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