New Salinity Stds

[Boomer]

Randy and I have been working on some new salinity stds. Based on the data I found for him he has come up with new numbers. The old numbers were to low. ie, the new 3.65 use to be 3.6 and the 3.17, is now 3.28 and the 3.714 was 3.7


Salinity Standards

Here's a compilation of salinity standards that people can make out of dry table salt and water (using a good balance):

If you want an S=35 standard for specific gravity, try 3.714 weight percent NaCl in water at 20 deg C

If you want an S=35 standard for refractive index, try 3.65 weight percent NaCl in water

If you want an S=35 standard for conductivity, try 3.28 weight percent NaCl in water

Some will ask what is a weight % ;



So.....


3.28 % = 96.7 ml of water and 3.28 grams of NaCl
Or add 80 ml of water to a graduated container, then add 3.28 g of NaCl. Once dissolved then add water to the 100 ml mark. Or if you will, 96.7 g of water and 3.28 g of NaCl

[Witfull]

Mr. Wizard is in da house....keep up the great work boomer!

[NaH2O]

Boomer, can you explain why it is good to know a salinity standard? I followed what the weight percent is....and in fact I have a graduated cylinder at home, but not a good balance (and I don't have good balance either)

Another question, why was the new standard for conductivity a larger change (from the old standard) in comparison to the standard changes in specific gravity and refractive index. (i.e 3.17 ---> 3.28, compared to 3.6 ---> 3.65 and 3.7 ---> 3.714)

[Boomer]

can you explain why it is good to know a salinity standard?

Because it puts a stop on all the arguing of what salinity tester is good or bad and tells you where your reef tank really is. As I brought up before many are using refracts and this solution will let you calibrated the refract so it is as if it is measuring the refractive index of seawater. Your refracts are , say, calibrated with a 3.5 % solution of NaCl, which means right out of the box it is not reading right for seawater. So when someone says it reads, 3.5 %, 35 ppt or 1.026, "it is perfect" it is actually reading to low. I have said when using refracts just up it 1 unit, so it reads 1.027, which = about 1.026 NSW. The is just a rounded of value, not exact and the calibration solution will put you right on the noise. Know one can argue with you Now go make comparisons to SG meters, to see where they are at. People ASSUME because it is a refract it must be right on, not so. You can do the same with a SG meter or a conductivity meter. You can always go to the local drug store and get them to do it So now, if everyone did this, we would know where the h--- we are at when talking "what is your salinity"

why was the new standard for conductivity a larger change

Conduct is a much more complicated issue and Randy didn't have enough good data, in order to calculate it. Here is some light reading for you, I'm sure you will see what I mean.



http://www.wileywater.com/Contributor/Sample_2.htm

http://global.horiba.com/story_e/con...ctivity_02.htm

[NaH2O]

OHM my! I'll take my time and read through those links...Thanks, Boomer.

Wow! Thanks for the helpful information. The point difference on the refracts is frustrating. If hobbyists don't realize it, then (as you said) their salinity is too low - and not the value they are trying to obtain.

Hmmm....I wonder where I can get my hands on a good balance.....

[ScottT1980]

Nikki, check out ebay, you can find some decent ones for about 20 bucks. You can also go to gun stores and get balances that measure things in grains. You can then convert grain to grams:

1 grain = 0.06479891 gram

Take er easy
Scott T.

Edit: I say decent, I wouldn't trust them with my research but I would certainly use them for applications with the aquarium...

[Boomer]

Nikki

Short note.

99.99 % of all refractrs, we would use in the hobby, are calibrated to NaCl Salinity. Salinity does not mean seawater salinity, it could be KCl, NaCl Salinity etc.. It is the salinity of any "salt". Seawater Salinity is not the same as NaCl Salinity or KCl Salinity, each has its own RI (Refractive Index). In other words, a 35 ppt NaCl RI is not the same as a 35 ppt RI for KCl or Seawater. In order to calibrate a refract to NSW you would want a sample that had the same RI as seawater. So, that would be a sample of seawater that is know to be 35 ppt or to mathamatically calculate a salinity using another salt that would = NSW. Such is the case with the 3.65 % NaCl, which = NSW @ 3.5 % Salinity.

[EdgeKrusher]

Thanks Boomer. Now it's finding a scale.

[birdman204]

Originally posted by Boomer
......... in water at 20 deg C ...........

This is one part of the equation only brought up once, and probably has a LARGE factor into actual readings.
Temperature has a LOT to do with the rates of solution for these substances. A CONSISTENT temperature will ensure consistent mixes, if your temps are off.... Your final Values are off.. Just wanted to emphasize this.
Sounds like you're a Chem dude, and I am sure you are aware of the role temperature plays in this study. I understand that sometimes those who have "been there done that" tend to forget the importance of little things that are often overlooked by newbies simply because we take some of this knowledge for granted.
I.E. a SW aquarium runs at 8.2 PH and may go down at night... We may tell someone to drip kalk at night but that person doesn't realize exactly why
Lets make CHEM popular again!

[NaH2O]

Boomer,

I have a question about the grade of salt required to conduct this calibration....

In my cabinet, I have Iodized Sea Salt. Would I need to have uniodized salt in order to get an accurate result? Ingredients: salt, calcium silicate (anitcaking agent), dextrose, potassium iodide, sodium bicarbonate. Do we need to take into account the other ingredients....do we need analytical grade salts to do this?

[Boomer]

This is one part of the equation only brought up once

Thats for a hydrometer. Refracts and conductivity meters are automatically compensated for, just as a pH meter is for temp. However, it is still a could idea to do it at 20 C, if you are comparing. I 'm going to have to get that 20C changed to 25 C, which is what many of the LFS hydromters are calibrated to.

[birdman204]

Sure. I am not referring to the salinity reading temps though, I am talking about water used for mixing temps.
I am meaning to relay the ability of certain compounds to dissolve in water of different temperatures.... The same amount of salt in different temp. waters will give 2 different salinity readings.
Like when you take water and add sugar, you get sweet water. But if you boil it, you can add more sugar as it wouldn't dissolve at the lower temps, then you take it off the heat, and you get syrup when it cools because the water, when cooled, cannot maintain the physical properties it could when it was hot ( in this case, holding the escess sugar ). Hope that analogy helps some others understand.

[Scooterman]

This is a good one for the books, thanks Boomer.

[Boomer]

Nikki

Randy ran some test on Iodized Sea Salt, the dif is so nil it make no dif.

Bird


The same amount of salt in different temp. waters will give 2 different salinity readings.

No, on a refract or conductivity meter, they will be the same.

Salinity is salinity it is not affect by temp. 35 ppt =35 ppt no mater what the temp is. What is affected by temp is Specific Gravity and hydrometers measure SG. A refract or conductivity meter that does not have ATC (Automatic Temp Comp) will be affected by temp. However, I know of no one in this hobby that uses one without ATC for seawater mixing. So we are really only left with the hydrometer. However, some hydrometers, i.e SeaTest use thermal expansion plastic, so they too are ATC in a sense.

Lets expand on this, so no one is lost

If you want an S=35 standard for specific gravity, try 3.714 weight percent NaCl in water at 20 deg C

This means that at that temp and solution std the Salinity is = 35 ppt NSW. Now what does the hydrometer read ? That will be the number to use on the hydrometer when mixing at 20 C. If one wants, then raise the temp up to any temp you want and look at that number on the hydrometer and that number will = 35 ppt NSW




Like when you take water and add sugar, you get sweet water. But if you boil it, you can add more sugar as it wouldn't dissolve at the lower temp

That is a whole different issue and you are confusing people with this

You are talking about saturation, as in 100 % and we are at 3.5 %, we will say, no where near saturation. If you dissolve 3.5 grams of NaCl in water at 20 C there will be the same exact amount at 30 C or 15 C, as long as there is no evaporation or precip. And there won't be at these temp. Second, not ALL substances dissolve more/hold more in solution at warmer temp. For example, you can get more Ca(OH)2, aka Kalk, in solution at 20 C than yon can at 25 C. Lastly, there is the tricky thing called activity. The more of salt x you have in solution the more of salt y and z you can dissolve in solution, i.e. If you took a glass of FW water and dissolved NaCl to 100 % saturation and measured the amount and then took a glass of seawater and dissolved NaCl in it to saturation and then measured the total NaCl in both, the seawater glass would have more NaCl than the FW glass. This is why seawater can dissolve more CaCO3 than FW.

Activity is the wanting of a substance to go some place and do something. If it has a low activity it doesn't want to go anywhere, so it stays/likes to be in solution. Something with a high activity is not happay in solution, it wants to go some place and do some thing, so the only thing it can do is precip out of solution, to make itself be happy.

Here's another try at explaining activity

If you think of Mg(OH)2 dissolving, you are going from a solid where the Mg++ and OH- are very near to each other,
to dissolve into Mg++ and OH- that are farther apart. So there is an electrostatic energy of interaction between
the positive and negative charges that is lost when those ions are pulled apart.

In very dilute solution, that effect is countered by the energy that is given off when water surrounds each ion that
comes off. That is why salts dissolve at all.

So in the end, you reach a balance between the lost electrostatic energy, and the gained hydration energy (ignoring
things like entropy for the moment).

OK, so now look at the situation with a large amount of Na+ and Cl- ions also in solution.

In that case, the Mg++ and OH- ions that go out into solution are not so all alone. An Mg++ can have nearby Cl- ions,
and the OH- can have nearby Na+ ions (providing some electrostatic energy). So the electrostatic energy lost is not so
large. Since the hydration energy stays largely the same, the overall solubility goes up.

So most ionic salts are more soluble in NaCl solutions than in water. And most acids and bases that tend to ionize will
be more prone to be in their most highly charged form. This is one reason why pKa's sometimes shift considerably between
freshwater and seawater.

[birdman204]

You are correct, but the sugar issue may be a "whole different issue", but it still demonstrates a point.
For you to say that this doesn't matter.... temp doesn't matter on what rate an inorganic solid dissolves into a liquid, is not 100% correct. Yes your salt may be mixing at the right rate, but what about everything else in your mix? Are the chemical reactions that are needed to create all the ionic compounds gonna happen in say, 50 * water? what about 85* water. Temp also affects many other things in the water besides salinity. I just wanted to stress that this is an important factor
BTW, if you know of no-one in this hobby that uses the Deep - six, or a float meter, you must not know very many people in this hobby. THAT is the reason I wanted to add this info, believe it or not, there are some who are not buying a 50$ + refractometer, I just figured the information was pertinent.
As an intelligent person, I would assume you are aware that our refractometers are laughable in compairison to what would truly be needed to get accurate readings for an study such as this.... Extremley accurate Lab grade refractometers are far too bulky and pricey for the average aquarist to keep on hand. Are you using this type of equipment or a hand held refractometer? I use a hand held myself.