cyanureeves
National Hazard
Posts: 744
Registered: 29-8-2010
Location: Mars
Member Is Offline
Mood: No Mood
|
|
salts or crystals
gentlemen how do i get my cystals to dry?i got chromium trioxide forming at the bottom a flask but when i decant the excess liquid(sulfuric acid)more
liquid is produced by the crystals left in the flask and more crystals are produced by the decanted sulfuric acid mixture. as of now i just added more
sodium dichromate since it appears that the liquid is more wanting.
|
|
|
not_important
International Hazard
Posts: 3873
Registered: 21-7-2006
Member Is Offline
Mood: No Mood
|
|
Chromium trioxide is hygroscopic - it absorbs water from the air. The instructions for its preparation tell you to wash the CrO3 crystals with
concentrated nitric acid to remove the H2SO4 and Na/K salts, then dry in a desiccator.
|
|
|
cyanureeves
National Hazard
Posts: 744
Registered: 29-8-2010
Location: Mars
Member Is Offline
Mood: No Mood
|
|
hey .thanks. i just went by wikipedia. some of the crystals are holding pretty good. i will put nitric on those.i left them outside last night and
they were drying during the day but this morning it was kind of cloudy so they must've took in some water. by the way where did you see those
instructions?
|
|
|
not_important
International Hazard
Posts: 3873
Registered: 21-7-2006
Member Is Offline
Mood: No Mood
|
|
Do a search at the Internet Archives for "inorganic chemistry" and check those that are 'preparative' or 'laboratory' type books. I'm just remembering
from doing this decades ago, using books such as those you'll find.
You can't dry CrO3 in the air, it will pick up whatever moisture is in the air. Once you've washed it and (quickly) drained off the wash you must
protect the crystals from contact with ordinary air. One common suggestion, after the HNO3 wash, is to dry them in a desiccator over NaOH or KOH
pellets, which absorb both water and HNO3.
|
|
|
![[*]](images/xpblue/default_icon.gif){kind=icon}
