Reefmaster Test Kit... How blue is blue?

M

MHG

Active member
I have the Marineland reefmaster test kit. There are no color cards and the calcium and alkalinity tests require you to add drops until you achieve blue. Well I kept adding and adding and at about 42 drops it looked blue but if I held it up to the light is was still slighly purple. Well that puts my calcium at 630 (new tank and still cycling) and I probably could have added more drops.


On the alkalinity test just 4 dropps and I am blue...


So has anyone had any experience with this kit?
 
This is a titration. The actual color or hue of blue is unimportant, and will be different sometimes. What you are looking for is the first appearance of a color change. The first little blue tint that persists on stirring.

I'm not real familiar with that particular kit. I assume it starts off pink before you add the drops? In that case, if it turned purple (blue + red/pink = purple) then you would stop there since that is the appearance of some blue. Basically, anything bluer than pink.
 
MHG said:
I have the Marineland reefmaster test kit. There are no color cards and the calcium and alkalinity tests require you to add drops until you achieve blue. Well I kept adding and adding and at about 42 drops it looked blue but if I held it up to the light is was still slighly purple. Well that puts my calcium at 630 (new tank and still cycling) and I probably could have added more drops.


On the alkalinity test just 4 dropps and I am blue...


So has anyone had any experience with this kit?
Click to expand...

Are you sure that is a Marineland Reefmaster test kit and not API? I never seen Marineland make testing supplies. Not say they don't but there not on their website.
 
I stand corrected, wonder why I didn't find that on there website. I was looking for a PDF manual to see what it said.
 
When I was using the IO calcium test kit, I found that I had to wait for a minute after the first hint of blue (actually, it was purple) to allow the reaction to proceed. Then, another drop or two would finish the titration. With that procedure, the test matched my Salifert to within a drop. Your kit might need a similar delay, depending on its design.

What brand of salt are you using, and what is the SG? Has the SG device been calibrated with a seawater standard?
 
disc1 said:
This is a titration. The actual color or hue of blue is unimportant, and will be different sometimes. What you are looking for is the first appearance of a color change. The first little blue tint that persists on stirring.

I'm not real familiar with that particular kit. I assume it starts off pink before you add the drops? In that case, if it turned purple (blue + red/pink = purple) then you would stop there since that is the appearance of some blue. Basically, anything bluer than pink.
Click to expand...

Wow thats real subjective... I think its time for a better kit
 
MHG said:
Wow thats real subjective... I think its time for a better kit
Click to expand...

Not subjective at all. It's a titration. The best kits work that way.

Basically you have an indicator in there that is going to be one color when the analyte is present and a different color once you've reacted it all up. The important thing is the change in color. As soon as the color isn't what you started with, stop.

It's not like the colorimetric tests (where you read a color off a chart to get the answer) at all.
 
Well, I had my 2 kids each do a test. They both came up with a different amount of drops to say "it is blue" there is pink just turning blue, more blue than that but still some pink, blue but purple when you hold it to the light and blue...

http://www.youtube.com/watch?v=VT9tEHp828w


Here is a video of the red sea calcium kit. At 3:46 into the video it just turns from its original color. at 4:01 it just starts to turn blue IMO, at 4:11 it is blue, later in the video he tells you "this is the color you are looking for..." To me that is subjective. but I can work with Blue, with no purple as shown on that kit. True a different kit, but looking for some guidance.

When I reach that color blue I am at 630 ppm... still cycling, no life in the tank. Sounds high to me and thus my question of color.
 
As a practicing analytical chemist, I am not real thrilled about the instructions from red sea. In truth, a titration is over at the point you release your analyte from the indicator. From the story you relate, you should be stopping way before you get to what satisfies you as blue.

The color should stay its original pink for the first few drops, then when it changes you are at your end point. You are relying (usually in the case of a calcium test) on zinc or magnesium to turn your indicator, so the exact color you get may differ.

Go look for a recent thread by me on how to get accuracy from test kits. Id give you a link but I'm on my phone. The first few paragraphs explain the chemistry of such a test as it relates to a magnesium determination. If you want, I can go into further detail on the determination of calcium.

EDIT: Here's a link to that thread. http://www.reefcentral.com/forums/showthread.php?t=2078493
 
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Besides, unless you have been adding a whole bunch of calcium supplement to this water, you know 630 is off the mark.

Try this. Record the number of drops and what that would get you for calcium at each of those points you determined. First change, purple, bluer, pure blue. Let's see what those other results would have been. They're definitely going to be much more realistic numbers, unless you've been dumping shovels full of calcium chloride into your tank.


And be sure to stir between drops.
 
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