Kalk undissolved residual

hkgar · 09/29/2017, 03:15 PM

I am using Kalk, along with a calcium reactor, to dose dKH. I am dosing about 3.5 gallons per day and the saturation level is about 54%. About 1 teaspoon per gallon.

Even though it is less than fully saturated there is still residual that settles out to the bottom of the storage tank (32 gallon brute, with shut off at about 24 gallons)

Vinny Kreyling · 09/29/2017, 05:08 PM

Normal occurrence.
I am told it dissolves better in cold water, sounds wrong but that's what I'm told.

UTCReefer · 09/29/2017, 05:42 PM

I had the same issue, i ended up just dumping all of it after like 6 months. It was 3-4" thick on the bottom of my barrel, and really put my python syphon to the test.

bertoni · 09/29/2017, 05:43 PM

Kalk does dissolve a bit better in cold water. Some residue is normal, in any case. You likely are seeing some impurities, or maybe some of the lime has converted back into calcium carbonate in the presence of air and moisture.

dkeller_nc · 09/29/2017, 07:41 PM

Weirdly enough, almost all calcium compounds are more soluble in cold water than hot. That's why you get lime deposits on the hot water faucets if you live in an area with substantial calcium hardness in your water.

But on the subject of kalk - Jonathon has it correct. Calcium hydroxide (kalk) will spontaneously react with the carbon dioxide in air to form insoluble calcium carbonate, so stored kalk powder that isn't in a perfectly sealed container will gradually convert to a mixture of calcium hydroxide and calcium carbonate.

The same thing happens in a kalkwasser solution - carbon dioxide continuously dissolves in the solution and precipitates as calcium carbonate. That's why it's a good idea to occasionally dump the entire contents of a kalkwasser reactor and restart it with fresh calcium hydroxide/RODI instead of just continuously adding more calcium hydroxide as a top-off.

bif24701 · 09/29/2017, 08:37 PM

Quote:

Originally Posted by dkeller_nc

Weirdly enough, almost all calcium compounds are more soluble in cold water than hot. That's why you get lime deposits on the hot water faucets if you live in an area with substantial calcium hardness in your water.

But on the subject of kalk - Jonathon has it correct. Calcium hydroxide (kalk) will spontaneously react with the carbon dioxide in air to form insoluble calcium carbonate, so stored kalk powder that isn't in a perfectly sealed container will gradually convert to a mixture of calcium hydroxide and calcium carbonate.

The same thing happens in a kalkwasser solution - carbon dioxide continuously dissolves in the solution and precipitates as calcium carbonate. That's why it's a good idea to occasionally dump the entire contents of a kalkwasser reactor and restart it with fresh calcium hydroxide/RODI instead of just continuously adding more calcium hydroxide as a top-off.

Thank you!

That was very useful information. I had been dumping large amount of powder Kalk into my 32 Brute with RODI and some vinegar thinking any extra would settle and can be mixed in with the next batch. I learned however that didn't work because if I didn't add more powder it wouldn't have as much potency. I started measuring more accurately now so that I don't waste any. I have noted though once it is mixed and out the lid on it keeps its potency very well for the 2-3 weeks until it's all used up.

I add vinegar to my RODI/Kalk to ensure I get good potency. The water here in Florida come out the tap ~75-85 and if it sits in my garage before mixing get even warmer. Now I know why though the Kalk mixes much better in winter.

Thank you!!

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dkeller_nc · 09/30/2017, 11:03 PM

You're welcome. One note about adding vinegar. The concentration of calcium in the saturated kalkwasser solution will indeed be higher with the addition of the vinegar than without. But keep in mind that because vinegar is an organic acid, you will be carbon dosing your tank along with the calcium and alkalinity.

That's not necessarily a bad thing if that's your intent, it's just something to keep in mind.

xCry0x · 10/02/2017, 04:37 PM

Watch the air exposure, I used to use a small 5g tank as my topoff container -- naturally it had no lid.

I would add water and stir all the residue up and assume the water was saturated. Wrong. =) woops.

09/29/2017, 03:15 PM	#1
hkgar Registered Member Join Date: Oct 2002 Location: Dewitt MI Posts: 5,051	Kalk undissolved residual I am using Kalk, along with a calcium reactor, to dose dKH. I am dosing about 3.5 gallons per day and the saturation level is about 54%. About 1 teaspoon per gallon. Even though it is less than fully saturated there is still residual that settles out to the bottom of the storage tank (32 gallon brute, with shut off at about 24 gallons) __________________ Gary 180 gallon, 40 gallon sump, 3 250 W MH + 4 80W ATI T5's, MTC MVX 36 Skimmer, Apex controller Aquamaxx T-3 CaRx Current Tank Info: A 2 Barred Rabbitfish, Red Head Salon, Yellow/Purple, McMaster Fairy, Possum, 2 Leopard Wrasses, Kole, & Atlantic Blue Tangs, 2 Percula Clown, 3 PJ and 1 Banggai Cardinalfish , Swallowtail, Bellus and Coral Beauty Angels

09/29/2017, 05:08 PM	#2
Vinny Kreyling Registered Member Join Date: Nov 2002 Location: Miller Place, NY Posts: 7,206	Normal occurrence. I am told it dissolves better in cold water, sounds wrong but that's what I'm told. __________________ 250 gallon mixed reef, 2 Reefbreeder's Photon V 2, Deepwater BLDC 12, DAS EX-3 Skimmer, MTC mini cal, 2-3/4" Sea Swirls, Aquacontroller & 6 Tunze pumps.

09/29/2017, 05:43 PM	#4
bertoni RC Mod Join Date: Mar 2002 Location: Mountain View, CA, USA Posts: 88,616	Kalk does dissolve a bit better in cold water. Some residue is normal, in any case. You likely are seeing some impurities, or maybe some of the lime has converted back into calcium carbonate in the presence of air and moisture. __________________ Jonathan Bertoni

10/02/2017, 04:37 PM	#8
xCry0x Registered Member Join Date: Jul 2011 Location: Martinez, CA Posts: 1,116	Watch the air exposure, I used to use a small 5g tank as my topoff container -- naturally it had no lid. I would add water and stir all the residue up and assume the water was saturated. Wrong. =) woops. __________________ Red Sea Max 250

09/29/2017, 05:42 PM	#3
UTCReefer Registered Member Join Date: Oct 2008 Location: San Diego Posts: 652	I had the same issue, i ended up just dumping all of it after like 6 months. It was 3-4" thick on the bottom of my barrel, and really put my python syphon to the test.

09/29/2017, 07:41 PM	#5
dkeller_nc Registered Member Join Date: Mar 2013 Location: Central NC Posts: 5,062	Weirdly enough, almost all calcium compounds are more soluble in cold water than hot. That's why you get lime deposits on the hot water faucets if you live in an area with substantial calcium hardness in your water. But on the subject of kalk - Jonathon has it correct. Calcium hydroxide (kalk) will spontaneously react with the carbon dioxide in air to form insoluble calcium carbonate, so stored kalk powder that isn't in a perfectly sealed container will gradually convert to a mixture of calcium hydroxide and calcium carbonate. The same thing happens in a kalkwasser solution - carbon dioxide continuously dissolves in the solution and precipitates as calcium carbonate. That's why it's a good idea to occasionally dump the entire contents of a kalkwasser reactor and restart it with fresh calcium hydroxide/RODI instead of just continuously adding more calcium hydroxide as a top-off.

09/30/2017, 11:03 PM	#7
dkeller_nc Registered Member Join Date: Mar 2013 Location: Central NC Posts: 5,062	You're welcome. One note about adding vinegar. The concentration of calcium in the saturated kalkwasser solution will indeed be higher with the addition of the vinegar than without. But keep in mind that because vinegar is an organic acid, you will be carbon dosing your tank along with the calcium and alkalinity. That's not necessarily a bad thing if that's your intent, it's just something to keep in mind.