j_sum1 - 27-2-2015 at 17:25
It is nice to get to the end of a project successfully. I thought I would report on a procedure I developed.
Let me stress at the outset that this is by no means sophisticated nor particularly innovative. But it is significant for me since I began it when my
lab consisted of an odd collection of jars, a 2.5L bottle of muriatic acid and an assortment of scavenged chemicals and items from the supermarket.
Procedure:
50g of calcium phosphate was spread over the bottom of an airtight plastic container. A beaker (mug) of muriatic acid (100% excess based on
stiochiometry) was placed in the container and the lid sealed securely.
Set-up was left standing for about two months. During that time the vapour from the acid reacted with the calcium phosphate. The powder at the
bottom of the container changed to a cakey mass that then cracked and then turned to a soft slurry of toothpaste consistency that oozed with
phosphoric acid.
Ca3(PO4)2 + 6HCl --> 3CaCl2 + 2H3PO4
The container was then washed out with acetone. This dissolved the phosphoric acid but allowed the CaCl2 to settle.
It was at this point that I made my most significant mistake. I left the mix sitting around for one month intending to perform a proper distillation.
During this time the solution discoloured; presumably from a reaction between the acid and the lid. I still don't have good distillation equipment
but I am satisfied that it would be straightforward.
The mix was heated to drive off the acetone and absorbed water. High strength phosphoric acid remained.
I am confident that with proper distillation equipment and careful handling, a yield of greater than 90% should be possible.
Again with proper equipment, the majority of the acetone should be recoverable. The calcium chloride byproduct should be able to be dehydrated to a
useful product also.
Sorry, no pix. I was not thinking about reporting anything when I began the experiment. I will attempt another run including a proper distillation
and take photos along the way.
[Edited on 28-2-2015 by j_sum1]