Interpreting ICP on saltwater mixed with tap

[zdrc]

I've tried mixing Fritz RMP blue box with my tap. My salifert tests + glass hydrometer (60 deg F calib) give me:

Sg: 1.0245
kH: 8.3-8.9 deg
Ca: 390-400 ppm
Mg: 1410-1440 ppm
pH: 8.0-8.15

I just got ICP results for this. Here they are paraphrased (I've attached the full results)

Important for comparing to my test kit and hydrometer:
Ca: 429 ppm
Mg: 1237 ppm
Na: 8956 ppm
Cl: 23082 ppm

Ones that got warnings:
I: 18.8 ppb -- yellow warning, too low
Co: 0.352 ppb -- yellow warning, too low
Zn: 0.979 ppb -- yellow warning, too low
Mo: 131 ppb -- red warning, too high (~10 times higher than optimimum, 4 times higher than high limit)

I want to know two things,

1. How do I convert the Na and Cl readings to a salinity in specific gravity?
2. Is this Molybdenum level really bad? What does Molybdenum do to livestock?

 

[blaxsun]

I don't think the Mo level is bad per say. Being a trace element having more probably won't really affect anything. The vast majority of your parameters all look good.

 

[Randy Holmes-Farley Verified Community Expert]

Na and Cl alone cannot accurately give salinity unless you assume it is exactly seawater composition, which often isn't true.

Here's a calculator you can use. We can help get the numbers to specific gravity once you have a ppt value:

Compute salinity from sea water macro elements

Method for calculating the salinity of water from water macros elements that can be obtained with an ICP-OES water analysis of our tank.

recifalnews.fr

That water is skewed to excessive chloride and deficient sulfate. IMO, it's not an optimal mix if the values are correct.

 

[zdrc]

Na and Cl alone cannot accurately give salinity unless you assume it is exactly seawater composition, which often isn't true.

Here's a calculator you can use. We can help get the numbers to specific gravity once you have a ppt value:

Compute salinity from sea water macro elements

Method for calculating the salinity of water from water macros elements that can be obtained with an ICP-OES water analysis of our tank.

recifalnews.fr

That water is skewed to excessive chloride and deficient sulfate. IMO, it's not an optimal mix if the values are correct.

Good to know. I put in my macro measurements from the ICP and the calculator says the practical salinity is 35.5 and the density at 68 F is 1.025

I used this converter convert from practical salinity to specific gravity and found that it's 1.0245 at 60F which is exactly what my hydrometer reads. It seems like they agree?

What are the implications of the water being skewed towards excessive chloride? Why do you think this would be the case? Could it be related to the dechlorination process? Does it have to do with the salt or how I mixed it? How far off do you think I am?

 

[Randy Holmes-Farley Verified Community Expert]

Good to know. I put in my macro measurements from the ICP and the calculator says the practical salinity is 35.5 and the density at 68 F is 1.025

I used this converter convert from practical salinity to specific gravity and found that it's 1.0245 at 60F which is exactly what my hydrometer reads. It seems like they agree?

What are the implications of the water being skewed towards excessive chloride? Why do you think this would be the case? Could it be related to the dechlorination process? Does it have to do with the salt or how I mixed it? How far off do you think I am?

I’d be very careful how you interpret the specific gravity from that linked calculator and what temperatures are being used for what fluid.

Seawater at 35.5 Psu has specific gravity above 1.0265.

 

[zdrc]

I’d be very careful how you interpret the specific gravity from that linked calculator and what temperatures are being used for what fluid.

Seawater at 35.5 Psu has specific gravity above 1.0265.

Yes! Sorry I just meant that my hydrometer was reading correctly. It reads 1.0245 in this water and is calibrated to 60 F. The actual specific gravity is slightly more than 1.0265. It looks like adding ~0.002 to my hydrometer reading will give me the approximate salinity at 78 F.

 

[Randy Holmes-Farley Verified Community Expert]

Yes! Sorry I just meant that my hydrometer was reading correctly. It reads 1.0245 in this water and is calibrated to 60 F. The actual specific gravity is slightly more than 1.0265. It looks like adding ~0.002 to my hydrometer reading will give me the approximate salinity at 78 F.

I'm not sure that al makes sense, but as long as you are happy with it, that's fine.

The specific gravity of 35 ppt (PSU) seawater at 60 deg F compared to fresh water also at 60 deg F is 1.0269. I think the calculator is allowing a very nonstandard calculation which appears to be "specific gravity" of seawater at one temp compared to freshwater at a different temp (which is outside the normal definition of specific gravity).

 

[zdrc]

I'm not sure that al makes sense, but as long as you are happy with it, that's fine.

The specific gravity of 35 ppt (PSU) seawater at 60 deg F compared to fresh water also at 60 deg F is 1.0269. I think the calculator is allowing a very nonstandard calculation which appears to be "specific gravity" of seawater at one temp compared to freshwater at a different temp (which is outside the normal definition of specific gravity).

I was under the impression that the calculator was telling me what specific gravity a hydrometer/refractometer calibrated to 60 F would read for 35.5 ppt water at 78 F. This would make the most sense, and make the converter the most useful.

I'll take in a sample to my LFS to get an independent test of the salinity anyway.

 

[Randy Holmes-Farley Verified Community Expert]

I was under the impression that the calculator was telling me what specific gravity a hydrometer/refractometer calibrated to 60 F would read for 35.5 ppt water at 78 F. This would make the most sense, and make the converter the most useful.

I'll take in a sample to my LFS to get an independent test of the salinity anyway.

It may very well tell you that. I haven’t worked through the implications of the different temps.

I just wouldn’t use that calculated value to say what the specific gravity of the water actually is.

 

[zdrc]

It may very well tell you that. I haven’t worked through the implications of the different temps.

I just wouldn’t use that calculated value to say what the specific gravity of the water actually is.

Very true!