yellowbutthole - 18-9-2013 at 12:16
I ordered a sample of 2,4-dinitrophenol sodium salt. I think DNP is supposed to be yellow as the salt and as not a salt right?
I dissolved the yellow dnp sodium into water and dripped it into concentrated hcl. The yellow solution disappeared into a white cloud that quickly
faded. After it was all added the salt started to crystallize out as an off white crystal with a slight yellow tint.
Why did it get white? Can this really be 2,4-dnp or something else?
[Edited on 18-9-2013 by yellowbutthole]
DraconicAcid - 18-9-2013 at 12:38
A lot of phenols are colourless crystals or white powder when perfectly pure, but more usually slightly coloured due to impurities resulting from
oxidation by air. That being said, I wouldn't be at all surprised if the dinitrophenol was not white; dinitroaniline (very similar structure) is
strongly orange.
Lessee...Merck Index says it's yellowish to yellow crystals. Acts as an indicator- yellow in neutral or basic solution, colourless at pH = 2.6.
yellowbutthole - 18-9-2013 at 12:56
ok thats a relief thanks a lot. im going to upload pictures.
yellowbutthole - 18-9-2013 at 13:21
Here are the pics
1 the original sample
2 the crystals after removal of the sodium with hcl
3 the cloudy mixture of crystals in water (with residual sodium salt because i forgot to wash it)
4 the solution has no more crystals except for sodium hydroxide crystals
5 after evaporating the water there is yellow solid
[Edited on 18-9-2013 by yellowbutthole]
Boffis - 18-9-2013 at 14:42
If you recrystallize 2,4 dinitrophenol from 28% HCl it crystallises and colourless platy crystals. If you use boiling water or alcohol water mixtures
it crystallises as yellow crystals but not as intensely coloured as the sodium salt.