chloric1
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tricalcium phosphate
I have been preparing tricalcium phosphate for various phosphorus related experiments. The starting materials are Technical Trisodium phosphate and
Damp Rid Calcium Chloride. The working envoronment is outdoors and varies between 30 to 35 degrees Celsius during the day and 17 to 25 celcius at
night. The humidity runs 30 to 100% here. Everything you could expect from Ohio river valley in July.
OK, Now my question. What would cause tricalcium phosphate to precipitate as a jelly? The first time I started with very concentrated solutions and
the jelly look was stable for 24 or more hours. THis time I cut the concentration about in half and the jelly changed to curdly cottage cheese look
after an hour in 33 degree sunshine. Also, it should be noted that the jelly was noticed mostly when TSP was in excess then diminished significantly
as more calcium chloride was added. Lastly, after was the precipitate with 1000 of warm water to remove soluble impurities, I put the paste to dry
on aluminum foil to dry in the sun. after a day or two(depending on humidity) the volume decreases to about 50% original. Is the paste a loose bond
between phosphate and water? Are the phosphates interlocking to make the jelly I observe?
Fellow molecular manipulator
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garage chemist
chemical wizard
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Gel formation is quite common with precipitation of insoluble compounds, for example calcium fluoride, and lots of heavy metal hydroxides.
Try diluting and then boiling your gel for some time, this causes the extremely fine particles (with a stable hydrate layer on them, this is
the cause for the gel formation) to agglomerate into larger particles and precipitate as a powder.
If this doesn't help, don't give up, there are several other methods for breaking gels, I just don't remember them at the moment.
Why don't you try to reduce your trisodium phosphate instead of converting it into calcium phosphate? Sodium phosphates are much easier to
reduce!
[Edited on 4-7-2005 by garage chemist]
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S.C. Wack
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Well, what happens on adding a lot of water to the gel?
This may explain why some here say that CaSO4 in an unfilterable gel, while I find that it and all other Ca salts of low solubility are a joy to
filter even on kg scale, using a kitchen strainer and paper towel. Well, it does retain a lot of solution that has to be removed mechanically, but
still... The difference between a Ca gel and a very easily filtered white solid may only be a volume or three of water.
What happens when dilute solutions of chloride and phosphate are mixed?
Americans above the snow line will find prills of CaCl2 in big heavy bags at WM, to be a very much more economical OTC product. There are also smaller
jugs of the same brand, but look for the bags (in season) as this gives you many many pounds more for only a coupla bucks more.
All of this avoids the question of why, I know.
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chloric1
International Hazard
Posts: 1071
Registered: 8-10-2003
Location: GroupVII of the periodic table
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Mood: Stoichiometrically Balanced
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YesI am aware of the cheaper cost but it is July and hotter than blazes right now. I will try a 1 inch magnetic bar and heat this up. I am a little
worried about bumping but a rapid stir will help. If I can concentrate the product then I will I only rinse the salt once with 500 ml of water
instead of 1000 ml or 1500 ml.
Oh and by the way, I actually want calcium phosphide. I read some patents recently about mixing 85% phosphoric acid with activated charcoal and
drying this mixture at 465 degrees then put in a reaction tube and pass chlorine over at 500 degrees C to get phosphorus oxychloride. I may play with
sodium phosphates also.
By the way, what materials can I sue to fuse phosphate salts? I have Disodium phosphate I want to convert to the pyrophosphate. The local Ace
Hardware sells stainless steel dog bowls. I wonder if the molten phosphates will eat at this too much.
Fellow molecular manipulator
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