How to make NO3 and PO4 reference solutions(repost from Left C)

Tom Barr

Founder
Staff member
Administrator
Jan 23, 2005
18,696
747
113
How to Make NO3 and PO4 Reference Solutions

Here's a way to make 10, 20, 30 and 40 ppm NO3 reference solutions:

Add 1.631 g of KNO3 to 1 L DI/RO water. This makes a 1000 ppm NO3 solution. (It's really a 1000.29 ppm solution.)

Add 2 mL of the 1000 ppm solution to 18 mL of DI/RO water. This makes 20 mL of a 100 ppm NO3 solution.

Add 15 mL of the 100 ppm solution to 15 mL of DI/RO water. This makes 30 mL of a 50 ppm NO3 solution.

To make a 10 ppm NO3 solution:
Add 2 mL of the 50 ppm solution to 8 mL of DI/RO water. This makes 10 mL of a 10 ppm NO3 solution.

To make a 20 ppm NO3 solution:
Add 4 mL of the 50 ppm solution to 6 mL of DI/RO water. This makes 10 mL of a 20 ppm NO3 solution.

To make a 30 ppm NO3 solution:
Add 6 mL of the 50 ppm solution to 4 mL of DI/RO water. This makes 10 mL of a 30 ppm NO3 solution.

To make a 40 ppm NO3 solution:
Add 8 mL of the 50 ppm solution to 2 mL of DI/RO water. This makes 10 mL of a 40 ppm NO3 solution.




Here's a way to make 1.0, 2.0, 3.0, 4.0 and 5.0 ppm PO4 reference solutions:

Add 1.433 g of KH2PO4 to 1 L DI/RO water. This makes a 1000 ppm PO4 solution. (It's really a 1000.09 ppm solution.)

Add 1 mL of the 1000 ppm solution to 9 mL of DI/RO water. This makes 10 mL of a 100 ppm PO4 solution.

Add 2 mL of the 100 ppm solution to 18 mL of DI/RO water. This makes 20 mL of a 10 ppm PO4 solution.

To make a 1.0 ppm PO4 solution:
Add 1 mL of the 10 ppm solution to 9 mL of DI/RO water. This makes 10 mL of a 1.0 ppm PO4 solution.

To make a 2.0 ppm PO4 solution:
Add 2 mL of the 10 ppm solution to 8 mL of DI/RO water. This makes 10 mL of a 2.0 ppm PO4 solution.

To make a 3.0 ppm PO4 solution:
Add 3 mL of the 10 ppm solution to 7 mL of DI/RO water. This makes 10 mL of a 3.0 ppm PO4 solution.

To make a 4.0 ppm PO4 solution:
Add 4 mL of the 10 ppm solution to 6 mL of DI/RO water. This makes 10 mL of a 4.0 ppm PO4 solution.

To make a 5.0 ppm PO4 solution:
Add 5 mL of the 10 ppm solution to 5 mL of DI/RO water. This makes 10 mL of a 5.0 ppm PO4 solution.

Left C
 
  • Like
Reactions: Nikolyator

tyska

Junior Poster
Nov 26, 2007
13
0
1
36
Mogi das Cruzes - SP
Tom Barr;18235 said:
Add 1.631 g of KNO3 to 1 L DI/RO water. This makes a 1000 ppm NO3 solution. (It's really a 1000.29 ppm solution.)

Add 2 mL of the 1000 ppm solution to 18 mL of DI/RO water. This makes 20 mL of a 100 ppm NO3 solution.

Hey Tom, doesn't it makes 20ml of a 20ppm solution?!?

We have a 1000ml of a 1000ppm solution, so taking 2ml of it and adding to 18ml of water there should be a 20ppm solution, not a 100ppm solution...
Is it right?!?
Thanks Tom!
Bye!
 

Tom Barr

Founder
Staff member
Administrator
Jan 23, 2005
18,696
747
113
I think the 2's got you here..........

whether it's 2mls added to 18mls of DI, or if you divide by 1/2-> 1 ml into 9 mls of DI water............the dilution is still 1ml of 1000ppm into 10mls total.
Or 2mls of the stock 1000 ppm into 18mls of DI, or 3mls into 27, or 100mls of stock solution into 900mls of DI

Or 1000 ppm to 100ppm, you just made 20s, not 10mls............

You can make 10mls if you want.........

This is just Left C's version.

I think you mixed up 20mls with 20ppm.


Regards,
Tom Barr
 

tyska

Junior Poster
Nov 26, 2007
13
0
1
36
Mogi das Cruzes - SP
hehehe
Yeah, I've got the wrong calcs in here... :D
I refeered 2ml as 200ppm of the solution (don't know the hell why I did it!), but it's still a 1000ppm solution, this 2ml added to 18ml would really be 100ppm! (simple division as it said in the case of 1ml for 9ml) :confused:
I messed the whole thing! hehehehe :eek:
Thanks again Tom!
Bye!
 

Tom Barr

Founder
Staff member
Administrator
Jan 23, 2005
18,696
747
113
well, figuring out what someone else did wrong is often hard, and are if they are right:)

Regards,
Tom Barr
 
  • Like
Reactions: Nikolyator

Crazy Loaches

Guru Class Expert
Nov 20, 2006
103
0
16
Ohio
Just curious if there is a guide based on the use of things like teaspoon, etc... I have a gram/ounce postal scale (up to 5#) but unfortunately it is not accurate enough for this kind of precision. I dont mind if it requires the use of a larger amount of water to get more accuracy (I know its hard to dose 1/64 of a teaspoon or something like that!) but a couple of gallons of DI water from wallmart for 59c is cheaper than buying a new scale.
 

Tom Barr

Founder
Staff member
Administrator
Jan 23, 2005
18,696
747
113
20-30$ ought to give accuracy to 0.01 gram from ebay, you might get 0.001 accuracy for a reasonable amount also.

Regards,
Tom Barr
 

VaughnH

Lifetime Charter Member
Lifetime Member
Jan 24, 2005
3,011
94
48
85
Sacramento, CA
If you want to use weight instead of volume I suggest weighing about 10 teaspoons of each fertilizer, then dividing the weight by 10 to get the weight per teaspoon. The accuracy you could get this way would be limited, partly because measuring spoons are not very accurate. I have maybe 4-5 sets of measuring spoons made of different materials, by different manufacturers. If you have that too, measure a teaspoon using each of those, weigh the total weight of them and divide to get a slightly more accurate weight per teaspoon. Or, to get perhaps a little more accurate, measure using the half teaspoon, teaspoon and tablespoon (3 teaspoons), and do the same.

But, of course, as soon as you buy some more KNO3, KH2PO4, etc. the weight per teaspoon will likely be at least a little bit different.
 

swylie

Prolific Poster
May 23, 2007
35
0
6
Crazy Loaches;22783 said:
So I take it thats a no then on using volume for measurement as opposed to weight.

I guess it depends on how precise you want your calibration solutions to be. There's no need for them to be any more precise than the color key that comes with your test kit unless you're using a spectrophotometer.

If you're feeling really thrifty and have a loose sense of ethics you could certainly buy a digital kitchen scale at Target or Walmart, use it, and then return it. Those scales can be precise to the gram. You only need to make a reference solution once, right?
 

Crazy Loaches

Guru Class Expert
Nov 20, 2006
103
0
16
Ohio
VaughnH;22784 said:
If you want to use weight instead of volume...
Other way around, but thanks for the tips, that might actually work out, just takes some extra testing. I do already have weight per cup measurements, I've calculated out about how many pounds of ferts I would need for a year at my current dosing.

swylie;22786 said:
If you're feeling really thrifty and have a loose sense of ethics you could certainly buy a digital kitchen scale at Target or Walmart, use it, and then return it. Those scales can be precise to the gram. You only need to make a reference solution once, right?

I know exactly what you mean, and I've never done anything like that before;)

But as I stated I have a gram-accurate scale. What this is calling for looks to need maybe a hundredth of a gram sensitivity. I could go out and get a new scale its not really a money issue I guess, I just feel like it’s a waste since I already have a scale that I rarely use, now I would have two.

I guess volume is simply more variable than weight for a reliable measure? If were taking about not using volume because its only marginally more inaccurate than couldn’t we use a larger sample like I mention with a gallon jug of DI water? Lets say what we need happens to be very small and hard to judge by volume, like 1/32 tsp. So then take a larger sample like 1 tsp, put it in a gal, then using something accurate like a 10ml syringe, extract 10 ml out (or whatever it would be to get back down to the 1/32 tsp figure) and start your actual solution. Unless volume is just a lot more variable than I realize.
 

swylie

Prolific Poster
May 23, 2007
35
0
6
Crazy Loaches;22790 said:
But as I stated I have a gram-accurate scale. What this is calling for looks to need maybe a hundredth of a gram sensitivity. I could go out and get a new scale its not really a money issue I guess, I just feel like it’s a waste since I already have a scale that I rarely use, now I would have two.

I guess volume is simply more variable than weight for a reliable measure? If were taking about not using volume because its only marginally more inaccurate than couldn’t we use a larger sample like I mention with a gallon jug of DI water? Lets say what we need happens to be very small and hard to judge by volume, like 1/32 tsp. So then take a larger sample like 1 tsp, put it in a gal, then using something accurate like a 10ml syringe, extract 10 ml out (or whatever it would be to get back down to the 1/32 tsp figure) and start your actual solution. Unless volume is just a lot more variable than I realize.

Shows how much I pay attention... The gentleman already has a scale. Hmm... Well, in that case, consider using the scale to measure your water. At standard temperature and pressure water weighs 1 gram per ml, and your scale is probably much more precise than a gallon jug or a nalgene bottle or glass measuring pitcher. A 10 ml syringe is probably better than measuring 10 grams of water on the scale though.

Your idea of using larger masses and then diluting the samples is called "serial dilution" and it's definitely the best way forward. You can make very precise dilutions with a method like you described, and it allows you to measure in reasonable units: 10 ml, 100 g, etc. I'm sure Tom does serial dilutions in his sleep.

If you use the tools you have and the techniques you described you'll be able to make a reference solution that's more precise than your test kit.

Just remember that a 1:10 dillution is 10 ml + 90 ml = 100 ml, not 10 + 100.
 

Left C

Lifetime Members
Sep 26, 2005
2,500
1
36
69
Burlington, NC
I revised the making NO3 and PO4 reference solutions article that I did a while back. The latest one only requires scales that will measure to two decimal places instead of three like the older version. Also, all you need is one liter of distilled water to make both reference solutions. Here it is:

Directions for Making NO3 and PO4 Reference Solutions III


You will need the following:
- 1 liter of distilled water
- 500 mL graduated cylinder
- 50 mL graduated cylinder
- 1 mL or 3 mL pipette or another measuring device to measure small mLs of solutions
- Scales that are accurate to two decimal places
- KNO3 and KH2PO4 dry fertilizers


Here's a way to make 10, 20, 30, 40 and 50 ppm NO3 reference solutions:

Add 0.70 grams of KNO3 to 429 mL of distilled. This makes a 1000 ppm NO3 solution. (It's really a 1000.72 ppm NO3 solution.)

Add 2 mL of the 1000 ppm solution to 18 mL of distilled water. This makes 20 mL of a 100 ppm KNO3 solution.

Add 15 mL of the 100 ppm solution to 15 mL of distilled water. This makes 30 mL of a 50 ppm KNO3 solution.
* Note: You can use this for the 50 ppm NO3 reference solution.

To make a 10 ppm NO3 solution:
Add 2 mL of the 50 ppm solution to 8 mL of distilled water. This makes 10 mL of a 10 ppm NO3 solution.

To make a 20 ppm NO3 solution:
Add 4 mL of the 50 ppm solution to 6 mL of distilled water. This makes 10 mL of a 20 ppm NO3 solution.

To make a 30 ppm NO3 solution:
Add 6 mL of the 50 ppm solution to 4 mL of distilled water. This makes 10 mL of a 30 ppm NO3 solution.

To make a 40 ppm NO3 solution:
Add 8 mL of the 50 ppm solution to 2 mL of distilled water. This makes 10 mL of a 40 ppm NO3 solution.



Here's a way to make 0.1, 0.2, 0.5, 1.0, 2.0, 3.0, 4.0 and 5.0 ppm PO4 reference solutions:

Add 0.70g of KH2PO4 to 489 mL of distilled water. This makes the 1000 ppm PO4 solution. (It's really a 999.04 ppm PO4 solution.)

Add 1 mL of the 1000 ppm solution to 9 mL of distilled water. This makes 10 mL of a 100 ppm PO4 solution.

Add 2 mL of the 100 ppm solution to 18 mL of distilled water. This makes 20 mL of a 10 ppm PO4 solution.

To make a 0.1 ppm PO4 solution:
Add 1 mL of the 10 ppm solution to 99 mL of distilled water. This makes 100 mL of a 0.1 ppm PO4 solution.

To make a 0.2 ppm PO4 solution:
Add 1 mL of the 10 ppm solution to 49 mL of distilled water. This makes 50 mL of a 0.2 ppm PO4 solution.

To make a 0.5 ppm PO4 solution:
Add 1 mL of the 10 ppm solution to 19 mL of distilled water. This makes 20 mL of a 0.5 ppm PO4 solution.

To make a 1.0 ppm PO4 solution:
Add 1 mL of the 10 ppm solution to 9 mL of distilled water. This makes 10 mL of a 1.0 ppm PO4 solution.

To make a 2.0 ppm PO4 solution:
Add 2 mL of the 10 ppm solution to 8 mL of distilled water. This makes 10 mL of a 2.0 ppm PO4 solution.

To make a 3.0 ppm PO4 solution:
Add 3 mL of the 10 ppm solution to 7 mL of distilled water. This makes 10 mL of a 3.0 ppm PO4 solution.

To make a 4.0 ppm PO4 solution:
Add 4 mL of the 10 ppm solution to 6 mL of distilled water. This makes 10 mL of a 4.0 ppm PO4 solution.

To make a 5.0 ppm PO4 solution:
Add 5 mL of the 10 ppm solution to 5 mL of distilled water. This makes 10 mL of a 5.0 ppm PO4 solution.



Left C

Jonathan;118613 said:
It would be really nice to have this information on the first page :) I had to hunt it down. Its valuable to less experienced people like myself.
Left C;75973 said:
You follow the test kit's direction for testing your aquarium water, if that is what you are testing. If you are testing your tap water, same thing, just follow the directions. Let's call this the sample.

Then the reference solutions are made using "pure" compounds and "pure" water. These give you various color references. Then you compare your sample's color to the reference's color to get an idea of your sample's concentration. It is better to do more than one sample. Do 2 or 3 samples to make sure that the samples are made correctly. If your samples turn out to be different colors, you know that there is an error somewhere. Then you need to find out what is wrong. If all 2 or 3 samples are the same color, you know that either they are made correctly or you made the same, exact error each time.

Make sense?
** Added at Johnathan's request 10-3-13
 
Last edited by a moderator:

Tom Barr

Founder
Staff member
Administrator
Jan 23, 2005
18,696
747
113
I am going to revise this and along with Hoppy's version, sort of a scaleless method, put a nice sticky together for this.

I'd expect to publish it in FAMA at some point, so we will all share the credit.

Thanks,
Tom Barr
 

Tom Barr

Founder
Staff member
Administrator
Jan 23, 2005
18,696
747
113
Left C;42522 said:
Wow! Having two different methods for making reference solutions together is a terrific idea.

Getting bone heads to calibrate when they place so much trust and insistence in telling everyone else they should test is quite another matter:)

Why is this the case for pH meters and not the NO3/PO4?

I just never understood this.
PPs folks love to carry on about testing and measurements and management of nutrients, a few of them actually do calibrate and fewer tell others to do it, "Oh, my API kit is good enough"

Well, EI is good enough in that case as well, so poo poo that and then take short cuts?

I do not get it.

There's a trade off.
Making a simple "how to" so we get reliable accurate results that are verified over the range of interest is how we should do it, otherwise the readings are mere guesses.

12 years ago I knew that was just not going to happen, I still question whether folks will do it most of the time. So using water changes came about in response to this trade off. Now some whine and cry about the water changes.

Damn..........

Cannot win for losing with some folks.

I'll repost Hoppy's and then we can post the sticky.
I'll let you know if the FAMA version is published. I'll need your and Hoppy's permission.

Regards,

Tom Barr
 

mathman

Guru Class Expert
Mar 8, 2011
260
1
18
California
Are these reference solutions like the CO2 4dKH reference solution?

Im sorry if this question is stupid to others but i'm just curious. I was reading the EI target ranges posted by Tom and I would like to know if my tank (55g) is within range. I already have a nitrate and phosphate test kit which comes with a color coded chart to read the levels in the water.

So are the reference solutions mentioned in this thread meant for color comparison like the 4dKH solution? I'm lost sorry :(

And if the the purpose of EI is to have an unlimited amount of nutrients for the plants to use throughout the week, then why be concern about having a NO3 range of 10-30ppm and PO4 of 1.0-2.0 ppm? Are these the optimal ranges?

Thanks.
 
Last edited by a moderator:

Tom Barr

Founder
Staff member
Administrator
Jan 23, 2005
18,696
747
113
mathman;75848 said:
Are these reference solutions like the CO2 4dKH reference solution?

Im sorry if this question is stupid to others but i'm just curious. I was reading the EI target ranges posted by Tom and I would like to know if my tank (55g) is within range. I already have a nitrate and phosphate test kit which comes with a color coded chart to read the levels in the water.

So are the reference solutions mentioned in this thread meant for color comparison like the 4dKH solution? I'm lost sorry :(

And if the the purpose of EI is to have an unlimited amount of nutrients for the plants to use throughout the week, then why be concern about having a NO3 range of 10-30ppm and PO4 of 1.0-2.0 ppm? Are these the optimal ranges?

Thanks.

Yes, you have the idea, but these are much more accurate than the drop checker KH solutions because that requires 2 different parameters to get CO2 in ppm, the drop checkers loose accuracy and assumptions once you use poor colorimetric resolution of the pH solution.

With NO3.......you have only one standard reference to deal with: NO3.
So you compare the KNOWN reference, to the actual color chart to see if the test method/kit is accurate.

You do not have a known CO2ppm however, so checking to see if the pH/KH method you use is accurate is troublesome and hard.
Drop checkers that use 4 KH degrees are targeting a CO2 ppm that is often........too low.
I typically run 45-70ppm of CO2, so a DC is not going to help me unless I adjust it to target a higher CO2 range.

Regarding testing and EI: yes, that is also the point, no need to test, as long as you are adding fish food and not a lot of NO3 is in the tap, nothing to be concerned over.
 

mathman

Guru Class Expert
Mar 8, 2011
260
1
18
California
I'm sorry I just don't understand the next step after making the reference solution. Are we to run two test each time, for example, have the reference solution and the water tank in separate 5mL cylinders and do the test to compare colors?

Thanks.
 
Last edited by a moderator:

Left C

Lifetime Members
Sep 26, 2005
2,500
1
36
69
Burlington, NC
You follow the test kit's direction for testing your aquarium water, if that is what you are testing. If you are testing your tap water, same thing, just follow the directions. Let's call this the sample.

Then the reference solutions are made using "pure" compounds and "pure" water. These give you various color references. Then you compare your sample's color to the reference's color to get an idea of your sample's concentration. It is better to do more than one sample. Do 2 or 3 samples to make sure that the samples are made correctly. If your samples turn out to be different colors, you know that there is an error somewhere. Then you need to find out what is wrong. If all 2 or 3 samples are the same color, you know that either they are made correctly or you made the same, exact error each time.

Make sense?