Tim_Lou Posted December 8, 2004 Report Share Posted December 8, 2004 my latin teacher told me that in acient Roman, people use urea as a purifying dye.they use them to dye the color white. thats pretty disgusting... well, as people heat urea, they get ammonium, thats how it is able to dye white.NH2--CO--NH2 --> NH4CNO Quote Link to comment Share on other sites More sharing options...
TINNY Posted December 9, 2004 Report Share Posted December 9, 2004 what's the relation of ammonia with ability to dye white? Quote Link to comment Share on other sites More sharing options...
Tormod Posted December 9, 2004 Report Share Posted December 9, 2004 what's the relation of ammonia with ability to dye white? Yeah...doesn't ammonia simply remove colors? Quote Link to comment Share on other sites More sharing options...
Tim_Lou Posted December 9, 2004 Author Report Share Posted December 9, 2004 well, its not really dye white... but remove colors on the wools so that it appears white.(all Roman clothes are made out of wools... well, maybe silk, but its only for very rich peopple) Quote Link to comment Share on other sites More sharing options...
TINNY Posted December 10, 2004 Report Share Posted December 10, 2004 so you've tested it? Quote Link to comment Share on other sites More sharing options...
Tim_Lou Posted December 11, 2004 Author Report Share Posted December 11, 2004 lol... i can just buy bleacher in store, no need to use urea ;) . Quote Link to comment Share on other sites More sharing options...
TINNY Posted December 12, 2004 Report Share Posted December 12, 2004 of course. but i thought you should verify the accuracy it just for the sake of it. You obviously don't want to put your urea to practical use! Quote Link to comment Share on other sites More sharing options...
Tim_Lou Posted December 12, 2004 Author Report Share Posted December 12, 2004 well, i cant do this experiment, but i find something on the internet: http://www.uni-regensburg.de/Fakultaeten/nat_Fak_IV/Organische_Chemie/Didaktik/Keusch/D-Urease-e.htm take a look at the chemical equation at the nearly bottom. (er, cant find an online demo) ;) Quote Link to comment Share on other sites More sharing options...
TINNY Posted December 13, 2004 Report Share Posted December 13, 2004 oh.... so you need the urease enzyme. i thought you just produce your own urea onto the cloth that you want to dye.No wonder I thought it strange that water and urea can so easily produce ammonia... Quote Link to comment Share on other sites More sharing options...
Tim_Lou Posted December 13, 2004 Author Report Share Posted December 13, 2004 edit: urease enzyme is required in the decomposition of urea in soil, but in the case of boiling it, it is not necessary to have enzyme. Quote Link to comment Share on other sites More sharing options...
TINNY Posted December 14, 2004 Report Share Posted December 14, 2004 so you can't just pee on your clothes and turn it colorless Quote Link to comment Share on other sites More sharing options...
Tim_Lou Posted December 14, 2004 Author Report Share Posted December 14, 2004 lol....i dont think so....well, you can heat it... ;) Quote Link to comment Share on other sites More sharing options...
TINNY Posted December 16, 2004 Report Share Posted December 16, 2004 so 37 degrees C is not warm enough huh? Quote Link to comment Share on other sites More sharing options...
Tim_Lou Posted December 17, 2004 Author Report Share Posted December 17, 2004 its an equilibrium problem, 37 degrees might not have a good yield of ammonia...anyway, after many more research, i figured out that when urea is heated, the reation should be:CO(NH2)2 --> NH4NCO, the reverse of Wöhler's famous synthesis of urea. (1st time of converting inorganic compounds to organic compounds), where NH4- ion converts to NH3 and escape, leaving the dangerous NCO- (cyanate) ion..."In an open system, half the urea was destroyed after 5 hr @ 90 o C and pH 7, Half life estimated 25 years @ 25 o C "from http://carewinnipeg.com/OriginofLifeStudies.htm...in order to calculate the yield under certain temperature, or the reaction rate, an equilibrium constant or reaction rate constant in certain temperature is needed..... which i cant find them anywhere, sorry about that... :) Quote Link to comment Share on other sites More sharing options...
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