warning: hydrochloric acid is corrosive and ammonia gas is toxic. work outside or in a fumehood.
Hi everyone, in this video i'll show you a process to extract calcium phosphate from animal bones; the paper i'm following can be found in description.
To start we put the roasted and grinded bones in an erlenmeyer flask; the bone meal weighs 83g.
The roasting step is necessary to remove any organic material that could interfere with the reactions; to do this i put the bones in a mild charcoal fire for a few hours.
Now 26ml of 32% hydrochloric acid are diluited in 125ml of water and added to the flask.
In this step the acid reacts with the calcium phosphate present in the bones to form calcium chloride and calcium dihydrogen phosphate,
also called monocalcium phosphate, that solubilize due to the low ph.
After the acid addition the solution is stirred for a bit and left to react for a few days; finally the reaction mixture is heated to 80C for about an hour to make sure the reaction is completed; at this point the ph is around 5, so about 5ml of concentrated hydrochloric acid are added to get the ph back to around 2, but this was probably unnecessary.
The dirty liquid is then filtered to get rid of all the insoluble matter and a clear orange solution is obtained. the residue in the filter is washed with 80ml of diluited hydrochloric acid.
If gravity filtration is used this step is quite slow but it can be speed up by replacing the filter paper every once in a while.
The solution is transferred to a larger beaker and an excess of 5% ammonia solution is added and a precipitate is formed.
In the first reaction taking place in this step the ammonia is reacting with the calcium dihydrogen phosphate to produce diammonium hydrogen phosphate and insoluble dicalcium phosphate.
After this, the ammonium phosphate reacts with the calcium chloride present to form more dicalcium phosphate.
The product is then filtered and washed several times with water. after this the phosphate is left to dry for a few days.
But before moving on, if we check the reactions and follow the equations we can see that half of the calcium chloride formed in the first step is still in solution, so to check if the calculations are right and to recover all the calcium from the bones we need to precipitate it.
I choose to use sodium carbonate to do it but sulfuric or oxalic acid can be used instead, the carbonate is just easier to convert to other calcium salts.
As you can see a white precipitate has formed.
Back to the phosphate, after letting it dry we have our final product: 9,2g of dicalcium phosphate dihydrate.
I can't really tell what the theoretical yield is because i don't know the percentage of calcium phosphate in my bone ash and neither i know the purity of the product, but the goal of the video was still achieved.
The calcium phosphate made in this video will be used in a following video to make phosphoric acid and phosphorous.
Thanks for watching.
The paper mentioned in the video: [ Ссылка ]
Music: Midnight Walker - Bohren & der Club of Gore
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