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Author: Subject: (HPO3)n Dehydrating agent (polyphosphoric or metaphosphoric acid)
chloric1
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[*] posted on 8-9-2005 at 20:10
hehhehehe


Oh Bromic-I didn't include the juicy pictures yet! Wait until you see light come through the bottom of the crucible. This after rinsing out 2 or 3 grams of nickel phosphates with 31% HCl!! I was flabbergasted by how close I came from the bottom from falling out completely and possibly splashing 250 degree acid everywhere.!:o Stay tuned!!1

P.S. Oddly enough my aluminum support ring got a white crust from spatter that rinsed off with water. Maybe aluminum? If not surely aluminum oxide crucibles. I might be suicidel enough to try aluminum metal. But no red heat for the metal. It melts at like 660 C.:(:(




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[*] posted on 10-9-2005 at 08:11
another snag


well I tried another expensive crucbile. an aluminum oxide one. put in about 50ml of 85 % phosphoric acid in the crucible and then applied a propane flame. it cracked loudly instantly! OK this research has set me back $25 now so now I will only use pyrex or fused silica. I am heating 100ml pf the acid in a pyrex beaker now. IT is now reaching the boiling point and I will see how well it holds up. I have alos requested my library obtain a couple articles about glass corrosion, phosphorica acid etc. It wil be a couple weeks before I know details.

Garage chemist, as far as the info I was able to read in the articel abstracts, the thickening in quartz would be caused by the formation of silicon phosphate. this would also explain about using hot NaOH solution as a remedy for this. FOr this would remove this crusty deposit.

Ahh! the acid looks good and is in rapid embolution!:cool: COME ON BEAKER YOU CAN DEWWIT!:P:D




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[*] posted on 10-9-2005 at 08:18


Good luck with that chloric. What about a carbon graphite crucible?
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[*] posted on 10-9-2005 at 08:38


Yes up to 275 degrees C if I can recall. BUt I would make sure it is PURE graphite and not that clay bonded shit. Also, if you can use a kiln,which I cannot, I ve seen lots of article abstracts using alumnium phosphate as a binder in ceramics. Just a thought. hot phosphoric acid bubbeles a little on concrete but mostly becuase of included carbonate. Pure calcium aluminosilicate as a binder for a graohite or better silicon carbide?? I do not know what will work. Right now pyrex works.


Status update. I have not reduced the flame or moved anything and the boiling has slowed down almost entirely. I see period phosphoric acid smoke rise but no major smoking, bumping etc. The beaker is crystal clear and no silicon phosphate can be observed.I have a reduction in fluidic volume of less than 20 % so far. I will wait 20 minutes so the beaker has time to acclimate to its warm environment then I will slightly increase the heat.




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[*] posted on 10-9-2005 at 08:51


What th.?! Alumina is one of the strongest ceramics and it has high conductivity and low expansion. I refuse to believe you cracked it!

Geez, you must've used an oxyacetylene torch at least!?

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chloric1
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[*] posted on 10-9-2005 at 09:38
no only propane


I think these are just not designed for liquids. I think the heating alumina and the cool acid just did not agree. Well, the pryex seems to still be working. I know have a crystaline solid in a VERY thick liquid. I cranked up the heat. wish me luck!



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[*] posted on 10-9-2005 at 10:13
LMAO


A bug had fallen into my evil phosphoric acid stew and from what my digital thermometer says it is about 520 degrees F or about 270C. Not exactly sure I do not have a Celcius measureing device that goes to 300C :mad: But the bug kinda melted and carbonized!:o Both from the heat and maybe the dehydrating solution. I just am getting so crazy that I find it amusing an insect flew to its grizzly demise in my hot polyacid!

[Edited on 9/10/2005 by chloric1]




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[*] posted on 10-9-2005 at 10:42


Like I already said before I have some doubts the metaphosphoric acid could form as low as at 270°C. As already mentioned I heated at an only somewhat lower temperature for 3h under aspirator vacuum and at the end the water was distilling off at a too low speed to be worthy continuing. After weighting the flask the content was practically the theoretical one expected for H4P2O7. So the decomposition ends at the pyrophosphoric acid unless going considerably more extreme. Also without vacuum it seams unlikely the water vapors would be removed faster than they would be readsorbed (unless one really goes to red glowing heat!). To loose more water at a practical speed it seams to me one has to heat at considerably more extreme conditions - perhaps it would get practical at >350°C under vacuum - but that is already more than I would like my flasks to withstand.

[Edited on 10-9-2005 by Nicodem]




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[*] posted on 10-9-2005 at 14:22


Is silicon phosphate soluble in any phosphoric acid?



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[*] posted on 11-9-2005 at 06:22


Nicoderm I believe your right I believe the crystaline material I have is the pyrophosphoric acid. Curiosity aside, I will put a few grams on my pure graphite plate and blast it with my torch. I want to see if I get a glassy material or whatever.



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[*] posted on 12-9-2005 at 22:33


I took a look in the large P supplement of Mellor's vol 8 today. There were a lot of refs but of course the English-language ones on hand were not so interesting, so I'll paraphrase the book, accurate or not.

Au and Pt are the preferred dehydration crucibles...what a surprise. A small amount dissolves, enough to color the acid. Graphite is OK up to 350C, at which point reduction starts. Hastelloy [nonspecific] crucibles were recommended. These were the only materials mentioned specifically as being OK at high temps. There was an IEC article [23, 140 (1931)] on corrosion but this seems to be at less extreme service. Quite a few alloys were tested.

Impurities increase the level of attack.

There is much mention of glass and silica, though quartz is supposed to be the most resistant. H3PO4 concentrations <60% or something are supposed to be OK, but Pyrex/borosilicates are said to be attacked at pyrophosphoric temps. Some soda glasses are more resistant than others, it says. Some glasses form a dissolved silicon phosphate, others get a protective layer.

One reference is summed up by saying that monoammonium phosphate becomes pyrophosphoric acid after heating at 340C for 3 hours. Polyphosphoric acid is formed at 440C, and higher polyacids at higher temps. Also mentioned is that there is no metaphosphoric acid, just mixtures.

I'll take a look at Gmelin's and the available German articles eventually.

[Edited on 13-9-2005 by S.C. Wack]
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[*] posted on 13-9-2005 at 09:06


Have any of you tried to extract the phosphoric acid after heating and separating the different phosphoric acids? Perhaps by calculating how much(if any) metaphosphoric acid one produced you can more accuratly find a correct heat and time.

I got bored so I didn't a little searching here, and came up with a separation proceedure.


Quote:

At the
end of the time allowed for reaction, barium chloride solution
was added to precipitate barium metaphosphate,
which was filtered. To the filtrate ammonium hydroxide
was added to precipitate barium orthophosphate.
Filtration was carried on by suction through a 5.5-cm.
filter in a Biichner funnel. The precipitate was washed
several times with water, then twice with 95% ethyl alcohol,
and finally twice with ether.



Quote:

Separation of these two acids was accomplished by the
procedure of adding barium chloride and ammonium hydroxide,
respectively, to precipitate in turn barium metaphosphate
and barium pyrophosphate.


I had to post the first quote to share the proceedure. The article also says that Metaphosphoric acid was prepared from 85% U. S. P. phosphoric acid by evaporating and finally heating it to a dull red heat for a few minutes. It doesn't mention any sort of crucible material, and I am sure it is nothing you havn't heard yet.

This came from
D. E. Hull;
J. Am. Chem. Soc.; 1941; 63(5); 1269-1272
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[*] posted on 13-9-2005 at 15:02
As far as I can tell copper works.


I made two attempts at metaphosphoric acid today. My first attempt involved naval jelly, which I procured from the hardware store, according to the household products database it is composed of the following:
Quote:
Surfacants 1-3%
Isopropanol 1-3%
Phosphoric Acid 25-30%
Sulfuric Acid 0.1-1%
Water 65-70%
Xynthan Gum 1-3%
Fumed Silica 0.1-1%

So I put that liquid into a copper crucible made by drilling some holes in a large diameter copper endcap. The naval jelly was a bright pink color. I heated cautiously, lots of bubbling started really quickly so I stirred with a graphite rod so that if the bottom was being erroded quickly I would be able to feel it. But it just kept dehydrating and loosing more water. Eventaully it took on a coppery color and I stopped heating. Let it cool and rinsed out the crucible. As far as I could tell it looked great, no pitting, no thin spots, very clean, I guess it only attacked the copper oxide on the inside. So I put more naval jelly into the crucible. And heated with a torch for almost an hour. What I ended up with was a black thick liquid, that when allowed to cool on the stirring rod turned into a reflective glass. When the crucible was cleaned out I noticed no attack though the crucible was oxidized somewhat heavily on the outside, a black flakey film all over it. The first picture in the attached picture is the inside of the crucible after the test run to see if the acid was attacking it, the second picture is just before I shut it off on the second run (notice the color of the crucible and additionally the blackness of the acid is likely due to the organic additives breaking down and such).

My next try at metaphosphoric acid involved heating ammonium phosphate until it completely decomposed. So I put that into the crucible and it was not until it started evolving corpious amounts of ammonia did I remember copper's weakness for ammonia gas. But I pressed on, lots of ammonia being evolved and suddenly (within 5 seconds) it completely stopped. The bottom of the crucible contents solidified and there was no gas evolution. Then shortly after that there was evolution of nitrogen dioxide from the nitrates and such in the fertilizer [Duh.... nitrates and phosphoric acid in a copper crucible, real smart Bromic!] So that died down and the solid shell that had formed melted and I was left with a black liquid. I heated this driving off gasses of all kinds until it would readily solidify upon pulling the stirring rod out of the liquid. I poured it out onto a steel plate and when it solidified it looked just like silver metal, very reflective. When broken it was black in the middle and looked like glass. Adding a piece to water lead to slow dissolution and coloring the water green (iron compounds present in the fertilizer and a nickel stirring rod and copper crucible, take your guess where the color comes from). Slow dissolution is a property of metaphosphoric acid, at least some variaties.

Nothing definate today except as far as I can tell a copper crucible will get you through dehydrating the acid. No attack seen on it except when nitrates are present.

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[*] posted on 13-9-2005 at 19:06


Bromic, I appreciate the help on this research. after my calamities, I needed a little break. I have some pictures of a very syruppy pyroacid that got hot on mixing an equal volume of silfuric acid. I have the mix in a glass stoppered bottle until later. Sunday I could not get it hot enough to give off SO3 and I was really paranoid about busting the flask and getting burnt. I want to construct a sand bath first and retry with a stronger fire.

Second, I have Reagent grade phosphoric acid I purchased when I had money and I will try copper to get the goods on what really happens. Also, a small sheet of Hastelloy from Mcmaster Carr could be beaten into a homebrew crucible.

Thanks again for your valuable input:cool::D




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[*] posted on 14-9-2005 at 18:24


Perhaps we (meaning anyone who feels up to it) could try plating a cheap crucible with pure gold since it was mentioned that a gold crucible is preferred. Since solid gold is out of the question, why not plate? I don't think it would cost more than $10 in Au assuming you have the crucible and the necessary reagents. I'm thinking a cyano-gold complex for electroplating the crucible; I'll have to look around and see what they use in industry for making cheap electroplated jewelry.

I've a couple hundred mLs of 85% phosphoric acid, but I'll wait till I can obtain either platinum labware or gold plate a crucible. Do you think heating it in a helium atmosphere would be beneficial? Seems to be rather hygroscopic and blowing helium over it would remove water vapor and prevent any contamination.

Oh Tim, FYI, pure alumina cracks very easily when you take a flame to it; gradual heating works best with alumina labware.
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[*] posted on 18-9-2005 at 15:34


Could a zirconia crucible be feasibly used?
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[*] posted on 19-9-2005 at 15:38


I'm guessing it could be used yet it might react with the binding material in the zirconia crucible itself (zirconium oxide, plus something to hold it together).

This weekend I plan on trying this experiment using a copper end cap that I will electroplate with a reasonable thickness of fine gold. I hope to get some pictures, perhaps even video of the subsequent heating and hopefully the product formed :)
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[*] posted on 19-9-2005 at 16:59


Very nice. Can't wait to hear the results but it seems that a non-reactive metal route would prove more successful. I definately want to attept as (HPO3)n will prove to be very valuble.
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[*] posted on 13-10-2005 at 19:39
Cu is resistant!.


Alright, yesterday I bought a copper end cap and 4L of concrete etchant.
The etchant/cleaner listed phosphoric acid and dietheleneglycol-monobutyl ether as the only ingredients.
When I got home from the store I poured 80mL of the clear etchant into a 100ml beaker and proceeded to heat it on my hot plate. The etchant frothed and bumped badly at 110°C so I added a few small pieces of gravel which stopped the bumping. However, the frothing continued to get worse until at about120°C, when it overflowed the beaker, hissing and turning black upon contacting the hotplate. Fortunately the ceramic top of my hotplate resisted the hot phosphoric very well so it only suffered minimal damage (about .25 mm was eaten through).
After cleaning everything, I re-attempted to dehydrate 60mL etchant in an 80mL beaker. This time with gentle heating and 3 layers of Al foil on the hot plate. This resulted in the foam overflowing the beaker again, however the Al foil kept the hot plate from damage.
Next I added 50mL etchant to a 300mL beaker and repeated the process, again with fresh Al foil. The phosphoric acid foamed up to the 225mL mark but gradually subsided at 170°C.
The heat was cranked up and the blackening phosphoric acid mixture started to boil gently with no frothing while the temperature rapidly rose. At 340°C I removed the thermometer and let the black liquid gradually cool to room temp. Next I added approx 20mL of the black , syrupy liquid to the copper end cap, placed the cap on my hotplate (with Al foil) and set the heat to max.
The temp rapidly increased to 340°C at which point I removed the thermometer, about 5-7 min after that, the black liquid began to boil again and parts of my hotplate started to glow a dull red .
I was worried about my hotplate so I lowered the heat slightly, but the glowing areas continued to grow and the phosphoric acid bubbled over. When I saw the end cap overflow I knocked it off the hotplate and into the gravel with a board I had handy.
I washed the copper cap and there were no signs of any form of attack, different from what atmospheric oxygen does to copper at those temps.
In conclusion, I believe that copper is sufficiently resistant to phosphoric acid for practical use. By the way, P2O5 can dehydrate amides to nitriles.
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[*] posted on 14-10-2005 at 06:39


yes Cu is resistant, but there are signs of attack!
it turned dark when the HPO3 came in contakt whit the Cu, so it must be a passivation :)
the layer of passivatet Cu dont dissolve in water (just as an information, so u can clean the equipment whit warer ;))
if the H3PO4 alredy turned into pyrophosphoric acid and the same start to turn into HPO3 the stuff is that viscous that droplets start to spray out, so be careful :P
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[*] posted on 14-10-2005 at 20:17


Indeed, there is attack. Although the crucible itself didn't look like it was attacked significantly, upon dissolution of some of the resulting solid metaphosphate in water I found there was an insoluble white component (copper I compounds? polymetric phosphoric acids?) and there was also a bit of what looked like elemental copper powder at the bottom of the test tube, and the water was distinctly blue. Attached is a picture of what I got upon dissolving about 3 grams of my obtained solid in water.

Note that although it did react, the crucible looked fine so since the oleum distills it shouldn't be much of a problem... probably...

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[*] posted on 30-11-2007 at 18:10


Quote:
Originally posted by chloric1
A bug had fallen into my evil phosphoric acid stew and from what my digital thermometer says it is about 520 degrees F or about 270C. Not exactly sure I do not have a Celcius measureing device that goes to 300C :mad: But the bug kinda melted and carbonized!:o Both from the heat and maybe the dehydrating solution. I just am getting so crazy that I find it amusing an insect flew to its grizzly demise in my hot polyacid!

I guess that would be a bit of a fly in the ointment...




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[*] posted on 19-5-2008 at 21:15


This compound really intrigues me, I wish I still had my 500mL of ACS H3PO4 however I disposed of it when I went to college. I'd really like to experiment with this compound again this summer.



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[*] posted on 20-5-2008 at 00:20


Just bought 100g of metaphosphoric acid, for 8 british pounds :D

This seller is awesome:
http://myworld.ebay.co.uk/mordants-2008/
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[*] posted on 20-5-2008 at 06:13


Nice find!



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