LesserLordKusanali
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How to slow down reduction of phosphates
Hey guys first post here! So today while I was working on my phosphorus project I've been working on for a long time I had a bit of an explosion. I
used stoimetric amounts of 200 mesh aluminum powder, homemade sodium hexametaphosphate and some silicon dioxide. I can't remember if I added a flux of
NaCl or not. Anyways all the guides and videos show it as a slow process of heating it in a retort and the phosphorus fumes condense underwater. I
tired this once but was unable to reach the required temp to reduce the phosphate to elemental phosphorus (probably a good thing too as you'll see in
a sec!). I took out a bit out of my metal retort and placed it in a glass test tube that a melted and bent to try to catch the fumes better. As I
applied the heat via blowtorch, what looked like white phosphorus started forming above the reaction and I saw small yellow/orange drops forming
within the reaction mixture. It was about this time I noticed a crack in the glass but I don't know if this was the issue. I continued heating and the
thing literally exploded. It didn't have the characteristic flash of aluminum powder but it definitely could have had some in it. Luckily the glass
was soft from the blowtorch so it didn't shoot fragments as much as it could have. Pretty much my question is, why did it explode? I tested more on
flat rocks and it literally acts like a flash powder that smells like garlic. If I'm going to do this on a bigger scale I'd like to know it won't
explode in a pipe in my face haha. Is there a way to slow the reaction to be more controlled and less, flash powder like? Like I mentioned, my sodium
hexametaphosphate was homemade so I wonder if that could be it. I do have 2 kg of stuff I bought online so I'll test that here soon. Any advice from
anyone more familiar with phosphate reduction? Thanks for any advice in advance 
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Rainwater
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Sounds like a life lesson your lucky to talk about.
A few pointers. Get a notebook and write out all your reaction steps before an experiment. Chemical formulas are hard to do in your head, and the
notebook helps track what/where/when you go wrong.
Keep very detailed notes during an experiment, time stamp every entry, record all the details, compounds, container( especially important),
mass/volume/temp. Make it look like a spreadsheet.
This will aid you greatly in explaining the experiment to others.
Next is safty, small scale to start with. Required cures, Rx, equipment and/or personal if need be.
For example, my first and last time I made P, i didnt know water wouldn't put it out if it cought fire, $u"( me, i distilled it into water, but low
and behold, dam if water didnt make it burn faster and hotter.
Google "Phossy jaw" for more hazard warnings
I would guess that you succeed in making P under oxidizing atmosphere which resulted in ignition that spread to the aluminum powder, that by itself is
pyrophoric
Edit:
Welcome to the forum!
[Edited on 12-5-2024 by Rainwater]
"You can't do that" - challenge accepted
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LesserLordKusanali
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Those are some good pointers and I glad you brought them up. Luckily it was a smaller test batch this time around. As for the formula you mentioned I
got it right here (NaPO3)6 + 10 Al + 3 SiO2 → 3/2 P4 + 5 Al2O3 + 3 Na2SiO3. I wonder if perhaps the small particle size helped it react so fast.
Next time I think I'm going to do what you mentioned and keep careful record of each part of the procedure so it will be easier for more experienced
folk like yourself to give pointers. One thing I do know is the heat applied was almost exactly 1100°C. I'll try a few more unconfined tests with
different reducing agents (zinc. Magnesium, less fine aluminum) and report back. I've heard that even lower temperatures can be used if phosphoric
acid is reduced with carbon or aluminum but I haven't gotten around to trying it yet. The goal is to eventually reach violet phosphorus from various
phosphate fertilizers, it's a fun challenge im trying. When you did it, what method did you use? Did you use glass or metal for the retort? (The
picture is part of the glass retort where the suspected WP fumes touched. After applying more heat they disappeared)
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Rainwater
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I was wanting a sample for my element collection. Match striker plates where distilled in a steel reaction vessel into a container of hot water to
prevent clogging of the narrow tube. It worked as planned until i removed a piece and it caught fire on contact with air. I tossed it backninto the
jar containing all of my sample, and the fire got brighter and more intense, i dumped the entire container into a large bucket of water and was able
to save some moving it away from the fire. If i had to do it again, i would include a welding mask in my equipment list amd work under argon
atmosphere
"You can't do that" - challenge accepted
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BromicAcid
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Particle size comes to mind but the reaction happens at least partially in the liquid phase, sodium hexametaphosphate mp is 628°C, and considering
how glass is made the silicon dioxide probably starts solvating, and just a bit higher (660°C) the aluminum starts to melt as well. I ran almost the
exact same rxn once and it was fairly smooth actually, I was using a metal container with a propane torch and much higher scale, my silicon dioxide
was fumed amorphous silicon so pretty fine. But in that instance the reaction went fine for some time and then I melted a hole in my setup.
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bnull
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Welcome to the forum.
Since you're a (relatively) new member, I recommend you check out the links at the bottom of the page Phosphorus (especially The Wump Incident) and the books on preparative inorganic chemistry in the Library, such as Georg Brauer's Handbook of Preparative Inorganic Chemistry.
Attached below is an example of how to write your experiment notes, taken from Semimicro and Macro Organic Chemistry by Nicholas D. Cheronis,
also available in the Library.
Attachment: Write-up of a typical experiment.pdf (280kB)
This file has been downloaded 91 times
Happy experimenting1!
1: Be careful, use your PPE, don't save on safety, don't rush etc.
Quod scripsi, scripsi.
B. N. Ull
P.S.: Did you know that we have a Library?
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