reading Salifert NO3 test

[kevensquint]

Hello, I normally used the RSpro NO3 kit, but the LFS was out. So I tried the Salifert, nice and simple. One thing tho, if I look down into the test vial its about 10ppm. If I look through the side of the vial its about 0.25-0.50ppm. I know my tank runs low, normally. But how can we be sure which resolution to use? If I test a friends tank, I wouldn't know which range to use.

 

[JimWelsh]

If you get a reasonable reading on the low range, then use the low range.

 

[UK_Pete]

I dont understand this. If you look through the side of the vial, do you are looking through about an inch of liquid, the color should be much darker than if you are looking from the top of the vial, where you only have about 1/8th of an inch liquid to look thorugh. Thats how the 2 different 'ranges' are meant to work, when you look through a longer distance of liquid you are making the color more intense. You have a high difference between these 2 readings, you are meant to divide the reading by 10 if you look thorough the side of the vial, I am not sure if you are doing that already. Can you take a piccy looking through the side and from the top and post it?

BTW when you look through the side, you are meant to look from one wall of the vial to the other wall, its a thin layer of liquid you look through sideways. You should not look through the base of the vial if you are doing the 'side to side' reading.

 

[kevensquint]

OK, yes I understand the idea. In fact looking at my reference color slide, I know what's wrong. The changing point from high range to low range is the 10ppm color when looking down into the vial. Well my sample is right around the 10 color. But to my eyes it looks like it may be the 25ppm color or somewhere in between... I can't see a clear winner between those two colors compared with my sample color.

 

[glb]

You only look for it from the side if looking from the top is too pale to get a reading. I've always wondered if you were supposed to put the vial on the card or just above it. That changes the color too. I can't tell from the directions.

 

[jduck]

Use the side view and take cell pic with card behind it.

 

[kevensquint]

Well I guess the issue is my eyes. But here is my test...So do you agree with 0.50 ppm ?

 

[saltyphish]

That would indicate 5 ppm

 

[saltyhog]

That looks like 5 both ways to me. Were you dividing by 10 on the side view or 100?

 

[kevensquint]

Ah yes, thanks.. Was dividing by 100 instead of 10.

 

[UK_Pete]

Re how to look through it, I always wondered that too. If you put the vial right up against the card then the light goes through it twice so will read higher (more colored) as the light path through the dye is double. For that reason although I never checked with Salifert I put the card at a 45 degree angle so the light hits it directly from the window / light bulb, then look through the vial at the white card, holding the vial just above the colored patch on the card. Whether thats right or not I dont know though.