Kalkwasser Weight

[spsick]

Randy, I’m struggling to find the info but I recall you knowing the difference between dense and fluffy kalks?

Looks like BRS as an example is much heavier than others. Are there weight guidelines for kalk? All I know is the generic guideline of 2 tsp/gallon.

 

[Miami Reef]

I’m not Randy, but I have quotes from him.

There's an exact weight amount of calcium hydroxide (1.5 g/L) or calcium oxide (1.14 g/L) that will dissolve in water at a fixed temperature, but for most purposes, 2 teaspoons of calcium hydroxide per gallon of fresh water is about the solubility limit at 25 deg C.

2. The BRS material may be fluffier (lower bulk density), making it less potent per teaspoon than a less fluffy material.

 

[spsick]

Interesting thanks @Miami Reef

I actually have 2 containers the same size. BRS says 2lb while ESV says 14oz. They both recommend 2 tsp/gal. But that makes the BRS over 100% heavier so seems like a pretty big margin.

 

[Miami Reef]

Just FYI, Randy wasn’t saying the BRS kalk was dense or not dense. He was trying to give plausible scenarios for why one person observed their BRS kalk less potent. I shared the quote to show how powder densities can affect how many tsp are actually required.

Here’s the full thread:

https://www.reef2reef.com/threads/avast-marine-kalk-observation.988253/#post-11426232

 

[Miami Reef]

I actually have 2 containers the same size. BRS says 2lb while ESV says 14oz. They both recommend 2 tsp/gal. But that makes the BRS over 100% heavier so seems like a pretty big margin.

It would be interesting to see how many grams 2 tsp weighs per brand.

 

[spsick]

It would be interesting to see how many grams 2 tsp weighs per brand.

I’ll compare tonight.

@Randy Holmes-Farley I gather I should go by weight and ignore volume in this scenario? I suspect using too much would just precipitate but tough to know with the ESV being so much fluffier what the ceiling is.

 

[Randy Holmes-Farley Verified Community Expert]

Weight is always a good way to go. Volume depends on the manufacturing process.

 

[MeganV]

I always.... estimate? I'm just going to saturation so I add more than the minimum amount, then decant the supernatant into my dosing bin, like, as carefully as I can. I'm typically only making a gallon at a time, so I add 7-10 grams with a reasonable kitchen scale with 0.5g resolution and Bob's your uncle.

 

[spsick]

@Miami Reef or anyone else curious in the future:

BRS: 4.1g/tsp
ESV: 2.5g/tsp

So the guidelines of 1.5tsp BRS or 2tsp ESV, Avast, etc per gallon are pretty close.

The BRS one I have had been open for a while so sure it could be a tad heavy from moisture but it’s close given the weight difference of 2 containers the same size.

 

[Randy Holmes-Farley Verified Community Expert]

I always.... estimate? I'm just going to saturation so I add more than the minimum amount, then decant the supernatant into my dosing bin, like, as carefully as I can. I'm typically only making a gallon at a time, so I add 7-10 grams with a reasonable kitchen scale with 0.5g resolution and Bob's your uncle.

Nothing wrong with adding extra. I did that for years. Each batch I stirred up the old stuff and added more if needed based on attaining my conductivity target for the kalk.

 

[Miami Reef]

Nothing wrong with adding extra. I did that for years. Each batch I stirred up the old stuff and added more if needed based on attaining my conductivity target for the kalk.

Why is conductivity better than pH for measuring the potency of calcium hydroxide?

 

[Randy Holmes-Farley Verified Community Expert]

Why is conductivity better than pH for measuring the potency of calcium hydroxide?

in both cases, I recommend comparing the potency of an unknown kalk solution to a guaranteed saturated solution (say, 2 teaspoons calcium hydroxide in a cup of ro/di, stirred well. Essentially using that as the standard (it actually is a recognized pH standard).

The uncertainty in the difference of two hobby pH measurements is probably not a lot better than 0.1 pH units based on just watching a pH meter value drift around. Due to the log scale, that is a potency difference of about 26%.

The uncertainty in conductivity between two measurements around 10 mS/cm is likely much better than +/- 1 mS/cm. I see little drift in this range. That gives an error of less than 10%, and with meters I use it is much better than that.

 

[Miami Reef]

Awesome! Thank you very much.