Bounty_ - 12-1-2007 at 17:23
Hi, I'm looking for a salt to be liquid from about 90°C to around 1150°C
and to be not toxic if lost in the environment.
I thought of NaNO3 or KNO3 but between 380°C and 400°C
they both decomposes.
I have found NaOH melts at 318°C and boils at 1390°C but
has a too high melting point and obviously is not environmental
friendly. 
Any other idea?
Thankyou verymuch in advance
[Modificato il 13-1-2007 da Bounty_]
encipher - 12-1-2007 at 17:49
Due to the structure of the crystal lattice of most ionic compounds, (in which each charged species is surrounded by species of opposite charge),
which gives the compound a great deal of stability, most ionic compounds have relatively high melting points.
However, there does exist room-temperature ionic liquids. I don't know much about them. Wikipedia does have an article about RTIL's though:
http://en.wikipedia.org/wiki/Ionic_liquid
Ozone - 12-1-2007 at 19:30
A typical ionic liquid is 1-methyl-3-ethylimidazolyl tetrachloroaluminate (or, methanesulphonate, thiocyanate, etc.). These materials are eutectic
salts melting below 100°C. Unfortunately (or quite fortunately, as the case may be), some of these materials can be distilled under vacuum (despite
very low vapor pressure) at temperatures ~ 300°C. I am fairly sure that temperatures exceeding this (by much) would lead to decomposition.
For the upper temperature limit of 1150°C, you sould need an inorganic eutectic composition. I'll see whatI can find in the "Molten Salt Chemistry"
ACS series I recently aquired
. In the meanwhile, a more thorough internet search
is in order!
That is one hell of a temperature range you are looking for though (this puts us into "quasi" areas of both organic and inorganic salt mixtures).
Oh yes, if you want to heat up an organic ionic liquid very quickly, us the microwave! Just watch out for superheating and remember, if the stuff is
boiling, the temperature of the material may exceed 300°C! This can happen in seconds.
Cheers,
O3
matei - 13-1-2007 at 03:43
I've just posted a book called "Ionic Liquids in Synthesis" on the New Books (Organic Chemistry) thread. Hope you'll find there the answers you need.
Ozone - 13-1-2007 at 08:15
Thanks matei! I have the whole ACS monograph series, but have not been bale to find reference to a eutectic operable within the desired range.
Cool,
O3
Bounty_ - 13-1-2007 at 16:23
Thanks for the help looking for "ionic liquid" in wikipedia brought me to look for:
"molten salts" in wikipedia.
Perhaps I have found another candidate:
Sodium tetrachloroaluminate NaAlCl4 melting point of approximately 160°C
found in http://en.wikipedia.org/wiki/Molten_salt_battery
but, which is the boiling point?