Scuba divers [local] must be very conscious of Caisson's disease, commonly called 'The Bends'.
The Bends is a nitrogen solubility problem. Since the air we breathe is 78% nitrogen, nitrogen is dissolved in all of our tissues. The amount of nitrogen dissolved is related to atmospheric pressure.
Henry's law describes the amount of dissolved nitrogen. Henry's law states that the solubility of a gas in a liquid is proportional to the pressure of the gas over the solution. Nitrogen is 78% of the standard atmosphere. Nitrogen's partial pressure then at sea level is 78 % of 1 atmosphere, or 0.78 atmospheres. The solubility of nitrogen at sea level and 25¡C can be determined using Henry's Law:
At standard conditions, there are 0.000488 moles of nitrogen dissolved in every liter of blood. Doesn't sound like a large amount, you say? Well if that quantity were converted to a gas at those conditions, they would occupy 15 mL for every L of blood.
As the pressure of the atmosphere increases, so does the solubility of all gases. Since nitrogen is found in such a large concentration in our atmosphere, it presents a problem.
As scuba divers dive to deeper depths, the pressure of air they breathe must match the pressure of the water around them. This increase in air pressure increases the solubility of nitrogen according to Le Chatelier's Principle.
Nitrogen is essentially chemically inert; it does not react easily. The increased nitrogen solubility is not a chemical problem but a physical problem. If the high pressure making nitrogen dissolve is rapidly lowered or removed, the nitrogen becomes insoluble and returns to its gaseous state-as gas bubbles. These gas bubbles are trapped in the tissues and blood stream in a process called 'aeroembolism'. The bubbles can be transported to vital tissues such as your brain where they cause serious problems. Understanding nitrogen and its solubility are key to making sense of the phenomenon known as 'the Bends'.
