Henry’s Law describes the ratio between two gas concentrations:
1. The concentration of a specific gas (e.g., CO2) dissolved in a liquid phase, (e.g., ocean water)
versus
2. The concentration of the same gas in the gas phase which is in continuous contact with the liquid phase (e.g. CO2 in air above ocean water).
- where the ratio changes based on temperature of the surface interface between the gas and liquid phases
- where the ratio does not change based on the amount of the gas present,
- where the ratio changes based on the identities of the gas and the liquid.
A Henry’s Law constant is a ratio which describes the net amount of a gas in atmosphere versus that same gas in ocean water in contact with the atmosphere. But more generally, it describes all gases in contact with all liquids. Henry’s Law is not a human invention, hypothesis or theory, but rather carefully documented observations of nature. The primary gases in the atmosphere are nitrogen (78.084%,) oxygen (20.947%,) and argon (0.934%,) in the driest of conditions. However, water vapor (H2O) can compose as much as 4% of the atmosphere in damp conditions and is highly variable.
The total of all other gases make up less than 1% of atmosphere and are called trace gases. These trace gases include carbon dioxide, ozone, methane, various oxides of nitrogen, neon, helium, hydrogen and other rare gases. They are called trace gases because they exist in small amounts. For example, the combined sum of natural and human-produced carbon dioxide is only 0.04% to 0.05% of the total atmospheric gases.
Carbon dioxide (CO2) is both produced and used by many natural and human processes. Plants, animals, and inorganic chemical reactions use CO2 from air, water, soil and rock and also return CO2 in various chemical forms to the environment as bones and cellular structures of living creatures, then later in deposits such as shells, corals, and sedimentary rocks. The net result is CO2 gas is being continuously removed from the environment for thousands or millions of years, and replaced by burning fossil fuels, cement production, respiration, volcanoes and tectonics, and these enormous processes are continuously mediated by Henry’s Law and chemical balancing of the giant dissolved carbon reservoir in the ocean and CO2 emitted.
The amount of CO2 man introduces into the atmosphere by the combustion of carbon-based fuels is inconsequential, easily absorbed by the environment. Man could reduce his use of hydrocarbon fuels by 100% or increase them by 500% and at the end of the day 0% change in net atmospheric CO2 concentration will be the result. This natural result occurs because any increase in any atmospheric gas concentration is offset by a proportional increase in absorption of that gas into nearby liquids. If CO2 increases by 100% in a local area, then 100% more CO2 will be dissolved into water in the local area. If CO2 emission doubles, then water which is in contact with that CO2 absorbs that increase and returns the CO2 concentration to the CO2 water/air ratio for the local temperature, and this is true for all gases not only CO2. For all gases, colder water absorbs more gas, warmer water emits more gas. Oxygen which is dissolved in water and absorbed by fish gills for their respiration, the CO2 which is the necessary gas of life for all green plants and thus all life, as well as the oxygen which is exchanged with CO2 in the lungs of animals and humans, each of these vital natural processes rely on Henry’s Law.
Henry’s Law is a fundamental law of physical chemistry which naturally regulates and controls the Earth’s atmospheric content of CO2. This counteracts any net CO2 increases in the atmosphere caused by the worldwide combustion of hydrocarbon fuel sources.