View Full Version : salinity calibration fluid confusion

05/02/2011, 09:56 PM
how does it work??

just kidding

One would, or better put I would assume that if a bottle of pinpoint was sitting around for a while, and it evaporated some due to age, that it would result in calibrating your refractometer high. Meaning that if you followed its results your actual system salinity would end up on the high side of your intended target...not the low side.

That said, I have had the opposite effect with a bottle that was a couple of years old, and cant help but wonder how, and if the stuff being old on its own could possibly sway the results the other way, and the inaccuracy maybe had nothing to do with evaporation at all, but some other reaction due to age.

Either that, or the brand new bottle I recieved is off two full points, or the original bottle has been off all along.

If anyone followed that rambling..........thoughts?? :)

05/02/2011, 10:22 PM
Well when you find out the answer i wanna know

05/02/2011, 10:22 PM

If it does go bad per say, would say calibrating it with the new solution and then calibrating with distilled water. Then knowing how far off it is with distilled and adjusting it accordingly, that way you wouldn't have to worry about the solution going bad....

I don't know if I make sense lol

05/02/2011, 10:27 PM
distilled isnt going to help figure anything out

I could go to the effort of following Randys method to make my own calibration fluid, and probably will anyway to get another view. But I have always counted on pinpoint being accurate, and simply dont know what to believe at this point.

If they can simply go bad and end up with a result in the direction I described, then it will help my confidence in my new fluid. Or if I am simply somehow misunderstanding the result evaporation could have, that could solve my doubts as well.

05/02/2011, 10:27 PM
I think the distilled water can fluctuate a little bit, but also don't you have to calibrate em every year so it shouldn't be too bad buying new solution kind of a pain in the butt though... someone get all chem status in here

05/02/2011, 11:02 PM
If the calibration fluid went high, then the refrac is calibrated high. So when you measure a known solution that is right, it reads low. Say the fluid is supposed to be 1.026 but was actually 1.030. So now the 1.026 mark on the refractometer really means 1.030 because you set it there with the bad solution. Now a solution that truly is 1.026 reads 1.022 or something.

If it went the other way, then that is curious.

05/03/2011, 12:03 AM
If it went the other way, then that is curious.


hence my position of doubting everything at this point

new solution read 1.028 to two different refractometers calibrated to the old solution......which IF accurate puts my systems all at 1.024, and furthermore means I have been maintaining parameters unbalanced to salinity in all of my systems for who knows how long

Randy Holmes-Farley
05/03/2011, 04:48 AM
I agree the tank water will read low if some of the standard evaporated. If it is very (very) humid around it, water can condense into it and have the opposite effect. Accidently getting fresh water into it will also have that effect, of course.

Someone may have bought it, used some, refilled with fresh water, and returned it to the store as well.

05/03/2011, 07:14 AM
Thanks Randy :)

quote: "I agree the tank water will read low if some of the standard evaporated"??

did you say what you meant there, as that isnt what I or disc said??

If the standard evaporated, the salinity of the calibration solution would raise, and if you referenced this so would your tank water. Or is that not accurate somehow??

It definitely wasnt compromised with water(unless I drooled and didnt realize it)

Although, just how humid would it have to be to condense water through a closed lid??

I cant imagine that could be it although my fishroom has been 85 for periods of time, before I got a handle on it

this is bugging me :)

Im going to order some new fluid today and see what it says

05/03/2011, 08:14 AM
Could something have precipitated from the solution and lowered its concentration. That doesn't sound likely, but would explain the results.

05/03/2011, 08:16 AM
heres a question:

Has anybody ever experienced, or even heard of a brand new Pinpoint salinity calibration fluid that was off??

05/03/2011, 08:17 AM
My pinpoint fluid settles if let to sit around for a couple of months. Try shaking it up for a minute or so. I noticed this when I had a large water change using NSW and the salinity came up way low from normal. After shaking the calibration fluid and rechecking the instrument it was normal.

Randy Holmes-Farley
05/03/2011, 10:25 AM
It settles? Something may be wrong then. A fully dissolved salt solution shouldn't settle. Maybe it was just mismeasurement the first time. :D

Randy Holmes-Farley
05/03/2011, 10:25 AM
Has anybody ever experienced, or even heard of a brand new Pinpoint salinity calibration fluid that was off??

I seem to recall such threads, but whether it was real or measurement errors, I do not recall.

05/20/2011, 12:51 PM
heres a question:

Has anybody ever experienced, or even heard of a brand new Pinpoint salinity calibration fluid that was off??

Yes I have!

I bought two bottles of pinpoint solution about a year ago and gave one to a buddy. We showed our salinity was too low in our display tanks so started adding salt directly to the sump to correct the issue. Both of us have experienced coral loss and I've lost quite a few fish over the last 6-8 months. This past week I ordered a different solution and low and behold it showed that my salinity was way too high (1.031)! Do not use Pinpoint calibration fluid for your refractomer. Not sure how it works with probes.

Randy Holmes-Farley
05/20/2011, 05:35 PM
How did you determine which fluid was off?

05/20/2011, 05:57 PM
Good question. I checked the salinity of my tank vs four other tanks and they all were all 5ppt lower than mine. I also checked ro water against both fluids. With the pinpoint fluid ro water was well below the base line on the refractometer. With the new fluid ro water showed zero. But above all my sps were doing poorly and I had lost a few new frags and other colonies that had been with me for a while.

05/20/2011, 06:14 PM
heres a question:

Has anybody ever experienced, or even heard of a brand new Pinpoint salinity calibration fluid that was off??

This happened to me years ago. A lab made NaCl reference corrected the issue. Later, helping my kid make Randy's DIY reference sol'n for science fair also confirmed this, and that it is feasable to DIY.

I had guessed the reefing hobby reference I purchased was either faulty or tampered with, it was too dilute. :)

Randy Holmes-Farley
05/21/2011, 05:21 AM
Could be quality control problems with the Pinpoint, or maybe someone used some, replaced it with water, and returned it. In principle it should work fine.

05/21/2011, 09:15 AM
I dont see it as very likely at all that anyone would take a few samples out and replace weiht fresh...but you never know

regardless.......I have since made my own(with a marginal scale) and purchased 3 additional new ones. 2 pinpoints and a milwaukee.

If, for conversation purposes, we call my original bottle(and tank water for who knows how long) 1.026, the other solutions were reading as follows:

original new pinpoint that made me start this thread: 1.028
new pinpoint #2- 1.0275ish
New pinpoint #3-1.027
new milwaukie -1.027
DIY- 1.027

still very odd to me that my original old one went that direction(unless it was from the beginning which now seems likely), but while I still dont have complete 100% confidence in the exact final number I am obviously just going to call the 3 examples that read 1.027 good enough.

3 different new pinpoints all reading differently, which answers my question as to has anyone ever gotten a pinpoint that is off. Yes I have, at least two of them, out the last three I have bought in the last month

05/21/2011, 02:53 PM
Some of our livestock comes from the Red Sea

The Red Sea is one of the most saline bodies of water in the world, due to high evaporation. Salinity (http://en.wikipedia.org/wiki/Salinity) ranges from between ~36 in the southern part due to the effect of the Gulf of Aden (http://en.wikipedia.org/wiki/Gulf_of_Aden) water and reaches 41 in the northern part, due mainly to the Gulf of Suez (http://en.wikipedia.org/wiki/Gulf_of_Suez) water and the high evaporation. The average salinity is 40 . (Average salinity for the world's seawater (http://en.wikipedia.org/wiki/Seawater) is ~35 on the Practical Salinity Scale, or PPS; that translates to 3.5 % actual dissolved salts.)

So I don't think 0.0005 is going to kill anything