that you in the videos Randy?
I haven't been able to find a video for the new KH kit as it goes from blue to green to yellow.
Note taken: Cal needs to be blue not dark purple.

Thanks

redfishbluefish · Nov 15, 2017

With any color changing titration, it's over when one more drop no longer changes the color. So when you think you are at the end, read the syringe, then add one more drop. If no change, go with the reading before adding the drop. If continued change, read the syringe again and repeat one more drop.

Randy Holmes-Farley · Nov 15, 2017

Tigweldpro said:
Whoa, blast from the past.... is that you in the videos Randy?
I haven't been able to find a video for the new KH kit as it goes from blue to green to yellow.
Note taken: Cal needs to be blue not dark purple.

Thanks

lol, no, not me.

TMB · Nov 15, 2017

These color change tests drive me crazy as well since I don't seem to be able to see the color well. Once I found Randy's PH probe method of alk testing, I've used it ever since. Much easier to watch the PH meter and then read the amount of acid that was added. The math is also easy to remember once you do it a few times. Thank you @Randy Holmes-Farley for the article explaining it!

Now we just need an alternate method for the rest of the important tests. I guess Hanna is the next option.

Scott.h · Nov 15, 2017

I was a automotive painter for 17 years, always tinting paint. What I've found is most males are color blind to an extent in one area or another. Definitely not uncommon. Many don't realize it. Women can generally see color better then males for some reason. If I'm questioning myself I ask my wife's opinion to see if it matches my opinion.

Tigweldpro · Nov 15, 2017

Scott.h said:
I was a automotive painter for 17 years, always tinting paint. What I've found is most males are color blind to an extent in one area or another. Definitely not uncommon. Many don't realize it. Women can generally see color better then males for some reason. If I'm questioning myself I ask my wife's opinion to see if it matches my opinion.

Then she says "remember when i asked you to look at the paint samples when we were painting our room and you said i dont care"....... I dont care....

Scott.h · Nov 15, 2017

Tigweldpro said:
Then she says "remember when i asked you to look at the paint samples when we were painting our room and you said i dont care"....... I dont care....

Eh, actually it was me alone at Home Depot trying to decide which shade of gray to go with. (There's a joke in there somewhere). The important thing wasn't the paint. It was that I finally had a tank in my bedroom wall!

aeras1131 · Nov 15, 2017

I do not know the answer to that question I use Salifert Mg test kit, and the titration point for that test is very clear. I look for the first change shake. I look for the second change shake. Typically the third color change and shake is the titration point for me. It is very clear on this test. There is not a gradual color change.