[APD] Re:Triple PO4 and Apatite solubility

[Neil Frank <aquarian_subjects at mindspring.com>]

Comments on 2 posts
(1)>From: Paul Krombholz <krombhol at teclink_net>
>Subject: [APD] Re:Triple PO4 and Apatite solubility

>I found a solubility value for Ca(H2PO4)2---1.8 grams per 100 ml.

Hmm... that is much higher than I realized. Then why  does it not seem to
dissolve at all when placed in water.  Is there a way to determine the rate
of solubility at different temperatures?

(2)>From: "Jim Seidman" <js5 at seidman_net>> 
commenting on A. Kumar who wrote:
>>        After some more number crunching, I end up
>>with a value of .02mg/L, or .02ppm phosphate....... will be constantly
maintained (by dissolution) even as the plants uptake phosphate.

Seiman replys: "Unfortunately, this isn't really true. Remember that the Ca
and F ions
>aren't going anywhere, at least not quickly. This will inhibit future
>dissolution.
>
>As you get more and more Ca++ and F- in solution, the phosphate
>concentrations will just go down and down. Unless those other ions are
>being consumed too, the phosphate won't stay at a current concentration.
>
>So it still seems that Triple PO4 is not a good solution for fertilizing.

Jim, would any of the phosphate rock dissolve at all if there was a
moderate amount of Ca already in solution. We are talking about an aquarium
not distilled water?

The utility of slow dissolving Triple PO4 is still open in my mind. This is
not the same chemical as phosphate rock Ca5(PO4)3F.
Neil Frank

_______________________________________________
Aquatic-Plants mailing list
Aquatic-Plants at actwin_com
http://www.actwin.com/mailman/listinfo.cgi/aquatic-plants