Discussion Problem with SN testing information

[TurboCharcha]

I'm making this post because I'm worried that people might be testing their SN wrongly. If I'm right, then tests done with the method explained in the SN bible (and everywhere else I have found on this site) will lead to an underestimation of the tested SN purity. This, in turn, may worsen people's anxiety about their CTB, or maybe lead them to increase the dose of SN they ingest (because they could think their SN is less pure or effective than it actually is), possibly increasing the chance of vomiting. In this post, I explain what I believe is missing from the testing procedure, but I'll repeat it here in more detail because I think it is really important. The post said:

Hey, I noticed something that is really important and I don't see being considered: test strips and kits measure concentration of nitrite ions (NO₂⁻), not sodium nitrite (NaNO₂). So this testing method should account for the proportion of nitrite in sodium nitrite. The molar mass of NaNO₂ is about 69 g/mol, while the molar mass of NO₂ (and of NO₂⁻ because the mass of an electron is negligible compared to the mass of protons and neutrons) is about 46 g/mol. Therefore, the actual mass of NO₂⁻ that you are putting into the water is 46/69=0.666 times the mass of NaNO₂ that you weigh on the scale.

I want to emphasize that the result one would get without accounting for the dilution of SN (i.e., using the method in the SN bible) would be wrong! In fact, it would be about one third less than what one would expect with a 100% pure SN. For example, if you dissolved 5g of SN into 1L of solution, then extract 2mL from that solution and dilute it to 1L, you would have a concentration of 10mg/L of NaNO₂ (SN), but the concentration of nitrite ions (NO₂⁻), the actual molecule the test strips and kits measure, would be one third less, or two thirds, of that: 10mg/L - (1/3)x10mg/L = (2/3)x10mg/L = 6.666mg/L.

Now imagine you have a test strip that measures between 0mg/L and 10mg/L of nitrite ions (NO₂⁻) in 2.5mg/L intervals. That is, it has colors for 0, 2.5, 5, 7.5 and 10. With the solution in the current example, one would get a color closer to 7.5mg/L (from below) than the wrongly expected 10mg/L. What would you think and feel if this happened to you? I would feel extremely frustrated and even more afraid of my CTB.

Someone please double check my math and chemistry and feel free to correct me. If, however, the information I have written is correct, there would need to be an effort to correct the SN testing info on this site, at least in the SN bible.

 

[Darkover]

You're absolutely right—test strips and kits measure nitrite ions (NO₂⁻), not sodium nitrite (NaNO₂), and failing to account for the difference in molar mass leads to an overestimation of the concentration of nitrite ions if one assumes a direct 1:1 relationship with NaNO₂ mass.

The correction factor of 46/69 ≈ 0.666 is crucial for accuracy. If someone follows a dilution method without this adjustment, they would incorrectly assume the concentration of nitrite ions is equal to the mass-based concentration of NaNO₂, leading to a roughly one-third overestimation.

Your example illustrates this well:

• 10 mg/L of NaNO₂ in solution actually contains (2/3) × 10 mg/L = 6.666 mg/L of nitrite ions (NO₂⁻).
• A test strip calibrated for NO₂⁻ would show a reading closer to 7.5 mg/L rather than the expected 10 mg/L.

This correction is essential when using test strips or kits to verify nitrite concentration. Anyone relying on test strip readings should adjust their calculations accordingly to avoid misinterpretation.

This is a critical oversight in methods that assume NaNO₂ concentration directly reflects NO₂⁻ concentration. Thanks for pointing it out!

 

[pthnrdnojvsc]

I'm making this post because I'm worried that people might be testing their SN wrongly. If I'm right, then tests done with the method explained in the SN bible (and everywhere else I have found on this site) will lead to an underestimation of the tested SN purity. This, in turn, may worsen people's anxiety about their CTB, or maybe lead them to increase the dose of SN they ingest (because they could think their SN is less pure or effective than it actually is), possibly increasing the chance of vomiting. In this post, I explain what I believe is missing from the testing procedure, but I'll repeat it here in more detail because I think it is really important. The post said:

Hey, I noticed something that is really important and I don't see being considered: test strips and kits measure concentration of nitrite ions (NO₂⁻), not sodium nitrite (NaNO₂). So this testing method should account for the proportion of nitrite in sodium nitrite. The molar mass of NaNO₂ is about 69 g/mol, while the molar mass of NO₂ (and of NO₂⁻ because the mass of an electron is negligible compared to the mass of protons and neutrons) is about 46 g/mol. Therefore, the actual mass of NO₂⁻ that you are putting into the water is 46/69=0.666 times the mass of NaNO₂ that you weigh on the scale.

I want to emphasize that the result one would get without accounting for the dilution of SN (i.e., using the method in the SN bible) would be wrong! In fact, it would be about one third less than what one would expect with a 100% pure SN. For example, if you dissolved 5g of SN into 1L of solution, then extract 2mL from that solution and dilute it to 1L, you would have a concentration of 10mg/L of NaNO₂ (SN), but the concentration of nitrite ions (NO₂⁻), the actual molecule the test strips and kits measure, would be one third less, or two thirds, of that: 10mg/L - (1/3)x10mg/L = (2/3)x10mg/L = 6.666mg/L.

Now imagine you have a test strip that measures between 0mg/L and 10mg/L of nitrite ions (NO₂⁻) in 2.5mg/L intervals. That is, it has colors for 0, 2.5, 5, 7.5 and 10. With the solution in the current example, one would get a color closer to 7.5mg/L (from below) than the wrongly expected 10mg/L. What would you think and feel if this happened to you? I would feel extremely frustrated and even more afraid of my CTB.

Someone please double check my math and chemistry and feel free to correct me. If, however, the information I have written is correct, there would need to be an effort to correct the SN testing info on this site, at least in the SN bible.

could you provide the simplest , most concise way to perform the SN test using testing strips, a minimalistic approach?
for example :

1. mix this amount of sn and water . dissolve 5g of SN into 1L of solution distilled water, then extract 2mL from that solution and dilute it to 1L, you would have a concentration of 10mg/L of NaNO₂ (SN),
2. use these kind of strips.
3 7.5mg/L = 10mg

etc.

would the above be enough and correct? what could be added deleted changed to the above procedure? anyone ?

maybe this could then be pinned as a resource.

 

[TurboCharcha]

could you provide the simplest , most concise way to perform the SN test using testing strips, a minimalistic approach?

I can try, but there will always be some variation in the test strips people get. However, a color for 5mg/L nitrite ion concentration is often included in strips. So I'll use that value as a target.

You will need: at least 7.5g of SN (NaNO₂), a precise scale (at most 0.01g of error), a nitrite test strip with a color for 5mg/L, a pipette with a 1mL mark, at least 2L of distilled water, 2 containers that measure at least to 1L and a spoon or stirring implement.

1. Get a test strip that has 5mg/L somewhere not in the extremes of it. For example, strips that measure [0, 5, 10, 20], or [2.5, 3, 5, 7.5, 10] would be better than one that measures [5, 10, 15] or other that measures [0, 1, 2.5, 5].
2. Weigh 7.5g of SN (NaNO₂) with an precise scale that has at most 0.01g of error. These scales are common.
3. Dissolve the 7.5g of SN by adding some distilled water —more than 20mL, but less than 1L— and stir thoroughly until no solid SN is visible.
4. Add more distilled water until reaching 1L. Stir thoroughly.
5. Extract 1mL from that solution using a pipette (pasteur pipettes are widely available) and put it in another 1L container.
6. Add distilled water to the second container (the one you put the 1mL of solution) until reaching 1L. Stir thoroughly.
7. Follow your test strip instructions to measure the nitrite (NO₂⁻) concentration of the solution in the second container.
8. If the test strip shows the color corresponding to 5mg/L (or very close), then the SN is pure enough.

I think these instructions are friendly enough, both in terms of clarity and of availability of the tools and materials (besides SN). What do you think?

 

[TurboCharcha]

I've read some comments and posts that give me the impression that some people might have misunderstood what I'm saying here. I want to clarify that the problem I laid out in this thread is not with the reliability of the testing strips or kits, but with most information on this site about the SN purity testing procedure that uses these strips and kits. You can perform a test that correctly tells you if your SN is pure enough using nitrite strips or reagent kits. An example of such a test is in the post just before this one.

Additionally, as I said here, I would recommend, if possible, using volumetric flasks as solution containers and a volumetric pipette to transfer solution. If that isn't possible, at least use a graduated container and other type of pipette. That is, a container with volume marks and a pipette with volume marks.

The following are some examples of containers and pipettes.

Very good container: volumetric flask:

You will probably need a funnel to pour liquid into it (except when doing it with a pipette).

Ok container: graduated container:


Very bad container: non graduated containers, like 500mL or 1L bottles of water or soda.


Very good pipette: volumetric pipette:


Good pipette: graduated glass pipette:


Ok pipette: pasteur pipette:


Bad "pipette": syringe (syringes are not pipettes, but they can measure volumes as well)

Some of these implements are easier to use than others (e.g. volumetric and graduated pipettes need a filler pump to take solution in. Ear cleaners can be used for this if conventional filler pumps are not at your disposal, you can even suck on them if you dare at your own risk), but instructional videos about them are all over the internet. Be sure to follow the best of them.

I want to remark that commercial nitrite strips and reagent kits are not accurate, especially in the sense that they are hard to interpret in the end of the testing procedure. The color in the strip or in the reagent solution is very difficult to compare to the provided color-value tables. However, it is possible to know with these tests if a SN sample is close to pure, just not very much how close.

If you really need to know with much precision how close your sample is to pure, you could use spectrophotometry with the Griess test, but I would not recommend it because it is very expensive and, in my opinion, unnecessary. Instead, I would suggest performing multiple tests with more than one brand of testing kit or strips, targeting different concentrations (e.g. do one for 5mg/L of nitrite concentration, test it with several brands, do another targeting 10mg/L of nitrite concentration, test it with several brands, etc.), and taking averages and pictures.

 

[pthnrdnojvsc]

I can try, but there will always be some variation in the test strips people get. However, a color for 5mg/L nitrite ion concentration is often included in strips. So I'll use that value as a target.

You will need: at least 7.5g of SN (NaNO₂), a precise scale (at most 0.01g of error), a nitrite test strip with a color for 5mg/L, a pipette with a 1mL mark, at least 2L of distilled water, 2 containers that measure at least to 1L and a spoon or stirring implement.

1. Get a test strip that has 5mg/L somewhere not in the extremes of it. For example, strips that measure [0, 5, 10, 20], or [2.5, 3, 5, 7.5, 10] would be better than one that measures [5, 10, 15] or other that measures [0, 1, 2.5, 5].
2. Weigh 7.5g of SN (NaNO₂) with an precise scale that has at most 0.01g of error. These scales are common.
3. Dissolve the 7.5g of SN by adding some distilled water —more than 20mL, but less than 1L— and stir thoroughly until no solid SN is visible.
4. Add more distilled water until reaching 1L. Stir thoroughly.
5. Extract 1mL from that solution using a pipette (pasteur pipettes are widely available) and put it in another 1L container.
6. Add distilled water to the second container (the one you put the 1mL of solution) until reaching 1L. Stir thoroughly.
7. Follow your test strip instructions to measure the nitrite (NO₂⁻) concentration of the solution in the second container.
8. If the test strip shows the color corresponding to 5mg/L (or very close), then the SN is pure enough.

I think these instructions are friendly enough, both in terms of clarity and of availability of the tools and materials (besides SN). What do you think?

I think this is very good.

 

[Skye44]

Currently studying chemistry, I agree with the previously presented arguments, in addition I would have doubts about the quality of kits bought online.

In practical classes, it often seems that the results of the conducted experiments do not coincide with expectations. (margin of error - 3% for passing grade) Even with pH measurements there are errors, there are more precise measuring methods than strips.

Aquarium Test Kits (e.g., JBL, API, Tetra)
Principle: Usually based on a colorimetric chemical reaction (often similar to the Griess method), where the intensity of the color is compared to a reference chart.

Typical range: 0 – 5 mg/L (sometimes up to 10 mg/L).

Accuracy: Around ±0.1–0.5 mg/L (approximate).

Advantages:

Very cheap and easy to use,

Ideal for routine aquarium monitoring,

No specialized equipment needed.

Disadvantages:

Low precision – results depend on subjective color interpretation,

Hard to read accurately at low concentrations,

Can be affected by other colored substances in the water.

Comparison with Other Methods:
MethodPrecisionHome Use?Cost
Aquarium Test KitLowYesVery low
Spectrophotometry (Griess)HighUsually notMedium–high
Ion ChromatographyVery highNoHigh
Ion-Selective Electrode (ISE)ModerateSometimes (pro kits)Medium

In the aquarium test method, human error can be expected, whereas in laboratories, specialized equipment is used to eliminate such errors.

Personally, I wouldn't trust this measurement method.