Sciencemadness Discussion Board

CaCl2 + H3PO4

Dronami_inc - 14-1-2015 at 08:13

Hi, I've got about 25kg of CaCl2 (it asserts that anhydrous) and 35kg of 85% H3PO4.
So I need to get HCl as gas (it will dissolve in distilled water) and Ca3(PO4)2- note that full substituted phosphate salt for further phosphrus production via coal and electric arc. But it will be later.
- Whether is it enough to warm the equimolar CaCl2+H3PO4 mixture? What should be the temperature to get the most substitutied product?
- Do I need to concentrate H3PO4 more than 85% previously?
- Whether HCl will be dry enough to ?

Bert - 14-1-2015 at 08:51

Please give sources for your procedure?

First, dumping the chloride into phosphoric acid won't do you much- You'll need a base such as Sodium hydroxide as well. Even then, I think you end up with hydrated dicalcium phosphate, not tricalcium phosphate-

CaHPO4•2H2O

CaCl2 + H3PO4 + 2 NaOH → CaHPO4 + 2 NaCl + 2 H2O

You could just use Calcium carbonate instead of the Calcium chloride + Sodium hydroxide. Calcium carbonate is very cheap... Save your anhydrous Calcium chloride for dehydrator use, or melting ice.

For tricalcium phosphate from phosphoric acid, perhaps use lime and phosphoric acid.

gdflp - 14-1-2015 at 10:29

I think he wants to use the two chemicals to make HCl. In that case, I don't think that phosphoric acid is strong enough to protonate the chloride ion. Even if it is, I highly doubt that dihyrogen phoshate is strong enough to protonate chloride. Using sulfuric acid or sodium bisulfate is the way to go.

HgDinis25 - 14-1-2015 at 10:39

Actually, HCl can be "easily" made from Phosphoric Acid.
http://www.sciencemadness.org/talk/viewthread.php?tid=17638

Bert - 14-1-2015 at 10:47
Quote:

So I need to get HCl as gas (it will dissolve in distilled water) and Ca3(PO4)2- note that full substituted phosphate salt for further phosphrus production via coal and electric arc. But it will be later.


You're right, looks like HCl is first on his shopping list. Dronami_inc asked the question in a chlorine production thread too, I found.

Best plan your lab first and THEN go buy reagents...



Fantasma4500 - 15-1-2015 at 06:16

recall washing copper coins briefly with vinegar and salt.. it really does work, guess miniscule amounts of HCl were formed
but i dont get why you would first off want HCl gas (destillation apparatus volume limitations?) and then thereafter throw the HCl gas into distilled water? ok perhaps purity, but common HCl has quite alot of impurities in it anyways
i'd say as mentioned in the other thread you use NaCl, perhaps do it with abit more water so you get concentrated liquid HCl

another rather easy route to HCl could be using CaCl2 and H2SO4, CaCl2 in excess, then distilling off the HCl, leaving behind CaSO4 and CaCl2, perhaps H2SO4 if thats what you choose to be limiting factor, entire thing could perhaps if it reacts stoichiometrically quickly just be decanted

Dronami_inc - 15-1-2015 at 09:25

hey, i am looking for specifications on EXACTLY this reaction. Thank you very much but I know many other ways to get HCl too..."Thousands of them :)".
And btw Bert, i didnt say that i hadnt got lab equipment.

Does anybody can tell me smth about this reaction??
And what vessel should I use? Phosphoric acid behaves agressively to glass, esp. in elevated temperatures

woelen - 15-1-2015 at 11:53

I would not use calcium chloride with the phosphoric acid if you want HCl. The calcium phosphate is insoluble and forms a nasty hard to remove cake.

I would take table salt and mix that with 85% H3PO4 and gently heat. This certainly will give you gaseous HCl. I myself did a similar experiment with NaBr in order to obtain HBr (which cannot be obtained in pure form from NaBr and H2SO4) and this worked fairly well. You, however, do need a large excess amount of H3PO4. Expect at most one molecule of HCl from maybe two molecules of H3PO4, not anything better.

You need to heat moderately strong (less than 100 C). This can be done in glass, at less than 100 C the corrosive properties of H3PO4 are not that strong. It is the very hot glass-like metaphosphoric acid, which attacks silicates strongly.

Bert - 15-1-2015 at 13:04
Quote:

Best plan your lab first and THEN go buy reagents...



Quote:

And btw Bert, i didnt say that i hadnt got lab equipment.


Sorry I was not clear. I meant it is best to first plan your LABORATORY PROCEDURE, then acquire the reagents for it.

I don't want to offend, but the thread makes it look like you assumed something should work, bought (a lot!) of the reagents, then afterwards asked here "how do I do this". And when EVERYONE tells you a different way would be better, you insist answers MUST be for only those particular reagents.

Is this the only acid you can buy over the counter wherever you are? I will understand your posts better if so.

I'm lucky, you can buy 90%+ Sulfuric or 32% hydrochloric acids over the counter at my local building supply stores, and 70% nitric is only a little bit harder to find.

chloric1 - 25-7-2015 at 19:37

I think the iron salt route is a very good one. Ferrous sulfate is used for gardening and sometimes ceramics. A crude technical grade should be cheap in largish quatities. Agricola prepared acids with green vitriol.

Zinc halides give off the hydrohalic acids at modest heating. Either some zinc chloride acid solder flux or zinc sulfate mixed with NaCl should work.