j_sum1
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Some phosphate questions
I have access to a couple of kilos each of calcium phosphate and iron III phosphate. Meaning I can save them from disposal if I have a use for them.
My interest is in element collecting and I know that the route from phosphate to phosphorous is problematic to say the least. So, the question is
whether they might be reagents for anything interesting or useful.
Phosphoric acid springs to mind but I don't think I actually have any use for that. Besides, the simple route of reacting Ca3(PO4)2 with H2SO4 and
filtering out the calcium sulfate depends on a good supply of sulfuric acid which I don't have.
I have no real thoughts about the FePO4. Is there anything useful here?
Or maybe I should just stir the calcium phosphate into my compost heap and salvage the bottle.
Any suggestions? (I did UTFSE but nothing outstanding cropped up.)
J.
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Bert
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Have you read this?
The chemicals are neither particularly dangerous nor particularly rare. If free and reasonably pure you might as well save them, unless your flower
garden is Phosphorous deprived.
Sulfuric acid is a rather easy home synthesis, see the MANY related threads here.
Start at sulfuric acid and then make your own hydrochloric, nitric, perchloric or phosphoric acids as required...
[Edited on 31-10-2014 by Bert]
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j_sum1
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Thanks Bert. I am making sulfuric acid acid as we speak but not without a couple of difficulties.
(Hydrochloric I can buy easily. The others are more difficult.)
I know that the chemicals are not rare, expensive or dangerous. They are on the dump pile. I want to know if they are worth the effort to pick up
and take space on my shelf. And is it worth using my hard-won sulfuric to make phosphoric? (A couple of litres of phosphoric if I use the contents
of both bottles!) I just don't know that there is a need but I don't want to overlook something obvious and miss an opportunity.
And thanks for the link. Nice bit of chemical history -- some of which I was not aware of.
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gardul
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My thoughts are this. While you may not have a reasons to use it now, in the feature you may. If you have the room why not?
I just made you read this very pointless signature. How does it feel?
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Magpie
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Phosphoric acid will be useful where you need a non-volatile non-oxidizing acid. But if you can readily buy it cheaply then making it is not so
compelling. If you get tired of storing the phosphates you could always use them as fertilizers.
The single most important condition for a successful synthesis is good mixing - Nicodem
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j_sum1
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Ok. Would this work? Could I use conc HCl to produce H3PO4?
Maybe put a beaker of acid with the phosphate in a sealed plasic container and leave for a week or two. Vapourised HCl can react with phosphate to
produce a chloride salt and H3PO4. Yield would be low but if the phosphate is free in reasonable quantity then it won't matter much.
The only question I have is how easy it would be to separate the products. Would phosphiric acid drain away or would it stick to the solds? Also both
CaCl2 and FeCl3 are deliquescent. I am not sure whether this would be an advantage in removing any water that evaporated or whether it would cause
chloride contamination of the phosphoric acid.
It should be easy to separate unreacted phosphate from the chloride. That is, if I want to reclaim the FeCl3.
Anything wrong with my reasoning here? I guess that's one project that would make rescuing these ites worthwhile. Are there other possibilities?
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j_sum1
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Ok, I have decided to salvage this stuff from the disposal heap.
I don't have H2SO4 to burn but can see that making some phosphoric acid to have on hand might be a useful thing.
I do have plenty of HCl and can get more easily. Is there anything disastrously wrong with the procedure I outlined above?
And are there other useful/interesting things that I might do instead of disposing of the excess in my garden?
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HeYBrO
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I wouldn't chuck them out considering you're also in australia. Namely as we have naturally low-phosphate soils and realising excess phosphate is no good. However, i expect that people will not give a moment to consider that individuals over a large scale do have an impact. Just a thought.
Also, phosphate reserves are starting to dwindle, so it could be a future investment 
[Edited on 4-11-2014 by HeYBrO]
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j_sum1
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Quote: Originally posted by HeYBrO  | I wouldn't chuck them out considering you're also in australia. Namely as we have naturally low-phosphate soils and realising excess phosphate is no good. However, i expect that people will not give a moment to consider that individuals over a large scale do have an impact. Just a thought.
Also, phosphate reserves are starting to dwindle, so it could be a future investment
[Edited on 4-11-2014 by HeYBrO] |
Context is everything. High school lab is disposing of some out of date chemicals. Some stuff is a no-brainer -- toxic and dangerous and not needed.
leave it to be disposed of professionally. Other stuff is also a no-brainer. Full jar of sodium thiosulfate, half jar of potassium nitrate -- pick
it up. These phosphates were in the undecided category and there was a reasonable quantity.
Some may make it to my garden eventually, but I am likely to stir it through the compost first. It certainly won't be released into the wild in
concentrated form. But if I can make productive use of it in my lab, that is a higher priority.
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j_sum1
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On the subject of phosphate reserves dwindling... It is not quite as straightforward as that.
Accessible and easily mined reserves of phosphate are indeed going down. Tapping into other reserves is always an option (albeit more expensive.)
But there are other ways that we can get it: primarily by increasing efficiency in the fertilising methods that we currently use. Only a minute
percentage of applied phosphate fertiliser actually makes its way into plants. There is really promising research into phosphate-less agricultural
methods -- including reintroduction of symbiotic fungi to our agriculture. Re-introduction, because they were once commonplace
apparently.
TED talk on the subject
Blog on fungi
Forbes on phosphorus, quoting USGS
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