Chemists: Pellets Containing Calcium Phosphate

[Randy Holmes-Farley Verified Community Expert]

For example:

Calcium phosphate saturation in seawater around the Andaman Island

drs.nio.org

“Ionic product (IP) of calcium phosphate is calculated at some stations around Andaman Island. The depthwise variations of the ionic product of calcium phosphate seem to follow a normal trend with maximum saturation value between 100 to 200 m. Using apparent solubility product of 4 x 10/20 C given by Kester and Pytocowicz. The maximum percentage saturation works out to be 67, 65, 95, and 97 respectively towards west, east, north and south. ”

 

[Dan_P]

It’s more complicated than that. Most phosphate in seawater at pH 8.2 is not PO4 - - - and doesn’t get counted in the ksp.

Also, ion pairing lowers the free phosphate a lot and lowers free calcium a bit.

I found a bottle of calcium phosphate from Loudwolf bought years ago when this subject came up on another big forum. I will probably test the solubility this coming Monday.

 

[Reef Nutrition]

I'm unsure as to the importance of this information for this discussion, but here is more of a breakdown of ingredients.

I don't know enough about the phosphorous or calcium phosphate to be of assistance. All I can do is provide you all with this level of transparency and let the experts break it down. I can tell you that any food you put in the tank will have phosphorous. It's kind of important to all living things.

Best,
Chad

 

[Randy Holmes-Farley Verified Community Expert]

I found a bottle of calcium phosphate from Loudwolf bought years ago when this subject came up on another big forum. I will probably test the solubility this coming Monday.

And the results are? lol

 

[Dan_P]

And the results are? lol

$#@%%&!

Loudwolf Ca3(PO4)2 99% gave me a solubility of 300 mg / L. That is at least 10x higher than expected. I tried rinsing the solid 3X to remove very soluble PO4 contaminants but still getting high PO4 readings. I was thinking of comparing solubility of Loudwolf in RO vs Instant Ocean to confirm there is something odd with Loudwolf material. Any ideas how to unravel this?

 

[Randy Holmes-Farley Verified Community Expert]

Maybe it is not crystalline, but amorphous:

Amorphous Calcium Phosphate​

Amorphous calcium phosphate (ACP) is the first solid phase precipitated after the rapid mixing of aqueous solutions containing Ca2+ and PO3− ions

(I think the po3- is a typo of po4—)

Amorphous Calcium Phosphate - an overview | ScienceDirect Topics

www.sciencedirect.com

Amorphous calcium phosphate (ACP) has high solubility, facilitated by its amorphous structure, the hydrated layer and defects. In particular, the lack of periodic long-range order in ACP allows formation of structural defects thus increasing both rates of solubility and resorption leading to improved bioactivity [6].

Amorphous calcium phosphate materials: Formation, structure and thermal behaviour

Amorphous calcium phosphate (ACP) is essential in formation of mineralized bone and using as a bone substitute. This study presents new aspects of car…

www.sciencedirect.com

 

[Dan_P]

Maybe it is not crystalline, but amorphous:

Amorphous Calcium Phosphate​

Amorphous calcium phosphate (ACP) is the first solid phase precipitated after the rapid mixing of aqueous solutions containing Ca2+ and PO3− ions

(I think the po3- is a typo of po4—)

Amorphous Calcium Phosphate - an overview | ScienceDirect Topics

www.sciencedirect.com

Amorphous calcium phosphate (ACP) has high solubility, facilitated by its amorphous structure, the hydrated layer and defects. In particular, the lack of periodic long-range order in ACP allows formation of structural defects thus increasing both rates of solubility and resorption leading to improved bioactivity [6].

Amorphous calcium phosphate materials: Formation, structure and thermal behaviour

Amorphous calcium phosphate (ACP) is essential in formation of mineralized bone and using as a bone substitute. This study presents new aspects of car…

www.sciencedirect.com

Ding! Ding! Ding!

I was thinking precipitating an insoluble phosphate salt might occlude a soluble phosphate but forgot that such precipitations can produce amorphous solid.

Now I am wondering whether the calcium phosphate used in formulating the Op’s fish food pellets is amorphous.