Le 06/09/2011 12:08, Invisible a écrit :
> 
> Unrelated, but I note that dissolving ammonia in water is an endothermic
> reaction. That, apparently, is how Victorian icecream was made. So I
> guess the question is, WOULD YOU EAT IT? ;-)

Hydration of common salt is endothermic. The fusion temperature of the
mix is usually lower than the fusion of clear water.
(For road usage: Hydration of CaCl2 is exothermic, but the one of NaCl
is endothermic; CaCl2 is used in countries with very low temperatures on
their road)

For the preparation of ice-cream (well, rather sorbet (water-based
ice-cream, using fruit juice, water), than the rich ice-cream with cream
of milk, eggs and other stuff), you only have to cool the recipient and
the preparation a bit below 0°C (which can take a lot, as freezing water
has a lot of joules to expel): using a recipient with an internal
container and an external container, you prepare the sorbet in the
internal container, and have the water+ammoniac mixed in the external
container.

(If you remember your chemistry about mixing acid and water (you drop
one in the other, but avoid the other way round), can you guess what
must be added to what (ammoniac is a base)) ?

Nothing related to the fancy preparation of ice-cream with liquid
Nitrogen (pour liquid nitrogen over the preparation, and mix with energy
and a wood spatula (and some goggles, and some heavy gloves)!).

I would be interested in a preparation with liquid Oxygen, served at a
table of smoking people... well, soon-ex-people. I'm just afraid the
reaction with liquid Oxygen would also change the taste too much.
(oxidation power is very strong)

-- 
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and you can't drill a hole in it and stick a rivet into it doesn't mean
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