III.8.5. Note on the dry ice and the liquid nitrogen:
III.8.5.1. Effects of smoke:
Dry ice is one from the most extraordinary known sources of cold. Each kilogram frees 150
frigories (655 kJ). It frees cold three times more than the same volume of water ice, and at a much lower
The temperature of dry ice is -80°C and becomes carbon dioxide. The dry ice is usually and
widely used for the transport, in laboratories and in food industries. The dry ice is often recommended for
the respect for the cold chain.
III.8.5.2. Precautions of use:
· Use gloves and glasses during its manipulation. Do not swallow; risks of burning.
· Do not carry more than 20 kg of dry ice in a car, risk of asphyxiation with the dioxide of carbon.
· Do not put some dry ice in a hermetic bowl, risk of explosion.
· Do not store the dry ice in a confined room.
· Keep out of reach of children.
The same properties are obtained with some liquid nitrogen, another substance which produces
some "smoke". The liquid nitrogen (-176°C) is even more dangerous to manipulate (the companyAir
Liquid disadvises to use it in a gourmet restaurant by concerns of security). The contact with this product
can cause burns and can, in high dose, provoke risks of asphyxiation. The same rules of security have to
III.8.5.3. Two theories on the smoke formation:
· In practice, dry ice looses some carbon dioxide when it warms up. The carbon dioxide is a gas denser
than the air; it goes down, compared to the steam and is more visible.
· The very cold gas can cool the ambient air. The water vapour in air can condense and make a natural
smoke (similar to a cloud), denser than the air.
III.8.6. Test with some dry ice and liquid nitrogen:
III.8.6.1. Material :
· 400 ml of reduced «fond blanc» in half.
· 2 soft-boiled eggs.
· 100 ml of liquid cream.
· 1 spoon of vinegar.
· 1 red sweet pepper.
· Salt and pepper.
III.8.6.2. Method :
The method is identical to the former recipe. The ice cube is however an ice cube of dry ice. In
the test in the liquid nitrogen, we pour liquid nitrogen after having poured our warm liquid in the glass, to