Refractometer @ swingarm SG testers

That refract is the same one I posted. You can find it on the site I gave in China, Huake Instrument Co.

How can they say it is for SG when it is really not?

Because they make a conversion factor for RI (Refractive Index) to SG. It is quite common, all refracts do this for any thing they are measuring. They can do the same for Salinity, sugar solutions, blood, battery acid, engine coolant, beer etc.

Now for the big hammer. : We have been TRYING to get reefers to use SALINITY and not SG. Most reefers know the NSW is 35 ppt, but they are all over the board with SG, as they do not understand it AND there are many misleading things about SG. Salinity is short and simple, be at 35 ppt always. And yes the refract need to read 36 and not 35, the error is till there. One reason is that if you raise temp or lower the temp of NSW the Salinity does not change !!!!!! but the density or SG does !!!!!. However, there is no device that really measures NSW in PPT, accept for a EC meter and not really there either or a refract set to NSW ,the same also. Salinity is really measured, in short, by taking 1 kg and removing all the water and then measuring the dry weight of what it left. All other measurements are more or less correlated conversions. They all work well if you understand them. SG is really simple but it really confuses people, because of the temp thing and all the dif calibration temps you can get them at. It would be easy that if from day one there was only one temp for an SG hydrometer. But nope, some knot heads had to have them at dif temp for there need, yet all, convert back to the same thing, if you have a table .An SG hydrometer should only be calibrated to 4 C PERIOD, the maximum density of water. There would not be all this confusion if this was so

 

Boomer,
For all us brain dead people let me just say that NaCI is Sodium Chloride, basically table salt.


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 3.7 weight percent NaCl in water at 20 deg C

If you want an S=35 standard for refractive index, try 3.6 weight percent NaCl in water

If you want an S=35 standard for conductivity, try 3.17 weight percent NaCl in water

OK for those of us that don't have a scale or a way to measure this what would you suggest we do? I am wanting to get my refractometer right on the money. I take it that I should be using the 3.6 weight, and how much water should be used when mixing these.

Thanks for being so informative here we all thank you
[smiley=argue.gif] [smiley=book2.gif] [smiley=gossip.gif] [smiley=huh2.gif] [smiley=idea.gif] [smiley=help.gif]

 

I take it that I should be using the 3.6 weight, and how much water should be used when mixing these.



A 3.6 % NaCl solution has 3.6 grams of sodium chloride dissolved in 100 ml of solution

Pour the water it into a graduated cylinder or volumetric flask containing about 80 ml of water. Once the sodium chloride has dissolved completely (swirl the flask gently if necessary), add water to bring the ***volume*** up to the final 100 ml. **Do not** simply measure 100ml of water and add 10g of sodium chloride. This will introduce error because adding the solid will change the final volume of the solution and throw off the final percentage.

 

A 3.6 % NaCl solution has 3.6 grams of sodium chloride dissolved in 100 ml of solution
Where would one find such solution, is there somewhere we could buy this? As I said before I and probably most of us have nothing to measure the table salt with.

 

No, you make it

On second though sure you do Go to the local drug store and ask the pharmacist to do it for you [smiley=drive.gif]

I forgot, so just in case, so there is no confusion. This 3.6 % solution is to calibrate your refract to SEAWATER. With this solution, on the plate, you want to calibrate it so it reads 35 ppt /or 1.0264. This will cancel the add on A 3.5 % solution would be to check or calibrate it to 35 ppt NaCl, which is what it was set to at the factory. You don't want that.

 

Jeez Boomer I liked it better when you said just to add .001. ;D

Lot's of great info here, thanks for hashing it out.. this is becoming quite a board!

 

Too bad this cant be like horse shoes where just getting close counts !!

 

Jeez Boomer I liked it better when you said just to add .001.

Matt

Yah I know what you mean, just needed to explain things as there seemed to be some confusion. Probably more confused now I know, it sounds like a mess. In short, just use the .001 add on, as we don't know where the accuracy of +/- .001 is at without testing. At times I get carried away and just make it more confusing. I always figure the more I explain the easier it is but often it does not come out that way

Hugio

Too bad this cant be like horse shoes where just getting close counts !!

Getting close is good enough Even if you did not use the add on, it is no big deal. Reefs are always flucuating on their salinity a bit and as I said not all reefs are at 35 ppt

 

Hugio
Who is Hugio? LOL