Sciencemadness Discussion Board

How to measure evaporated water in a reduction

hankxmen - 18-3-2013 at 04:27

Didn't realize i need to distill to measure water evaporated from a reduction using hydrazine hydrate. I am suppose to remove 30 ml but do not have a flask with a side take off. I know i could just evaporate the solution open but i would have no way to be sure how much is evaporated. Is distilling the only way to go? Any other way to measure?

Mailinmypocket - 18-3-2013 at 04:43

Quote: Originally posted by hankxmen  
Didn't realize i need to distill to measure water evaporated from a reduction using hydrazine hydrate. I am suppose to remove 30 ml but do not have a flask with a side take off. I know i could just evaporate the solution open but i would have no way to be sure how much is evaporated. Is distilling the only way to go? Any other way to measure?


You could weigh the flask you are evaporating the water from before and during the process. Pure distilled Water weighs 1g/ml. So remove 30g from your flask and you should be close to your target. If there are other volatiles in there then this obviously won't work and you would need something like a trap to measure the water removed etc. perhaps if you gave us more details on what chemicals are involved?

[Edited on 18-3-2013 by Mailinmypocket]

hankxmen - 18-3-2013 at 04:59

haung minglon modification. wolf kishner reduction (i apologize i did not include that in my first post) the evaporation of the water from the hydrazine hydrate happens after 1 hour of reflux. Nothing explosive but hydrazine is poisonous. So.

Oxygen ruining solution during evaporation?

hankxmen - 18-3-2013 at 11:33

If i need to distill 30 ml of diethylene glycol and koh
and do so without distilling 30 ml and evaporate - will oxygen be absored into my solution and destroy it?:o

[Edited on 18-3-2013 by hankxmen]

zed - 19-3-2013 at 13:15

What is your solvent? Just evaporating may, or may not be an option.

Get better glassware.

ScienceSquirrel - 19-3-2013 at 13:52

In a situation like this it is best to distill off and collect the liquor.
Just boiling it off is asking for trouble.
It might work but it is harder to work out what is happening and you might have fumes from the hydrazine.
At the end of the day, doing it the right way with good equipment is better than trying to wing it.