Henry’s Law

Henry’s Law is named for William Henry, who in 1801 stated that the mass of a gas which dissolves in a volume of liquid is proportional to the pressure of the gas.

e^P = e^{kC}

Taking the natural logarithm of this equation we get the more common version:


Where P = the partial pressure of the gas solute, 
C is the concentration of the gas 
and K = the Henry’s Law constant.

To a scuba diver Henry’s Law tells us that at higher pressure our bodies will absorb more gasses. At great depths, the amount of nitrogen (and other gases) absorbed into our blood and tissue is greater than the amount absorbed at shallow depths. That is why a diver going to 100′ has a greater risk of decompression illness than a diver who dives only 30 feet. Since the shallow diver has absorbed less gas, it is less likely to come out of solution in the body.