Pinpoint solution

[cham]

Does it ever go bad??

I have one of the regular blue refracto's and calibrated it 4 years ago or so with the pinpoint solution. I used to check it every few months for years but it was always dead on and I figured there was no reason to keep checking it.

Well it has been a couple years and so I decided to check it. The solution is reading 1.030 when it should be 1.026 so now I don't know if its the solution that's off or the refractometer.

Solution was stored inside the house in a dark cabinet with the lid on tight.

 

[coralsnaked]

Hummm ?
I would think if anything the solution would test higher due to evaporation, but in relaity should not change with the cap on tightly.

These bottles are so small and i use mine up as I retest my meters weekly. I do have to make small adjustments from time to time as the house changes temps with the seasons.

National instruments has it for a couple of bucks mailed to your front door in a couple of days.

Merry Skerry

 

[disc1]

It doesn't go bad on it's own, but two things can happen to it. If it isn't tightly sealed then the water can evaporate and the salinity in it goes up.

If it gets too hot or cold, then precipitation can happen that will drive the salinity down.

Kept tightly sealed and away form temperature extremes it should last for a good while. I think if it were several years old I would want to replace it. Especially if it suddenly gave a reading I wasn't expecting.

 

[cham]

Thanks guys, I went ahead and ordered a new one with two seperate calibration solutions so I'll have two seperate opinions in the future.

My old one was getting corroded anyway

 

[disc1]

My old one was getting corroded anyway

Oh yeah, and salt creep... That will definitely change it to a lower value.

 

[cham]

No I meant my old refractometer was corroded. The metal around the prism is bumpy and rusty.

 

[cham]

So I get my refractometer from BRS today and it comes with a 53mS 35ppt calibration solution from Aqua Craft Products with the refractometer. This is what I bought:

http://www.bulkreefsupply.com/refractometer-for-reading-salinity-with-calibration-fluid.html

I also bought a new bottle of Pinpoint 53.0 solution so I'd have something to double check it with.


Well out of the box the aqua craft solution reads dead on 35ppt. But the new bottle of Pinpoint reads 38ppt. So here I am $60 later with the same issue I had before :mad2:


Which one is right????

 

[Whitebeam]

Sounds like you have bought a refractometer calibrated for saltwater rather than one calibrated for seawater. Based on my own tests and work with various calibration solutions I'd believe the new bottle of Pinpoint solution.

All of that said - if you calibrate a saltwater refracto to 35ppt using a reference solution with the same refractive index as S=35 salt water (which I believe the Pinpoint solution is), your refracto will now be properly calibrated.

There are any number of threads on here discussing the differences between salt water and seawater refractos. Possibly worth doing a search and spending a few minutes reading about the issues and the very limited numbers of true seawater refractos out there.

HTH

Peter

 

[cham]

Sounds like you have bought a refractometer calibrated for saltwater rather than one calibrated for seawater. Based on my own tests and work with various calibration solutions I'd believe the new bottle of Pinpoint solution.

All of that said - if you calibrate a saltwater refracto to 35ppt using a reference solution with the same refractive index as S=35 salt water (which I believe the Pinpoint solution is), your refracto will now be properly calibrated.

There are any number of threads on here discussing the differences between salt water and seawater refractos. Possibly worth doing a search and spending a few minutes reading about the issues and the very limited numbers of true seawater refractos out there.

HTH

Peter

Hi Peter, thanks for the info.

I'm pretty sure the refracto that bulk reef supply sells is made for sea water since it's a reef store but I could be wrong on that.

 

[bertoni]

I'm not sure which solution is correct. You could try the DIY formula as a sanity check:

http://reefkeeping.com/issues/2004-06/rhf/index.htm

 

[Whitebeam]

Or buy some FM Multi-Reference for a casting vote - available from Cherry Corals if you're in the US. Yet more $$ though.

I now make up Randy's home-made reference solution as per Jonathan's post and validate each batch by comparing it to the FM and/or Pinpoint reference - once I've proved that all three read near-enough the same I'm set for a while and it works out reasonably economical that way 'cos I only use a small amount of expensive commercial reference every now and then.

Peter

 

[masonicman]

I just order my new PINPOINT® Salinity Calibration Fluid from American Marine because my pinpoint meter was reading the solution at 5.6 when I was calibrating it. I knew my meter was not off that much, so I called AM and asked the tech does the solution ever go bad and he told me that the water in the solution will eventually evaporate causing an increase in salinity reading.