Boomer / Randy - Please help me understand dissolving salt
- Thread starter Mr31415
- Start date
Billybeau1
Premium Member
I see two problems here. Help me understand.
How do you measure specific gravity ?
How do you measure alkalinity ?
How do you measure specific gravity ?
How do you measure alkalinity ?
Mr31415
Active member
HowardW - because my first tank was started similar to this one. In 24 hours ALL salts dissolved and my calculated and actual salinity readings matched perfectly. The guy who started that tank for me actually dumped all the salt on top of the dry substrate, then filled everything with water.
Furthermore 28kg of salt (which is the "missing" amount) is quite a lot - the flow in the tank does not disturb any sand particles but it does pick up salt particles lying on the bottom - which are obviously lighter. So I cannot see how the salt can creep into the sand without dissolving. But this is just my opinion - I could be wrong.
marsh - the cloudiness is VERY fine but coarse enough that if I look real closely I can vaguely see it swirl in the water column - which means it cannot be that tiny. In other words, looking very closely I can see how it flows through the water column.
Billybeau1 - SG I measure using both my calibrated refractometer as well as a calibrated Hanna electronic meter. Alkalinity is measured using titration via the Tropic Marine kit.
HowardW - I have indeed - but unfortunately the first three buckets of salt were all dissolved in the tank - so if it was a couple of bad batches I have no way to verify that. I have however purchased another bucket - same kind of salt - and that does indeed make the right salinity water - I measured it by making some water in a separate container. Both the refractometer and the electronic meter measured the expected value. At least I am sure now the test equipment is working fine.
Furthermore 28kg of salt (which is the "missing" amount) is quite a lot - the flow in the tank does not disturb any sand particles but it does pick up salt particles lying on the bottom - which are obviously lighter. So I cannot see how the salt can creep into the sand without dissolving. But this is just my opinion - I could be wrong.
marsh - the cloudiness is VERY fine but coarse enough that if I look real closely I can vaguely see it swirl in the water column - which means it cannot be that tiny. In other words, looking very closely I can see how it flows through the water column.
Billybeau1 - SG I measure using both my calibrated refractometer as well as a calibrated Hanna electronic meter. Alkalinity is measured using titration via the Tropic Marine kit.
HowardW - I have indeed - but unfortunately the first three buckets of salt were all dissolved in the tank - so if it was a couple of bad batches I have no way to verify that. I have however purchased another bucket - same kind of salt - and that does indeed make the right salinity water - I measured it by making some water in a separate container. Both the refractometer and the electronic meter measured the expected value. At least I am sure now the test equipment is working fine.
Billybeau1
Premium Member
One should NEVER a water to the salt. Always salt to the water. You risk precipitating your calcium out of solution with the former.
I'm trying to understand your cloudiness problem. How long after a water change does it go away. If you are seeing particles, it is not precip. Precipitation is just cloudy.
I'm trying to understand your cloudiness problem. How long after a water change does it go away. If you are seeing particles, it is not precip. Precipitation is just cloudy.
At your current salinity of ~1.020 your alk should be ~ 5.1 dKH...assuming your usual dKH for TM @1.024 is ~8.2. Checking alk after filtering through coffee filter be in the ~5.1 range....i.e. you are getting a false high reading. My dKH assumption may be wrong...but the concept probable is not.
Mr31415
Active member
Billybeau1 - I know - as I said that tank was started by another person - not me. If you read the link in the beginning you'll see I added the salt to the water.
Please read the linked thread at the top of the page as everything is discussed there. It is a new setup - no water changes. Tank was filled with 14cm DSB and then 2000l RO/DI water was added. Once flow was configured and closed loop running, I slowly (over 3 hours) added 68kg of salt to the tank, cup by cup, whilst the Tunze Stream was dispersing it in to the watr column.
I am not seeing particles - I am seeing something similar than smoke in air...
Please read the linked thread at the top of the page as everything is discussed there. It is a new setup - no water changes. Tank was filled with 14cm DSB and then 2000l RO/DI water was added. Once flow was configured and closed loop running, I slowly (over 3 hours) added 68kg of salt to the tank, cup by cup, whilst the Tunze Stream was dispersing it in to the watr column.
I am not seeing particles - I am seeing something similar than smoke in air...
Billybeau1
Premium Member
Mr, I'm a simple guy. I'm not into grams and weigh and all that stuff.
Take one gallon of ro/di and dissolve 1/2 cup of salt in it and test s.g. Then see how much more it takes to get to 1.025
Most salts require 1/2 to 3/4 cup per gallon.
Take one gallon of ro/di and dissolve 1/2 cup of salt in it and test s.g. Then see how much more it takes to get to 1.025
Most salts require 1/2 to 3/4 cup per gallon.
Mr31415
Active member
Billybeau1 - that is my problem. Stated in simple terms:
When I take 36g and dissolve it in to 1l of RO water in a mixing container I get 1.025 with my salt - which is correct.
If I take 68kg and pour it in to my tank with lots of flow and 2000l of RO/DI water (which is the same relationship than 36g per litre), I expect to see 1.025 but instead I got 1.014.
And the water is cloudy.
That is my problem.
Second problem is how to solve it. Should I carry on adding more salt the way I am doing - to a mixing container and then adding it back to the main tank, or should I wait and maybe in a week's time the precipitate (if that is what it is) will magically cause my 1.014 number to jump to 1.025?
When I take 36g and dissolve it in to 1l of RO water in a mixing container I get 1.025 with my salt - which is correct.
If I take 68kg and pour it in to my tank with lots of flow and 2000l of RO/DI water (which is the same relationship than 36g per litre), I expect to see 1.025 but instead I got 1.014.
And the water is cloudy.
That is my problem.
Second problem is how to solve it. Should I carry on adding more salt the way I am doing - to a mixing container and then adding it back to the main tank, or should I wait and maybe in a week's time the precipitate (if that is what it is) will magically cause my 1.014 number to jump to 1.025?
Billybeau1
Premium Member
OK, so that sounds more like precipitate to me. You are precipitating calcium for some reason. Maybe try reading Randy's article about the subject. Maybe something will click.
What is precipitate in my reef aquarium
http://reefkeeping.com/issues/2005-07/rhf/index.htm
In terms of precipitation during mixing, the concentration of ions and alkalinity rise linearly with rise in salinity. The supersaturation (omega) of calcite and aragonite, however, is not linear with salinity but appears to have a sigmoid curve for standard seawater. At sg 1.017, omega is somewhere between 2 and 4...significantly below the usual 6 or so. What this means is that likelihood of calcium carbonate to precipitate during the dissolving phase is unlikely unless there is a nidus for crystallinization such as a fresh aragonite surface (i.e. sand or other CaCO3 crystals). My guess is the fine particulate cloud you see is an insoluble precipitate of aragonite on the surface of a nidus. After ~24hrs. the salt should have dissolved.
If my guess is correct, the linear relationship between your salinity and major ions will be skewed from normal. If you filter out the particles and measure parameters, I think your major ions Ca, Mg, and Alk will be abnormally low for salinity.
If my guess is correct, the linear relationship between your salinity and major ions will be skewed from normal. If you filter out the particles and measure parameters, I think your major ions Ca, Mg, and Alk will be abnormally low for salinity.
Mr31415
Active member
"In this series, calcium and magnesium carbonate are the first to precipitate, appearing at a specific gravity of about 1.140, which is about a 50% solution of salt in water.1 Such conditions may well exist on the bottom of a saltwater reservoir as the salt is dissolving."
That sounds plausible... If Ca and Mg precipitated out then it could account for the fact that my Ca is only 452mg/L and not > 500mg/L as it usually is with Tropic Marine Pro Reef...
"With some mixes (but not the Instant Ocean that I use), the initial pH on dissolution may be very high (pH 8.5-9 +). As shown in detail later in this article, pH can play a dominant role in determining the rate of calcium carbonate precipitation, and such a high pH would make it more likely to precipitate."
That is also plausible. I know as I was adding the salt the pH was about 8.8 - 9.0, then with time it fell to 8.4. Though I had my huge skimmer running the whole time which should have reduced this effect...
That sounds plausible... If Ca and Mg precipitated out then it could account for the fact that my Ca is only 452mg/L and not > 500mg/L as it usually is with Tropic Marine Pro Reef...
"With some mixes (but not the Instant Ocean that I use), the initial pH on dissolution may be very high (pH 8.5-9 +). As shown in detail later in this article, pH can play a dominant role in determining the rate of calcium carbonate precipitation, and such a high pH would make it more likely to precipitate."
That is also plausible. I know as I was adding the salt the pH was about 8.8 - 9.0, then with time it fell to 8.4. Though I had my huge skimmer running the whole time which should have reduced this effect...
Billybeau1
Premium Member
Now we're getting somewhere. :thumbsup:
I buy the localized supersaturation in part. You have such a massive loss of salt ~25kg. In Randy's article, his trash can has a relatively thin layer after multiple mixes over months.
I am a bit more doubtful of the pH idea given the intial pH you had was ? on RO/DI water which gives inaccurate pH results.
Anyway, if the cloud is precipitate...the mass of it is quite high. You may want to filter it with a sock rather than have it drop onto your substrate.
You will have lost a substantial portion of Ca, Mg, and Alk. Even when you get the sg to 1.024 they will still be out of whack if the water is clear.
I am a bit more doubtful of the pH idea given the intial pH you had was ? on RO/DI water which gives inaccurate pH results.
Anyway, if the cloud is precipitate...the mass of it is quite high. You may want to filter it with a sock rather than have it drop onto your substrate.
You will have lost a substantial portion of Ca, Mg, and Alk. Even when you get the sg to 1.024 they will still be out of whack if the water is clear.
Mr31415
Active member
PS I have recalibrated my Hanna and it reads 1.0188 instead of 1.0195 so it was pretty close...
Anyways I am going to filter the stuff out then re-measure everything.
marsh - how do I filter the precipitate out? What should I use? It is late at night so I cannot go to the shops...
Anyways I am going to filter the stuff out then re-measure everything.
marsh - how do I filter the precipitate out? What should I use? It is late at night so I cannot go to the shops...
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