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tom haggen
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OTC Phosphoric Acid
Man, I can't believe how big of a slacker I am. With how much school work I need to do there is no reason why I should be posting messages right
now. But here I go, Someone had mentioned that you can obtain Phosphoric acid OTC in another thread so I thought I would do some investigating. I went
down to my local Hydroponics store where I get my 35% H2O2 by the gallon, and looked around. The product they had called PH Down contained a mixture
of citric acid, phosphoric acid, and either ammonium bisulphate or ammonium bisulphite. I'm wondering If I will be able to separate the
phosphoric acid by fractional distillation? I know that citric acid decomposes at a certain temp so I'm wondering how hard this will be. Any
suggestions? I would also like to isolate the ammonium bisulphite cause I might be able to use that for titrations? I might be wrong about that last
part but if anyone knows, let me know so I can hit two birds with one stone. Look out finals here I come!
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Tacho
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Phosphoric acid is sold OTC to prevent rust on steel. Look at your hardware store.
The brand name "Naval Jelly" comes to my mind. I think its an US brand.
Also serch for "rust converter".
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chloric1
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Dont bother
Its not worth it. The temperature your citric acid would decompose the phosphoric acid would etch your glass! Thats right! Modest phosphoric acid
attacks silicates at high temps. ONe method I ponder is adding muriatic acid to saturated TSP to precipitate NaCl. Sure you would still need to boil
excess HCL but the etching of glass would be
negligable until the phosphoric acid is concentrated.
Better still would be vacuum evaporation of the HCL so lower temperautures could be used!
[Edited on 11/29/2004 by chloric1]
Fellow molecular manipulator
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Organikum
resurrected
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Is TSP
- tri-sodium-phosphate
or
- triple-super-phosphate
or this this the same anyways?
confused
/ORG
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vulture
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Why is it that phosphoric acid is used for removing rust from steel? Is it because it passivates iron even when dilute?
One shouldn't accept or resort to the mutilation of science to appease the mentally impaired.
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The_Davster
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It is trisodium phosphate, Na3PO4.
Source: The bag
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Mendeleev
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The rust remover is only 25%, but certain pH down brands contain 75% with nothing else added. It all depends on the brand, because some don't
even have phosphoric acid, they use dilute nitric acid. You just have to look around. Oh, off-topic but interesting, Wink rust remover is 3% HF.
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Mr. Wizard
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Quote:
"Is TSP
- tri-sodium-phosphate
or
- triple-super-phosphate
or this this the same anyways?"
TSP is Tri Sodium Phosphate, except when you buy it in boxes labeled "TSP" , then it is most likely a cheaper non Phosphate detergent
(Sodium Carbonate or Sodium Sesqui-carbonate, or silicate) that the makers have put in a box with a Trade Marked name of "TSP". This little
bit of deceptive advertising takes advantage of the ignorance of most people who buy the product to clean walls before painting them. Checking the
ingredients on the box will guide you. If the label spells out the words Tri Sodium Phosphate, it is most likely a pure product, if it just uses the
initials "TSP", it isn't. Tri Sodium Phosphate has long grain like crystals and shouldn't foam when treated with a mild acid such
as vinegar.
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tom haggen
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Well the stuff at my local hydroponics store is quite nasty indeed. Not only is it mixed with citric acid and ammonium bisulfite, it is contaminated
with some nasty orange dye. So I don't really think I understood any of the answers given other than hot phosphoric acid will etch your
glassware. That is a big fucking no no. Would you be able to separate the phosphoric acid in a vacuum distillation setup? Or would this too destroy
your glass. On a side note just how many solvents out there will destroy your glass? I know NaOH will, and apparently Phosphoric acid will, any thing
else come to anyone’s mind? Being some one that has worked with metal for a few years now I can honestly say I have never seen phosphoric acid used
for removing rust. The only acid I have seen on the shop floor for these types of uses is hydrochloric acid. Now I've seen Nitric acid used in
the metallurgical lab used for etching clean surfaces in order to observe crystalline lattice structures of metal. But no, I haven't seen
phosphoric acid used in the metal shop.
[Edited on 29-11-2004 by tom haggen]
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BromicAcid
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Phosphoric acid doesn't have a boiling point that I'm aware of. It decomposes to pyrophosphoric acid and other polymeric solids, maybe at
very high temps these will distill (>800C) but I'm not certain.
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tom haggen
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When I read the msds on phosphoric acid it stated that the bp of phosphoric acid was about 158C. But this was assuming you had anhydrous phosphoric
acid. Separating the phosphoric acid is starting to sound like a problem that can't be solved,
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BromicAcid
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According to Hawley's Condensed Chemical Dictionary regarding the boiling point of phosphoric acid:
| Quote: | | ... the 100% acid is in the form of crystals, d 1.834 (18C), mp 42.35 C, loses 1/2 H2O at 213C (to form pyrophosphoric acid)...
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Regarding pyrophosphoric acid:
| Quote: | A viscous, syrupy liquid that tends to solidify on long standing at room temperature. When diluted with water it is rapidly converted into
orthophosphoric acid. Mp 54C. Soluble in water.
Derivation: By heating phosphoric acid at 250 - 260C. Further heating produces metaphosphoric acid. |
Regarding metaphosphoric acid:
| Quote: | | Derivation: By heating orthophosphoric acid to redness |
No boiling point in sight from my end, sorry. Although by the end of everything most everything else, the citric acid, ammonium bisulfide, and dye
should all have volatized out, your resulting metaphosphoric acid could then be re-hydrolyzed. I bought some phosphoric acid once for cleaning
stainless steel from a cooking supply place, it had detergents in it and when I tried to heat to get rid of everything it foamed over and the bubbles
caused my glassware to crack.
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S.C. Wack
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Fluorides, hydroxides and phosphoric are the only glass etchers AFAIK. I have seen hot and concentrated phosphoric etch some of my glass in some long
experiments - it looks nothing like what the hydroxides do, btw.
Phosphates are not hard to find around here. The Ca phosphates from the nursery were grey and smelled bad - that did not go well.
Home Depot sells TSP, in a box that says TSP, and is not crystalline. Yet it really is trisodium phosphate. Several other chains only sell "TSP
substitute"s due to the phosphate thing.
The local chemical salvage store has barrels of the mono- and tri- Na phosphates, cheap - no one wants them.
I like it for cleaning glassware, I guess that makes me an environmental terrorist.
[Edited on 29-11-2004 by S.C. Wack]
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Polverone
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I've heated and concentrated phosphoric acid up to the metaphosphoric acid stage a number of times, and never noticed any attack on glassware. If
there was any attack, it was much slower and less noticeable than that of HF or molten hydroxides.
PGP Key and corresponding e-mail address
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Mendeleev
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What about concentrated NaOH solution, will that do anything?
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neutrino
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Polverone: What type of glass is this? Phosphoric acid attacks Pyrex, so you must have some pretty good glass there.
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tom haggen
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What links phosphates to terrorist activity if you don't mind me asking?
EDIT: This topic sounds a little more advanced than I had first anticipated. I guess I will need to learn a few more things about the chemistry of
phosphoric acid before I decide to continue this endeavor.
[Edited on 29-11-2004 by tom haggen]
[Edited on 29-11-2004 by tom haggen]
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HNO3
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At Wal-Mart I can get phosphoric acid in the hardware section. It is sold as Concrete etchant. Never having needed phosphoric acid, I have never
gotten any, so I can't tell you much about it, but the 1 gal. (3.78 L) bottle says its phosphoric acid based.
\"In the beginning, God...\" Wait a minute, God doesn\'t exist!!!!!!!!!! \"OK, in the beginning, ummm, hydrogen...\" Wait a minute, what about the
laws of thermodynamics? \"OK, in the beginning, ummm.....UMMMMM, what\'s left to choose from?
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skippy
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Polverone,
Was the metaphosphoric acid for elemental phosphorus production? If so, I'd love to hear about such activities 
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S.C. Wack
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| Quote: |
What links phosphates to terrorist activity if you don't mind me asking?
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Look on the labels of various cleansers since the 70's and you will probably see "contains NO phosphates". There was a bit of change
when it became widely known that soluble phosphates change bodies of water, or rather what lives (but mostly dies) in them. Certain plants love the
phosphate and cause some sort of oxygen problem IIRC. I'm sure it's in books and on Google.
Given the sewer - er - river that sewage is dumped into around here (on its way to the Mississippi), often raw, I have no qualms about adding an
ounce of phosphate to it. It's too late.
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budullewraagh
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phosphorus is a shady element. i have a book about it called "the thirteenth element: a sordid tale of murder, fire and phosphorus"
interesting book. i think the main reason phosphorus compounds aren't too available is the fact that it isn't too hard to make certian
organophosphates out of them...(ex: tabun, sarin)
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Polverone
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Yes, the metaphosphate production has mostly taken place in the course of attempts at phosphorus production. The most recent time, I was using an
ordinary borosilicate test tube and simply wished to heat the acid as much as I could. The acid was heated until it turned to a solid, and it did not
melt again even at the melting point of the glass. I had some hopes that it might have been dehydrated nearly to P2O5 and that I would get a strong
reaction with water, but there was no such luck. I didn't notice the glass being attacked, though of course the final deformed tube resembled the
starting item very little and I actually broke the glass to free the solid acid. I have also concentrated phosphoric acid (though not to that degree)
in ordinary soda lime glass and not noticed any attack on the glass after it was cleaned out. What is the chemical mechanism of phosphoric acid attack
on glass? I've seen enough references about it to trust that it occurs, but I've had enough experiences to say that it isn't nearly as
aggressive as HF or molten alkali hydroxides.
PGP Key and corresponding e-mail address
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Blackout
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I've found a nitric/phosphoric acid mix at my local hardware store...
How can we synth. phosphoric acid from elemental P?
\"Si vis pacem, para bellum.\"
\"If you wish for peace, prepare for war.\"
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budullewraagh
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depends on your allotrope. if it's white or red you can easily oxidize it. oxidize until you get the anhydride and then add to water
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Magpie
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I'd been wanting some phosphoric acid for some time (just to have it) and knew that Home Depot had a "Phosphoric Acid Cleaner" made by
Aqua-Mix. When I got it home and poured some into a graduated cylinder (to check the sp. gr. by hydrometer) I noticed it was pink! Then I read the
label a little more carefully and found out it contains "cleaners and degreasers." I added a little food grade activated carbon to a few
mL. This eliminated the pink dye but now I'm wondering what other shit is in there and how I might remove it. I checked the MSDS on
Aqua-Mix's website but it only lists phosphoric acid at 23% by volume (which corresponded to my sp. gr. reading btw).
Eventually I want to concentrate some of this acid up to 88% by evaporation. After reading this thread it seems I may want to do this at a reduced
pressure to save my glassware.
If anyone has any suggestions about how I might remove the "cleaners and degreasers" I would apprecitate hearing them.
The single most important condition for a successful synthesis is good mixing - Nicodem
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