Henry's Law

Henry's Law is a principle of physics formulated by the English chemist William Henry in 1801. It explains the behavior of gases under pressure: gases become more soluble as pressure increases.

Henry's Law states, specifically, that the concentration of a solute gas in a solution is directly proportional to the partial pressure of that gas above the solution. (p = k'cc where p is the partial pressure of the gas, c is its molar concentration, and k'c is the Henry's law constant on the molar concentration scale.)

Henry's Law explains what happens when divers surface too fast and get decompression sickness ("the bends"). Nitrogen is forced out of the blood as pressure returns to normal, forming bubbles which can cause blockages in blood vessels in the same manner that blood clots do.

Henry's Law also explains why bubbles form in a carbonated beverage when its container is opened. When the liquid is exposed to unpressurized air, the carbon dioxide in it becomes less soluble and is forced out. Shaking the container dissipates the air at the top, forming thousands of micro-sized bubbles. Each bubble offers a tiny surface where CO2 can rapidly come out of solution, creating the potential for explosive fizzing.

The remedy for decompression sickness is a "dive" in a hyperbaric oxygen tank. The increased pressure in the tank simulates a dive of 60-90 feet, at which pressure the nitrogen bubbles are reabsorbed by the body. Oxygen delivered to the cells helps repair damaged tissues. The pressure is very gradually decreased to one atmosphere ("normal" sea-level pressure), simulating the proper slow ascent to the surface. A hyperbaric oxgen tank is a very cool gadget.

Another cool gadget which relies on the principle of Henry's Law is the Cooper Cooler, a “Rapid Beverage Chilling Appliance” recently given a good review by Modern Drunkard Magazine. Warm cans or bottles of beer, wine, or soda can be chilled in this device within a minute or so. The Cooper Cooler works by rotating the container rapidly in an ice-filled chamber. When a beverage is rotated, as opposed to shaken, the air pocket basically stays intact. Decarbonation can therefore only take place at at the surface.

Medical researchers are finding new applications for hyperbaric oxgen chambers all the time. And modern drunkards are apparently working just as hard putting their knowledge of physics to work so they can stash beer in the closet, away from greedy roommates, and render it palatably chilled in 60 seconds flat. Isn't science wonderful?