mabuse_ - 1-6-2012 at 09:59
I'm lacking some basic knowledge here, maybe you can help me a little:
I wonder what will attack magnesium most:
#Pure water
#Pure ethanol
#Or pure isopropanol?
It's about solvents used in Pyrotechnics and working with alcohol soluble binders.
Acetone shall not be discussed here.
Alcohol is often said to be more friendly towards Mg than water. If we assume it's waterfree, it wont't dissolve any nitrates present.
But it will still attack the Mg by forming Mg-alkoxid.
I wonder what will hurt more in this respect - isopropanol or ethanol?
[Edited on 1-6-2012 by mabuse_]
[Edited on 1-6-2012 by mabuse_]
Endimion17 - 1-6-2012 at 10:48
I hope you know magnesium doesn't react appreciately with cold water.
I doubt it will step into a reaction with any alcohol ar room temperature. Consider the pK<sub>a</sub> of each:
methanol 15.5
water 15.74
ethanol 15.9
isopropanol 16.5
The higher the number, the weaker the acid, of course.
Nicodem - 1-6-2012 at 10:59
Magnesium reacts with dry lower alcohols. The reaction does not start easily though, due to the surface protection of the metal, but once it starts it
goes on quite exothermically. I would assume that with magnesium powder it could go rapidly as well. Due to the need for the surface layer etching, it
is unpredictable. It will likely not start under normal conditions in most cases.
AJKOER - 1-6-2012 at 13:34
Apparently, it is a known fact that a small amount of iodine or carbon disulphide can induce the reaction between methyl alcohol and magnesium.
See, for example, comment at:
http://pubs.acs.org/doi/abs/10.1021/ja01972a014
mabuse_ - 6-6-2012 at 13:18
Thank you for your answers.
Well the question is, what will happen if there is some nitrate present. To a very little extent they will be dissolved in alcohol.
But isopropanol seems to be superior to ethanol, or at least not worse. Given the fact that commercial ethanol contains water and ethanol is available
in 99% purity it seems to be the better choice.
Hexavalent - 6-6-2012 at 13:33
Nicodem - is that forming the alcoxide? For example, magnesium reacting with EtOH to generate magnesium ethoxide, with iPrOH to generate magnesium
isopropoxide etc.?
[Edited on 6-6-2012 by Hexavalent]