Test kit drop at a time - shortcuts OK?

[BigJPDC]

Hello - sorry if this is lame, but I am using the calcium test from the API 'reefmaster' test kit, and basically what you do is add one drop of reagent #2 until the sample color changes. Each drop is equal to 20 mg/L. So to get to a reading of 480, you would have to add one drop and shake, repeating 24 times.

That is really a pain in the neck, sorry.

So before I invest in an electronic test device, as I just did for pH, can I just cut to the chase and add 10-20 drops at a time before moving to the one-at-a-time part? Getting the proper reading is obviously more important, so if this is a bad idea, I'd rather use another kit.

The dKH test is only going to take 8-12 iterations, so isn't quite as brutal but again, if I could drop the first seven in at once and go from there, it would speed things up.

thank you,
jp

[the3kgt2]

I have the same calcium test kit and i normally add 18 drops, then start shaking after each drop after that.

[BigJPDC]

It's really a killer, isn't it? I hate it that the margin of error, depending on whether or not I see the change from purple to blue (!) is thus 40. Seriously purple to blue? The dkh test is a no-brainer as you go from blue to yellow.

I guess you could just add 20 and if it's still purple then you are over 400. =(

[Randy Holmes-Farley]

Yes, it is fine with such kits to blast ahead to a point just shy of the endpoint, let it mix in a bit, then finish off carefully. :)

[BigJPDC]

thank you Randy, very cool.

Hey, while I have you - is there any way to get more precise readings by altering the amount of sw in the test vial? Like if I used 10ml instead of 5ml and doubled the number of drops, could I get calc down to an incriment of 10, instead of 20?

jp

[JohnnyM2]

Why do you need it to be that accurate? Any way you would just need to double the number of drops and get the same accuracy. Have you thought about buying a Ca meter? $$$$$$

[BigJPDC]

just asking johnny - why not be accurate?

[Randy Holmes-Farley]

For some kits that will work, as long as you can still distinguish the colors. Alkalinity, for example, may work out. But not all will have an especially sharp endpoint, and you may just increase the uncertainty of where you "call" the endpoint.

[BigJPDC]

got ya. I really don't like this test kit except for the dkh test. I was hoping that I could lessen the amount of error by doubling up but if it will become more difficult to discern the gradients of purple\blue than that is a bad idea.

Now that i have my digital pH device, I feel much better knowing that I am at 8.29, instead of some shade of red between 7.6 and 8.4. I'd like to have that same kind of certainty with calcium.

cheers,
jp

[Randy Holmes-Farley]

:thumbsup:

Happy reefing. :)