TRUE salt reading

[LFS_worker]

I have been doing alot of experimenting with different chemicals in the reefs and they have on certain testing levels.

There are several things that I have come across that are highly over looked that need some attention. The only one that I have yet to over come is a true salt reading. I'll give some background...

Starting with a refractometer that I normally calibrate at 35ppt I calibrated it down to 0ppm or 1.000sg using ro/di with a tds of 1ppm.
Next step I seperated 2 containers out with 100mL of water and one got 20gm of magnesium sulfate and the other got 20gm MgCl. The water was tested for refractive index and the results were not good. Most dosing of any Mg suppliment will throw off "salinity readings" on a refractometer , and a conductivity probe.

To rectify this I have attempted to make 20g of PURE salt ... but I am having trouble getting my "Hands" on pure molecular sodium. ( For safety if you ever come in contact with pure sodium DO NOT TOUCH IT WITH YOUR BARE HANDS). Then the plan is to "Mix" it with pure clorine gas (easy to get). Once a pure salt is achieved then I can weigh it out and reference a normal salt water at 35ppt, and see what the my reef is actually reading.


anyways im looking for a way to get a true SALT reading from a sample. Thanks
Brian

[bertoni]

Well, proper ocean salinity, conductivity, and SG measurements are a bit more complicated than that. I don't know what you mean by a "true salt reading", but a conductivity meter, when calibrated properly, will be fine. A target of 53 mS at 25 C is the standard "natural ocean water" level, with most conductivity probes having temperature compensation. For salinity, the modern measurement method is usually "psu" (practical salinity units), which is a function of conductivity.

This article might help:

http://www.advancedaquarist.com/2002/1/chemistry

[LFS_worker]

Mg levels with both samples are effect conductivity readings also.
I still have to read the article but thanks
Brian

[bertoni]

Yes, Mg will affect the conductivity and refractive index, but that's what's wanted. The amount of Mg in the water is an important characteristic.

[LFS_worker]

I agree but the company "X" we would like to think that the levels of Mg, Ca, and many other Ions are at NSW levels but I have found that NO brand of reef salt does this. More times than not they are off by a considerable amount.

If the ca, alk, and mg are all low and I mix my salt water to 1.026 @78F then I add it to my tank and then dose Mg, Ca, and ALK accordingly then my refractometer readings are wrong.

The main 4 ions are the largest variables in refractometer readings and conductivity readings I find it quite annoying that if instant ocean got a good deal on an ion that I dont actively test for (i.e. strontium) and they decide to add more to save on salt or Mg that my reef suffers so I want to eliminate the variables and control my true salt levels and I need a pure sample. Or a way to eliminate the variables from the manufacturer.

I hope you can help and thanks for your time!
great article BTW!!!
Brian

[bertoni]

I haven't found a particularly good salt product, either. Sigh!

Technically, a "salt" can refer to any combination of the anion from an acid, and the cation from a base. So the "salt content" of ocean water is not necessarily defined by the sodium and chloride combination. I don't know of any practical way to sort the effects of potassium and sulfate, as two examples, from the effects of sodium and chloride, and I'm not sure what it'd mean.

Testing the calcium, magnesium, and alkalinity levels from a 53 mS solution would be a first approximation of the reasonableness of a salt product.