Resource Testing Protocol for SN: With Aquarium test strip 0, 1, 5, 10 ppm

[Daisy88_99]

Hi, guys. Here is a detailed breakdown of how I plan to test my SN when it arrives. Some important things to note is that an aquarium strip test is not precise but no at home test ever will be unless you are an expert. I enjoyed making this until I found out about the"Molar Mass Controversy", that was a headache to sit through because I like to think I am pretty decent at chemistry but I still don't know 100% what the correct thing to do is.

I talk more in dept about this below after the testing protocol and I linked some threads covering this in full so please look at those if you are concerned. I came to the conclusion that Molar Mass is not needed for this because in short, the law of conservation of mass says mass is never lost and I understand the argument. However, the fact that of the matter is that 1 mole of SN will always produce 1 mole of nitrite ion so the molar mass doesn't apply here. Please feel free to correct me if you think I am wrong about ANYTHING on this post as I always intend to give factual information to the best of my knowledge.

This testing protocol is mostly based on jake3d's write up as mentioned in the thread under "Reference", I tried to make this post as clear as possible and you may be able to swap out variables for your experiment once you somewhat understand it, because you may not have all the equipment needed. (But they are very use to get and pretty cheap imo)

Aquarium test strip 0, 1, 5, 10 (ppm = mg/L) Testing Protocol for SN
Equipment
- Graduated Measuring Cups: 1000ml, 500ml, 300ml palstic measuring cups
- Stainless Steel Syringe: ≥0.1 mL increments
- Precision Pocket Scale: 0.1 g accuracy
-Coffee Filter Paper/Large Coffee Filter Baskets or Lab Weighing Boats or Paper (something reliable to put SN on to put on the scale)
- Stirring rods and spoons

Step 1: Make Stock Solution
cup = 1000ml = 1 liter
SN = measure 2.5g of SN on the scale using a Coffee Filter
- put 2.5 g of SN in the cup and fill to 1000ml

Concentration of the Stock = (mass of SN in mg) / (volume in liters) = (2.5g*1000 = 2500mg) / (1000mL/1000= 1L) = 2,500mg/L - will give max reading (10ppm)
- stir and fully mix with the rod

Step 2: Make Test Solution
Goal: Bring concentration down from 2,500mg/L to 5mg/L so it' in the middle
cup = 500ml
- Syringe transfer = put 1 mL from stock to second 500ml cup
- add 499 ml of water in the cup after the stock (500ml total 1mL from stock + water)

2nd solution = (Cstock * stock volume added) / 500 ml = (2,500mg/L * 1mL) / 500ml = 5 mg/L (perfect)
- stir and fully mix with the rod

Step 3: Test Purity
- Dip the aquarium strip into the final 5 mg/L solution.
- If it reads 5 mg/L, SN is nearly 100% pure, theoretically. Doesn't account for errors, strip test inaccuracies, and other things!
- If significantly lower → SN <100% pure.
- If significantly higher → error in preparation or test strip.

Step 4: Optional Second Test to get 1 ppm: WAY LESS accurate unless you have a really good scale that can actually measure 0.1g properly

Make new stock solution with 500ml cup:
cup = reuse the 500ml cup, make sure you rinse it out.
SN = measure 0.1g of SN on the scale using a Coffee Filter
-put 0.1 g of SN in the cup and fill to 500ml
Concentration of the Stock = (mass of SN in mg) / (volume in liters) = (0.1g*1000 = 100mg) / (500ml/1000= 0.5L) = 200mg/L - will give max reading (10ppm)
- stir and fully mix with the rod

Make Test Solution:
Goal: Bring concentration down from 200mg/L to 1mg/L
cup = 300ml but we only need 200ml
- Syringe transfer = put 1 mL from stock to second 300ml cup
- add 199 ml of water in the cup after the stock (200ml total 1mL from stock + water)

3rd solution = (Cstock * stock volume added) / 200 ml = (200mg/L * 1mL) / 200ml = 1 mg/L (perfect)
- stir and fully mix with the rod

Test Purity:
- Dip the aquarium strip into the final 1 mg/L solution.
- If it reads 1 mg/L, SN is nearly 100% pure, theoretically. Doesn't account for errors, strip test inaccuracies, and other things!
- If significantly lower → SN <100% pure.
- If significantly higher → error in preparation or test strip.

Reference:

SN aquarium purity testing

This is based on @jake3d 's write up, but aims to get results around the *middle* of the test range. When we get results at the edge of the range, eg the max, it may leave us questioning the accuracy, eg was the true value higher than the max (eg due to a mistake with the test method), but can't...

sanctioned-suicide.net

Molar Mass Controversy
You can find exactly what I am talking about in these forums: https://sanctioned-suicide.net/threads/problem-with-sn-testing-information.197364/ and https://sanctioned-suicide.net/threads/a-possible-flaw-in-vizzys-calculations.232937/.

I think understand the argument. SN has a molar mass of around 69g/mol and the nitrite has a molar mass of *46g/mol so 46/69 =*0.67 times 100 is 67%. Therefore, the nitrite is only about 2 thirds of the weight we measured on the scale. SN dissolves in into Na+ and NO2-, we get 1 of each ion so 1 mole of SN produces 1 mole of Na+ and 1 mole of NO2-. If we could take out all the Na+ from the solution then yes, the result would be only 2 thirds of the weight.

However, for our purpose of testing it in a aqueous solution, I think we don't need to account for the molar mass. That's elemental analysis, combustion chemistry or theoretical composition problems, and things like these don't really apply in this case. I remember studying molar masses in school and I vaguely remember only worrying about things like that in theory and not in practice like in a dilution. But I am NOT an expert.

Mass does not determine ion availability, Moles determine ion availability. Since we get 1 mole of each, we can ignore the molar mass. It would only come into play if the moles were different. Please correct me if I am wrong because I used Ai to wrap my brain around some of this. This looks simple on paper like of course nitrite is only 2 thirds because the chemistry says it but In practice, chemistry doesn't really behave how you would expect it to. I couldn't find any real life sources using molar mass to determine the purity of any salt like SN. Chatgpt gave me this source that is hard to understand but it seems like they are doing a experiment on Nitrite and Nitrate, they don't seem to be accounting for molar mass: http://monitoringprotocols.pbworks.com/w/file/fetch/21630051/EPA353_2.pdf

 

[peacebenow]

this is bringing me back to organic chem, biochem et al. my brain is too tired to even go there. good luck. I hope it is pure and good.

 

[Surek]

Mass does not determine ion availability, Moles determine ion availability. Since we get 1 mole of each, we can ignore the molar mass

The thing is, test strips don't measure concentration in mol/L; they measure it in mg/L or ppm. That means they measure the mass of the target substance (the NO2- ion in our case). The test pads react to the physical weight of the ions, not the moles

The exact same logic applies to that .pdf file you linked:
They take 7.218 grams of KNO3 and 6.072 grams of KNO2 precisely because that's exactly what it takes to get 1 gram of pure Nitrogen

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Example:
Let's say that to get 1 mg/L of NO2-, we need exactly 1000 NO2- ions, which together weigh exactly 1 milligram. To give the strip those 1000 ions, we need to add 1000 molecules of the salt (NaNO2) to the water. Since we're dropping in 1000 molecules, the "1-to-1" reaction is perfectly maintained. BUT, because of the heavy sodium in the salt, those 1000 NaNO2 molecules actually weigh 1.5 milligrams

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Molar mass of Sodium Nitrite (NaNO2): Sodium (23) + Nitrogen (14) + Oxygen (32) = 69 g/mol
Molar mass of the target Nitrite ion (NO2-): Nitrogen (14) + Oxygen (32) = 46 g/mol
Ratio of the mass of the entire salt to the mass of the required ion: 69 / 46 = 1.5

That means if you weigh 1 gram of NaNO2 your solution gets only 0.67 grams of actual NO2-. Or, to get 1 gram of NO2-, you must weigh 1.5 grams of the salt (NaNO2)