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 be detected by the test kit.
When we get a result in the middle of the range we can feel more confident in what we're seeing.
We can also detect test method errors if we see results significantly higher than the middle, since that shouldn't be possible in a valid test.
Basic idea :
Deliberately create an SN solution whose concentration is in the middle of the test kit range, provided the SN is 100% purity, by dissolving a known amount of SN in a known volume of water.
e.g. If our kit tests up to 10mg/L, then create an SN solution of 5mg/L (assuming 100% SN purity), by placing 5mg of SN into 1 litre of water. If the kit shows around 5mg/L, then the SN must be almost 100% pure.
The numbers used below assume a kit that tests up to 10mg/L.
Modify the numbers based on the range of your test kit.
Equipment :
Kitchen scales that can measure to 0.1g accuracy (or better) for method 1, or to 1g accuracy for method 2
Aquarium test kit that tests up to 10mg/L nitrite.
Two 1 litre bottles of water ("bottles 1 and 2"). Ideally use distilled water, though I assume you could probably use regular mineral water, or maybe even tap water.
Syringe or pipette that can measure 5ml for method 1, or 0.5ml or 1.0ml for method 2
(though if you have a 1ml syringe or pipette then you could use it 5 times when the step requires 5ml to be extracted)
(note : If you don't use distilled water then you may want to separately test some water from the same source, without any SN added, to check the "baseline" level. You should see close to the minimum on the test range. You could still do this if using distilled water, to validate the test kit gives sensible results).
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Method 1 : Requires kitchen scales with 0.1g accuracy (or better)
Weigh out 1.0g of SN and dissolve it in bottle 1.
Put lid back on, shake *very* well.
Bottle 1 now contains 1.0g/L of SN
Use syringe to extract 5ml of liquid from bottle 2.
Squirt liquid away to discard it.
Syringe should now be empty.
Use syringe to extract 5ml of liquid from bottle 1.
The extracted liquid contains 5mg of SN.
Squirt extracted liquid into bottle 2.
Put lid back on, shake bottle 2 *very* well.
Bottle 2 now contains 5mg/L of SN.
Test liquid from bottle 2 using test kit.
If tests show around 5mg/L then the SN was close to 100% purity.
If tests show significantly higher than 5mg/L then the test has been wrongly performed or the test kit is faulty.
If tests show significantly less than 5mg/L then it suggests the SN is of lower purity and may be unsuitable.
Disposal : After testing, further dilute liquids while discarding, e.g. slowly pour liquid into stream of water from tap or from another bottle of water.
This applies particularly to bottle 1 (more concentrated).
After completing the test successfully, you may wish to do another which targets the upper end (maximum) of the test kit to measure the percentage purity of the SN more accurately (if you feel the need). If the values you used for the first test exactly targeted the middle of the test range, then you can simply double the ml amount that is transferred from bottle 1 to bottle 2, eg modify above steps, replacing 5ml (both instances) with 10ml (or you could double the SN amount in g, but that wastes SN for no real benefit).
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Method 2 : If your kitchen scales can only measure to 1g accuracy
This requires a syringe that can measure 0.5ml fairly accurately. If your syringe can measure 1ml accurately, but not 0.5ml, then modify steps, replacing 10g with 5g, and replacing 0.5ml (both instances) with 1ml, although this will be less accurate.
*Be careful* due to higher SN amounts. Ensure disposal steps (see above) followed.
Weigh out 10g of SN and dissolve it in bottle 1.
Put lid back on, shake *very* well.
Bottle 1 now contains 10g/L of SN
Use syringe to extract 0.5ml of liquid from bottle 2.
Squirt liquid away to discard it.
Syringe should now be empty.
Use syringe to extract 0.5ml of liquid from bottle 1.
The extracted liquid contains 5mg of SN.
For remaining steps, see method 1 (squirt extracted liquid into bottle 2, etc).
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ANOTHER EXAMPLE :
Test kit that measures 0.3 to 3.3 mg/L
We will aim to create a solution of 2 mg/L.
Method 1 : Requires kitchen scales with 0.1g accuracy (or better)
Weigh out 1.0g of SN and dissolve it in bottle 1.
Put lid back on, shake *very* well.
Bottle 1 now contains 1.0g/L of SN
Use syringe to extract 2ml of liquid from bottle 2.
Squirt liquid away to discard it.
Syringe should now be empty.
Use syringe to extract 2ml of liquid from bottle 1.
The extracted liquid contains 2mg of SN.
Squirt extracted liquid into bottle 2.
Put lid back on, shake bottle 2 *very* well.
Bottle 2 now contains 2mg/L of SN.
Test liquid from bottle 2 using test kit.
If tests show around 2mg/L then the SN was close to 100% purity.
If tests show significantly higher than 2mg/L then the test has been wrongly performed or the test kit is faulty.
If tests show significantly less than 2mg/L then it suggests the SN is of lower purity and may be unsuitable.
Follow disposal steps (see above)
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Method 2 : If your kitchen scales can only measure to 1g accuracy
This assumes a syringe that can measure 0.5ml fairly accurately. If your syringe can measure 0.25ml accurately, then modify steps, replacing 4g with 8g, and replacing 0.5ml (both instances) with 0.25ml, for better accuracy.
Weigh out 4g of SN and dissolve it in bottle 1.
Put lid back on, shake *very* well.
Bottle 1 now contains 4g/L of SN
Use syringe to extract 0.5ml of liquid from bottle 2.
Squirt liquid away to discard it.
Syringe should now be empty.
Use syringe to extract 0.5ml of liquid from bottle 1.
The extracted liquid contains 2mg of SN.
For remaining steps, see method 1 (squirt extracted liquid into bottle 2, etc).
other useful threads :
https://sanctioned-suicide.net/thre...he-aquarium-testing-strips.31522/#post-589366
https://sanctioned-suicide.net/thre...-an-aquarium-testing-kit-rough-version.18188/
( haha)
