DIY Salinity calibration solutions

[JimWelsh]

Jim, I feel like you need a hug.

LOL. Thanks. I've been in a mood lately. Not sure why.

Can you link me to something you'd consider to be a reasonably priced 1L VF?

First hit when I just googled "1000 ml class a volumetric flask".

Plugging that same search phrase into Amazon's search, you will find many similar, with prices down to even around $12-13. The first one I got a few years ago was around $18.00, and was within spec (which I know because I *ahem* calibrated it).

 

[purp]

I bought one Jim. Your crusade has had an effect. Positive or negative no one knows, but Jeff Bezos is now a little bit richer.

 

[reefwiser]

What wrong with a volumetric glassware. The average hobbyist needs all they help they can get when preforming this task. Using the right tools when doing DIY makes all the difference.

 

[Randy Holmes-Farley]

What wrong with a volumetric glassware. The average hobbyist needs all they help they can get when preforming this task. Using the right tools when doing DIY makes all the difference.

Nothing is "wrong" with it. It is certainly more than adequate for DIY salinity standards. Nothing is wrong with typewriters, either.

In my lab, we choose to use 21st century methods like balances for measuring liquids too large in volume for a pipette. lol

 

[reefwiser]

I think that in this case we need to teach hobbyist’s the various tools. Making fun for lab tools should not be done. Teaching lab practices is important. Teaching is not a LOL function.

 

[purp]

k

 

[Randy Holmes-Farley]

Teaching is not a LOL function.

Hmm. Maybe you were my third grade teacher. No lol there.

 

[Rybren]

Hmm. Maybe you were my third grade teacher. No lol there.

Same for me. Unfortunately, my 3rd grade teacher was also my sister, so there was no escape.

 

[bozo]

I have pure KCL in my lab.

We use it to make a reagent for washing our fluorescent probes off FFPE.

@Randy Holmes-Farley Do I need to bake it prior to mixing?

Also I don't understand the issue with the measuring of water. I breezed through the posts about exact measurements etc.

If youre already weighing your NaCl, just tare your cup and measure your water.

Forget the graduated cylinder.

1 mL H20 = 1 gm H20

 

[purp]

The reagent grade KCl i've used in the past was very clumpy. If you do measurement by mass and it has aborbed water, you won't get an accurate weight. I baked mine.


Just because a measurement is easy does not mean it's precise or accurate. I am striving for the best accuracy and precision can reasonably (and economically) obtain. My scale was off by a few grams when compared with a volumetric flask for RODI measurements. Granted, this was not a lab grade scale, but lab grade glass ware is substantially cheaper than a lab grade scale.

 

[Randy Holmes-Farley]

I have pure KCL in my lab.

We use it to make a reagent for washing our fluorescent probes off FFPE.

@Randy Holmes-Farley Do I need to bake it prior to mixing?


1 mL H20 = 1 gm H20

That’s not perfect, and is an unnecessary conversion as ppm is mg/kg.

i’d dry the KCl just in case it has absorbed significant moisture.

i do agree that mass is a good way if the scale is reliable.

 

[xtian]

I’ve always purchased solution but want to try this. Is a digital scale okay for it? How long is the solution good for? @Randy Holmes-Farley

 

[Randy Holmes-Farley]

I’ve always purchased solution but want to try this. Is a digital scale okay for it? How long is the solution good for? @Randy Holmes-Farley

A digital scale is good if the accuracy and precision are suitable.

To know for sure it is suitable, one can get cheap calibration weights from Amazon to verify the scale accuracy.

 

[Aclman88]

Bumping this old thread, but does a salt containing sodium silicoaluminate work? I notice this is insoluble in water, so my guess is it would alter the calibration negatively.

 

[Aclman88]

Bumping this old thread, but does a salt containing sodium silicoaluminate work? I notice this is insoluble in water, so my guess is it would alter the calibration negatively.

 

[Randy Holmes-Farley]

Bumping this old thread, but does a salt containing sodium silicoaluminate work? I notice this is insoluble in water, so my guess is it would alter the calibration negatively.

Ideally, best without, but the amounts of quite small and we do not require accuracy better than our devices are capable to detecting.

 

[Aclman88]

Ideally, best without, but the amounts of quite small and we do not require accuracy better than our devices are capable to detecting.

Thanks for the quick reply. I wasn't sure, I may just use it now and try with some other salt later and compare... the stuff with silicoaluminate is the only kind I have in my classroom.

 

[DeputyDog95]

Don't use a salt mix. Use table salt (iodized or not doesn't matter).

The recipes are different for refractometers, conductivity devices, and hydrometers.

Weighing is better than volume measurement of the salt, if you can do it.

For a refractometer:

Use 3.65 weight percent sodium chloride solution to match 35 ppt (sg = 1.0264). It can be made by dissolving 3.65 grams of sodium chloride in 96.35 grams (mL) of purified freshwater.

For a rougher measurement in the absence of an accurate water volume or weight measurement:

1. Measure ¼ cup of Morton's Iodized Salt (about 73.1 g)
2. Add 1 teaspoon of salt (making about 79.3 g total salt)
3. Measure the full volume of a plastic 2-L Coke or Diet Coke bottle filled with purified freshwater (about 2104.4 g)
4. Dissolve the total salt (79.3 g) in the total water volume (2104 g) to make an approximately 3.65 weight percent solution of NaCl. The volume of this solution will be slightly larger than the Coke bottle, so dissolve it in another container.

If you have a 100 mL graduated cylinder, use exactly 3.65 grams of salt and 96.35 mL of fresh water. It is tricky to volume measure such a small amount of salt, but that is about 0.59 teaspoons of Mortons.

So my little scale only goes up to around 100 grams (less the weight of the liquid container). Could I half the recipe for the refractometer solution and use 1.8 grams of Iodized salt and 48.2 grams of distilled or RODI water and get the same result?

Conversely, if I get a bigger scale, can I double it to make more solution?

I would assume both would be true, but you never know...

 

[nereefpat]

Could I half the recipe for the refractometer solution and use 1.8 grams of Iodized salt and 48.2 grams of distilled or RODI water

The error is going to be a pretty big % with that small of a measurement.

I would weigh 36.5 grams of table salt and add it to 963.5 grams of water. Easily done in a canning jar.

 

[DeputyDog95]

The error is going to be a pretty big % with that small of a measurement.

I would weigh 36.5 grams of table salt and add it to 963.5 grams of water. Easily done in a canning jar.

Ok, thanks. I'll need a bigger scale I guess. The small digital scale I'm using was throwing errors when I tared it with the plastic mason hard and added the 963.5g of water. It's only good for 100g total. So the water plus the plastic jar must have been exceeding the limit.