Sciencemadness Discussion Board

phosphine generation from baking powder

BauArf56 - 18-4-2021 at 05:10

Once i mixed magnesium turnings with baking powder (which is disodium diphosphate and sodium carbonate) in a 1:1 mixture for making some phosphorus. Wrapped the mixture in some very tight aluminum foil (the best way for heating it without any air) and heated it to red hot for about 2 minutes. I opened the foil and the powder inside was black. When i placed it in water it started bubbling quite strongly and gave off a stinky gas. I thought that reaction produced some magnesium phosphide (i obtained the same phosphide powder by heating some red p with mg shavings). How good is this method? :)

BauArf56 - 19-4-2021 at 06:12

edit: the gas given is flammable and burns with the typical greenish flame of phosphorus. Wiki says that it can self ignite, but mine is not pyrophoric. Says also that ignition is caused by diphosphane formation which should give to the gas that smell. So phosphine smells but it's not pyrophoric. Any ideas?

TheMrbunGee - 19-4-2021 at 06:19

Seems more like You made sodium metal, Black color might be carbon from Mg+CO2. Gas might be hydrogen in this case, and smell from side reactions.

Does burning of gas produce white smoke?

BauArf56 - 19-4-2021 at 06:26

Quote: Originally posted by TheMrbunGee  
Seems more like You made sodium metal, Black color might be carbon from Mg+CO2. Gas might be hydrogen in this case, and smell from side reactions.

Does burning of gas produce white smoke?


yeah, i thought about sodium too, but what makes me thinking about ph3 is that it has exactly the same smell as magnesium phosphide from mg/p reaction. I didn't noticed white smoke from combustion but, as i said, the flame color is as greenish as burning red p. Maybe a mixture of mg3p2 and na?

woelen - 19-4-2021 at 09:44

I think that your product is (very impure) Mg3P2. Magnesium certainly can reduce phosphate to phosphide. There also will be MgO in the mix, and maybe even some MgH2. Of course there will also be Na-phosphates in the mix. The product then produces a mix of H2 and PH3 when water is added. I also can imagine that the reduction produces some carbon and maybe some magnesium carbide.

[Edited on 19-4-21 by woelen]

unionised - 19-4-2021 at 09:51

Some of the aluminium may also have reacted.

BauArf56 - 20-4-2021 at 00:18

thank you all for answering. I think that it's quite hard that magnesium carbide has formed, as Brauer says that MgC2 decomposes below 500 C (see page 920). Magnesium hydride decomposes at 287 C, so very small amount might be formed. Probably some aluminum has reacted at a such temperature. So the gas formed should be PH3 + H2, so i think that it could be used for experiments with phosphine, as h2 is almost inert.

FragranceLover89 - 29-4-2021 at 16:04

Did it smell more like sulfur or ammonia?

[Edited on 30-4-2021 by FragranceLover89]

[Edited on 30-4-2021 by FragranceLover89]

BauArf56 - 23-5-2021 at 04:38

Quote: Originally posted by FragranceLover89  
Did it smell more like sulfur or ammonia?

[Edited on 30-4-2021 by FragranceLover89]

[Edited on 30-4-2021 by FragranceLover89]


hmmm... it wasn't as strong as ammonia, so more likely sulfur. Actually it smells like garlic. Why this question?

symboom - 23-5-2021 at 06:13

"A typical formulation (by weight) could call for 30% sodium bicarbonate, 5–12% monocalcium phosphate, and 21–26% sodium aluminium sulfate. Alternately, a commercial baking powder might use sodium acid pyrophosphate as one of the two acidic components instead of sodium aluminium sulfate. Another typical acid in such formulations is cream of tartar (KC4H5O6), a derivative of tartaric acid.In some jurisdictions, it is required that baking soda must produce at least 10 per cent of its weight of carbon dioxide."

Source: wikipedia - baking power



[Edited on 23-5-2021 by symboom]

[Edited on 23-5-2021 by symboom]

Texium - 23-5-2021 at 06:47

Quote: Originally posted by symboom  
A typical formulation (by weight) could call for 30% sodium bicarbonate, 5–12% monocalcium phosphate, and 21–26% sodium aluminium sulfate. Alternately, a commercial baking powder might use sodium acid pyrophosphate as one of the two acidic components instead of sodium aluminium sulfate. Another typical acid in such formulations is cream of tartar (KC4H5O6), a derivative of tartaric acid.[6] In some jurisdictions, it is required that baking soda must produce at least 10 per cent of its weight of carbon dioxide.
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