Live Aquaria salt

[AlanM]

Today’s test after letting it sit for 4 hours.

 

SG: 35ppt

DKH: 9.9 (177ppm)

Ca: 460ppm

Mg: 1480ppm

 

So substantially different from last night, but still near the high end of the range they quote on the bag. Maybe within the range when accounting for measurement error, which I can’t quantify.

 

I tested alk twice and Ca twice and got consistent numbers, though. Also rechecked SG after water tests and still 35ppt.

[Viktoriia]

If there was ever a reason to join the club this thread is it. I love how everyone is pulling resource to test / debunk a new product on the market!

[madweazl]

Today’s test after letting it sit for 4 hours.

 

SG: 35ppt

DKH: 9.9 (177ppm)

Ca: 460ppm

Mg: 1480ppm

 

So substantially different from last night, but still near the high end of the range they quote on the bag. Maybe within the range when accounting for measurement error, which I can’t quantify.

 

I tested alk twice and Ca twice and got consistent numbers, though. Also rechecked SG after water tests and still 35ppt.

Wow, I certainly didn't think there would be that much variation from your initial test. The sample I sent you should arrive on Saturday but it looks like there might not be a whole lot of need for it now   Always nice to get a sanity check though. 

[Origami]

In reading the thread, the endpoint pH doesn't seem to matter a whole lot, correct?

 

 

So I'm not a chemist, but I don't think the actual pH number matters if you're doing a titration test using an acid and a pH probe.  This is what those automated alk testers do. 

 

I believe the raw number doesn't matter, just the point at which the curve changes.  Basically the point at which all carbonate is used up by the acid if I'm remembering it correctly.

 

The pH of the solution should matter when doing a color test for alkalinity with an indicator chemical, though.

 

The endpoint pH is actually very important. That number can shift and, even when titrating, there's normally a number that you're aiming for - somewhat qualitative - that represents a "knee" in the pH curve. (See Figure 1 here.) At that point, it's assumed that all of your carbonate alkalinity has been "consumed" by the acid and, using the amount of acid that you put in during the titration, one can calculate the alkalinity. I don't know if you took high school chemistry, but if you did, you probably did at least one lab that had to do with titrating an acid into a base (or vice versa) while using some sort of indicator solution (phenolphthalein) that changed color at a some target pH.

 

To illustrate, pick a pH level in Figure 1 (from that last link) as your endpoint (say, 4.5) and draw a horizontal line across the graph. Now, retrace that black curve in the figure - one moving up and another moving down a small amount, say 0.2 pH units. Now look at how the horizontal line - your setpoint - is reached at the two extremes of cuve placement. Let's draw vertical lines to the x axis and see the difference in the amount of acid used to reach that setpoint. Let's label that W1. That's the potential error range in your measurement from using that set point. Now, let's do the same thing for another setpoint. Say, 3.8. Going through the same process, we get a different width (W2) for the potential measurement range at this setpoint.  Rather than imagining, though, I used Paint to put this diagram together:

 

 

So why don't we just use the higher setpoint? Because that's not really the point where all the bicarbonate alkalinity is used up. That point is further to the right where the pH begins to flatten out a second time down between pH 3 and 4. If you make the setpoint too high, then you tend to underestimate the alkalinity. If you set it too low, then you're more sensitive to pH shifts in your sample. 

 

In a colorimetric test, though, you don't titrate to an endpoint. So you don't have the benefit of over-titrating and looking for the knee in the curve. Instead, you add a pH indicator along with a calibrated amount of acid, and you estimate where on a "model" titration curve that your sample is at and, from that, you estimate what the alkalinity is in the sample. The problem is, the titration curve (and the endpoint) can shift a little relative to the model and introduce error. But the amount it shifts, according to that RC link that I provided above, is normally not of consequence to a hobbyist (they're saying it's less than 1 dKH, and back then that was about the resolution that we had.). 

 

Years ago, I read a few articles on CO2 and ocean acidification. From that and from equations in the various papers, I tried to build a model in Excel to illustrate the effect of CO2 concentration on pH at various levels of alkalinity.  My interest was to see how CO2 in my house affected the pH in my tank. (For example, in a recent thread, Tony measured a pH of 8.22 and has an alk level of about 6,8 dKH, which is about 2.5 meq/liter. These curves would indicate that his tank CO2 level was what you'd expect if the atmospheric CO2 concentration was 440 ppm or so.) Here's the set of curves that I produced from that. (Disclaimer: I have no idea if the absolute placement of the curves is accurate. However, I believe that the relative positioning of the curves is indicative of what should be expected.)

 

 

Now, the thing to take from this graph is this: Alkalinity and dissolved CO2 concentration shift the pH in the water. And, if you're using an indicator that's basically sensitive to pH to estimate alkalinity from a single point measurement, differences in the pH of the water sample can affect your alkalinity measurement. Dissolved CO2 will not, however, actually change your alkalinity.

[madweazl]

Sample of salt AlanM sent:

 

Sg - 1.026

dKH - 9.2 

Ca - 495

Mg - 1410

 

Water set seven hours prior to testing

Edited October 15, 2017 by madweazl

[Origami]

Today’s test after letting it sit for 4 hours.

 

SG: 35ppt

DKH: 9.9 (177ppm)

Ca: 460ppm

Mg: 1480ppm

 

So substantially different from last night, but still near the high end of the range they quote on the bag. Maybe within the range when accounting for measurement error, which I can’t quantify.

 

I tested alk twice and Ca twice and got consistent numbers, though. Also rechecked SG after water tests and still 35ppt.

 

 

Sample of salt AlanM sent:

 

Sg - 1.026

dKH - 9.2 

Ca - 495

Mg - 1410

 

Water set seven hours prior to testing

 

I'd say that these numbers are within a reasonable range of one another, so testing is not likely to be the issue with that bag of salt that you have madweazl.....

[AlanM]

OK.  Just tested the salt madweazl sent to me.  

 

SG: 35

Alk: 9.86 (176ppm)

Ca: 480

Mg: 1440

 

Water sat for 4 hours before testing.

 

So I'd say that the sample you sent to me is similar to my salt.  

 

I can't explain those super high results you got when you first tested yours.

[madweazl]

Ca was within 40 and Mg within 60 so not too much different given they're different kits performed by different people. 

[Viktoriia]

So the big question is would you use this salt or stick with reef crystals?

[madweazl]

So the big question is would you use this salt or stick with reef crystals?

I ordered a 200g box of IO today with the $25 gift certificate I got for the LiveAquaria salt

[Origami]

I thought that I'd follow up on this with just one other thought: If you're taking a water sample from your saltwater mixing station, make sure that you don't have tiny microparticles of calcium carbonate suspended in the water by turning the mixing pump off and letting the water sit still for several hours. Small particles can mess up both calcium and alkalinity test readings, giving you higher numbers than expected. I was reminded of this the other day when I tested my newly mixed saltwater shortly after running the mixing pump when I got alkalinity numbers 50% higher than expected. So let the water sit so particles can settle, or filter it through some filter paper or a couple of  coffee filter layers.

[madweazl]

I thought that I'd follow up on this with just one other thought: If you're taking a water sample from your saltwater mixing station, make sure that you don't have tiny microparticles of calcium carbonate suspended in the water by turning the mixing pump off and letting the water sit still for several hours. Small particles can mess up both calcium and alkalinity test readings, giving you higher numbers than expected. I was reminded of this the other day when I tested my newly mixed saltwater shortly after running the mixing pump when I got alkalinity numbers 50% higher than expected. So let the water sit so particles can settle, or filter it through some filter paper or a couple of  coffee filter layers.

 

Interesting, never thought about that. I had the pump running in the first bucket I tested but not on the second. The second bucket actually had higher numbers than the first but was also mixed separately (though both to as close to 1.026 as I'm capable of doing) so there would likely be some variation as well. 

[AlanM]

That has never occurred to me either.  I only mixed up 500ml of it in a 1000ml beaker, so errors due to insufficient mixing within a bag would affect me for sure, but I wouldn't get the effect of fine calcium particles floating around.  

[Origami]

Interesting, never thought about that. I had the pump running in the first bucket I tested but not on the second. The second bucket actually had higher numbers than the first but was also mixed separately (though both to as close to 1.026 as I'm capable of doing) so there would likely be some variation as well. 

 

 

That has never occurred to me either.  I only mixed up 500ml of it in a 1000ml beaker, so errors due to insufficient mixing within a bag would affect me for sure, but I wouldn't get the effect of fine calcium particles floating around.  

 

It's only an issue if you have calcium carbonate precipitate floating around. And sometimes you may get some combining in the salt mix (especially if an open bag has been subject to high humidity for an extended period of time) or some of the stuff that plates on the sides of our mixing barrels. In most all cases, if you have a problem with it, the water will be a little cloudy. I just mentioned it because I suspected that is what I was seeing in my instance.

[madweazl]

Did a 10g water change (approx 13%) with the Live Aquaria salt to use it up yesterday and test alkalinity before and a couple hours after the water change; it remained the same (139 before and 140 after with both being 7.8). I usually get a .3 dKH increase with the same amount of Reef Crystals so that was a plus. This salt may still have a use for me after all. I didn't check calcium but I'm sure it climbed a bit more. 

[madweazl]

$38 for the 205g box right now at Dr F&S. 

[D805]

$38 for the 205g box right now at Dr F&S. 

Not a bad price. So are you still using this salt? Would you recommend it?

[madweazl]

Not a bad price. So are you still using this salt? Would you recommend it?

I only used the one bag and went back to Instant Ocean. For the price, I wouldn't hesitate to use it again but when it is at the regular price ($62 I think), I'll just stick to Instant Ocean.