Calibrating Test Kits - for non-Chemists

[handyguy42]

I m really happy..I appreciate the work you put into this. I don't have an accurate scale to use other described methods, so this is making my day thanks all...

[houstonhobby]

Hoppy,

I really appreciate this post. I don't understand the part about doing the calibration every time I use my kit. If I am using an API kit with little bottles of drops, what makes the kit results drift so much from week to week? Just asking for information you understand. I don't have the knowledge necessary to critique your statement.

Also, could I save the test tubes where I did the test, and use those to compare my colors against, instead of using the card that came with the test kit?

Thanks,
Rod

[Hoppy]

Oops, I'm very late seeing this. Sorry!

It isn't that the test kit results vary from day to day, it is that they are made with organic chemicals, with organic dyes, and those are not stable chemicals. Eventually they deteriorate. So, if your test kit sat on the dealer's shelf for a year before you bought it, or if the dealer allowed his store to get very hot for a few days, like over the weekend, the kits may never be accurate after you buy them. Then, if you are like me, you buy the kit, stash it under the aquarium and when you finally use it, you don't remember how long you have had it, so it may deteriorate on your shelf too. Now, add to that, that these are very cheap kits, so it is highly unlikely that there is good quality control on their manufacture.

Even if none of the above apply to you, just remember that professionals who do testing of any kind always calibrate their test equipment before use, or, at a minimum every few months. And, that calibration is done with an accuracy far better than the test equipment is designed to meet. No one who is paid to test things ever uses anything for measurements unless it is calibrated first and often. Even professional mechanics get their vernier calipers calibrated on a routine schedule.

[wespastor]

Thread Resurection!!!!!!


Any new calibrations???

Thanks,
Wes

[plantbrain]

Ho hum............calibrated test kits for nutrients which are among the easiest things to add.....but not CO2 calibrations, light? Well, folks need a PAR meter, and reference bulb and distance, but light calibration is fairly easy as well.

Still, why do folks spend a lot of time, energy, $, effort etc on ferts, and not on light or CO2? Wanna be all precise and Scientific with ferts, then wing it with CO2/light?

My point is that light and CO2 are much larger factors in management. The same types of calibration rules apply to their measure that do to Test kits for NO3. Once CO2/light are correctly addressed for a management goal you have, then nutrients are really easy and have much less impact.

Still, folks should calibrate whenever they can if they want to feel the results are actually correct. If you prefer to guess, then why bother testing at all?
Do not even bother, do a decent water change and move on.

Better than guessing and not doing anything.

Regards,
Tom Barr

[Aquaticz]

Hoppy to the rescue :-)
Well you have done it again _ thank you

[Hoppy]

Originally Posted by wespastor

Thread Resurection!!!!!!


Any new calibrations???

Thanks,
Wes

None, and I don't expect to do any additional ones. Remember, the only purpose for doing this type of calibration is to find out if your test kit readings mean anything. The accuracy you can get this way is very limited. But, it is better than thinking your tank has 50 ppm of PO4 in it, when it really has less than 4 ppm. I don't use test kits at all now, and never did make much use of them, so this was mostly just a challenge for me. I did try to make 4dKH water using the method here, and it measured 3 dKH with my test kit. So, that "proves" that either this calibration method works, but with crude accuracy, which is what I aimed for, or it proves that my KH test kit readings are off. Being an optimist, I assume the former

[sbailiff]

Thank you for this awesome calibration. I just think that it is still a little baffling to me. I don't know where to get No3 or the phosphate test product. Is there some obvious source? I am sorry for sounding stupid.

Thank you. Steph

[max chavez]

ahhhhhh......what conflicting emotions I had this afternoon, when, after testing nitrates with a 'new' test kit for the last several months and not agreeing with the results, I picked up a galllon of distilled water and made some test solutions! Luckily, the results were very easy to read:
Tank water: yellow
10ppm standard: yellow
25ppm standard: yellow
50ppm standard: yellow

All exactly the same shade even! It was so simple! Now I know that my water is probably kinda close to 10-50ppm +/-50 or so. Thanks API/retailer

(and thank you Hoppy, for making the procedure so user friendly-no sarcasm)

I guess I'll just stick to those water changes, who knew?(well, Tom, I guess)

[Whitebeam]

This looks supurb, and is probably just what I need to help resolve the difference between my tap water (25ppm Nitrate) and the time for a critical water change (50ppm? Nitrate). Two questions please:

1) Can the reference solutions be kept for a few weeks, or will the colours deteriorate?

2) Any chance that somebody could translate the measurements in the recipes into SI units? Many of us don't use cups as volume measures and don't use volume measures (teaspoons) to precisely measure chemical powders.

Edit: Trying to answer 2) myself. Presumably the 'cups' used in the recipes are US cups, i.e. 236.6ml. Now, all I need to do is work out the weight of a teaspoon on Potassium Nitrate (etc)

Peter

[Hoppy]

Originally Posted by Whitebeam

This looks supurb, and is probably just what I need to help resolve the difference between my tap water (25ppm Nitrate) and the time for a critical water change (50ppm? Nitrate). Two questions please:

1) Can the reference solutions be kept for a few weeks, or will the colours deteriorate?

2) Any chance that somebody could translate the measurements in the recipes into SI units? Many of us don't use cups as volume measures and don't use volume measures (teaspoons) to precisely measure chemical powders.

Edit: Trying to answer 2) myself. Presumably the 'cups' used in the recipes are US cups, i.e. 236.6ml. Now, all I need to do is work out the weight of a teaspoon on Potassium Nitrate (etc)

Peter

I admit I didn't give any thought to the rest of the world where "cups" and "teaspoons" are not easy to measure. All I wanted to do was make it easy for someone with a typical American kitchen to determine if his/her test kit reading meant anything at all. A similar approach could be taken with common metric measuring equipment. I will leave it to you to enjoy working that out

[Whitebeam]

Originally Posted by Hoppy

I will leave it to you to enjoy working that out

A challenge! This is taking me back 28 years to my O-Level chemistry class - wow. Check my rusty theory here and then I'll try to work out 'kitchen' units later on ...

Looking at your NO3 example (1/4tsp in 4 cups):

800ppm NO3 = 800mg/l NO3
Molecular mass of NO3 = 62.0, molecular mass KNO3 = 101.1
So: 800mg/l NO3 is equivalent to 800 x (101.1/62.0) = 1304.5mg/l KNO3

If this is right, and 4 cups = 946.4ml, then:

Your 1/4 tsp KNO3 should weigh: 1304.5 * (946.4 / 1000.0) = 1234.5mg

Did I get it right, teacher?

Peter

[Hoppy]

Originally Posted by Whitebeam

[/INDENT]Did I get it right, teacher?

Peter

Unfortunately I didn't keep my scratch pad calculations. As I recall I used a round number for the mass of the fertilizer chemicals per teaspoon. It may have been 4 grams or 5 grams, but I can't recall for sure. So, I don't know if you got it right. It does look like you are using the right logic, so it is probably right.

[ar0wan]

Originally Posted by max chavez

ahhhhhh......what conflicting emotions I had this afternoon, when, after testing nitrates with a 'new' test kit for the last several months and not agreeing with the results, I picked up a galllon of distilled water and made some test solutions! Luckily, the results were very easy to read:
Tank water: yellow
10ppm standard: yellow
25ppm standard: yellow
50ppm standard: yellow

All exactly the same shade even! It was so simple! Now I know that my water is probably kinda close to 10-50ppm +/-50 or so. Thanks API/retailer...

The bottle labeled #2 is not extra solution
it must be combined with #1 per the instructions to give correct readings

[dobie832]

The calibration solutions are usless as you used volume/volume. The volume of water will vary based on temp and the spoons of dry ferts can vary due to compaction differences. Any good lab will use weight/weight as they do not change.I suspect your solutions could vary by as much as 20%