Chemguy Posted October 13, 2006 Posted October 13, 2006 In another topic by me, you may have noticed that I made an unsuccesful gunpowder using K2CrO7, now I have decided to use the Cr2O from this. Now the Cr2O3 is suprisingly pure, as it was made through gunpowder, I put the green powder, clumps that formed into a water bath and left it for a few days to get rid of some/any of the soluable impuries, then I evapotated the water, now it is a dull, fine green powder. I have about 10 grams. But this isn't very usefull in it's current state, so I read up about chromium trioxide CrO3, on wikipedia and some other sites, it is a powerfull oxidizer and I wan't to make a small amount. So after unsuccesful searches on google and this site, here is my question.Is it possible to make CrO3 from Cr2O3, I have tried heating with KNO3 in the hopes that it might oxidize it, it obviously didn't work, so does anyone else know anything about this?
Swany Posted October 14, 2006 Posted October 14, 2006 How are you sure of its purity? I may suggest a washing or two with some strong HCl, as the Cr2O3 is fairly resistant to attack by this. Oxidation... humm. I suppose one could try conc. H2O2, Perhaps permagnate solution, I am not sure of the oxidiser heirarchy off the top of my head. Another option would be to dissolve it in HCl, and attempt to oxidise a solution which may ppt. the CrO3 salt. Electrolysis may then be plausible. Have fun.
Chemguy Posted October 14, 2006 Author Posted October 14, 2006 I will try Permanganate, if that doesn't work I will try electrolysis. I know it isn't anything like 100%, but it is a dark dull green powder, i'd say about 90% - 95%. Also when I put it in water and filter it there is the same amount. Although it could just be another insoluable salt. Thanks for ther help, I will have fun.
Ramiel Posted October 15, 2006 Posted October 15, 2006 Also high-oxidation Cromium compounds are carcinogenic/teratogenic. God's sake, don't get it on your skin/clothes/tools!
Mumbles Posted October 15, 2006 Posted October 15, 2006 I do believe high conc H2O2 action on Cr2O3 will be able to oxidise it to CrO3, acidified perhaps. Heat decomposed ammonium dichromate by the following mechanism: (NH4)2Cr2O7 ---> N2 + 4 H2O + Cr2O3 I don't think the same goes for potassium or sodium salts. Heat could give CrO3, but if the temp required is more than 250C, the CrO3 will decompose to Cr2O3. Nice to see you around Ramiel. It's been a while since I've gotten a good look over at SMDB.
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