Reef Chemistry Question of the Day #8

[tyler1503]

At least we know you didn't see it first.

True, plus I didn't get it right so there's some more proof I didn't see it haha

 

[Randy Holmes-Farley]

haha, I just found this place and signed up a few days ago and seen this, then decided to take a shot at it today since there still weren't too many replies.

I used the same rational, and was most questionable about the order of A&B (BTW you have the A & B rationals switched ) but again thought the same - there's more chloride than sulfate so it'd be a smaller change.

That said, I learned this stuff from reading (and re-reading, til it started to make some sense to me lol) your articles Randy, so hats off to you! :insertbeersmileyhere:

Thanks, and welcome to R2R!

I did accidentally swap A and B in my explanation, which I now fixed.

 

[Randy Holmes-Farley]

Ahhha, I see. So would it be safe to say that the balance between the sulfate & chlorine is more important than the value? (With regards to elevated sulfate)

Sorry to take this thread off topic but I do have one question: what's your thoughts on Balling Classic without the sulphate? Good/bad? Long term/short term?

There is actually almost no data on how important the actual amount of chloride and sulfate actually is, so really, the distinction between A and B is an opinion.

But here's a more detailed rational.

Chloride starts off at about 19,400 ppm, sulfate as 2700.

Adding 100 ppm magnesium as magnesium chloride boosts chloride by about 290 ppm, or a rise in chloride of 1.5%. No change in sulfate.

Adding 100 ppm magnesium as magnesium sulfate boosts sulfate by about 395 ppm, or a rise in sulfate of 14.6%. No change in chloride.

So that is the rational for thinking the sulfate alone causes a bigger change (fwiw, analysis of the Cl-/SO4-- ratio change also picks sulfate as the bigger change).

 

[Randy Holmes-Farley]

Ahhha, I see. So would it be safe to say that the balance between the sulfate & chlorine is more important than the value? (With regards to elevated sulfate)

Sorry to take this thread off topic but I do have one question: what's your thoughts on Balling Classic without the sulphate? Good/bad? Long term/short term?

I frankly don't understand why one wouldn't incorporate sulfate into such a recipe. It makes no sense to me. It is not expensive. People can even DIY with Epsom salt from a drug store, so I don't see what is to be gained by ignoring it.

That said, there is little data on what happens when sulfate is elevated or depleted relative to NSW levels of about 2700 ppm.

 

[ksed]

Adding 10 parts by weight of magnesium chloride hexahydrate and 1 part by volume magnesium sulfate heptahydrate to boost magnesium by 100ppm.

Randy, I noticed you have magnesium chloride by weight and magnesium sulfate by volume. Would we be able to use the magnesium chloride in volume. So to keep it simple 10 teaspoons of chloride and 1 teaspoon of sulfate.
If using weight the ratio would be 7.1 to 1 .

Thanks

Kevin

 

[Randy Holmes-Farley]

Adding 10 parts by weight of magnesium chloride hexahydrate and 1 part by volume magnesium sulfate heptahydrate to boost magnesium by 100ppm.

Randy, I noticed you have magnesium chloride by weight and magnesium sulfate by volume. Would we be able to use the magnesium chloride in volume. So to keep it simple 10 teaspoons of chloride and 1 teaspoon of sulfate.
If using weight the ratio would be 7.1 to 1 .

Thanks

Kevin

Oops, that was an oversight (and I'll change it now). Both should be volume. If it was on the weight basis of the hydrated salts, one would use about 7.9 to 1 (which is the 7.1:1 weight ratio of actual chloride to sulfate in seawater corrected for the different percentage chloride in magnesium chloride vs the percentage of sulfate in magnesium sulfate).


This blurb from one of my articles explains where the 7:1 comes in in relation to the 10:1. Note that anything close to 7:10 to 12:1 is going to be fine and better than either alone would be. It is not a critical issue.

Recipe rational:

A certain mixture of magnesium chloride and magnesium sulfate has no net effect on seawater's major anions (chloride and sulfate). All that is necessary for such a recipe is to add these two ingredients in such a ratio that they add chloride and sulfate in the ratio naturally present in seawater (which is 7.1 to 1 on a weight basis and 9.6 to 1 on a per ion basis).


To perfect such a recipe, it's imperative to know the amounts of sulfate in Epsom salts (39%), the amount of chloride in magnesium chloride hexahydrate (34.9%), and their bulk densities, because most aquarists will use a volume based measurement (1.05 g/cm3 for Epsom salts and 0.85 g/cm3 for magnesium chloride hexahydrate solids). Taking all these factors into account, the desired volume ratio is 10:1, MAG flake to Epsom salts, as a supplement; for instance, 10 cups MAG flake and 1 cup Epsom salts.

 

[ksed]

Thanks Randy!

 

[Randy Holmes-Farley]

You're welcome.

Happy Reefing.