The new hypothesis based on "heat of a reaction which occurs in both the gas system, and the liquid system should be equal". In the early 19th century, William Henry stated that the concentration of the gas in the "gas system" would be directly proportional to its concentration in the "liquid system" at the constant temperature. However, Henry's law coefficient mainly varies with the temperature of the scheme. Also, Gustav Kirchoff described the "heat capacity", which is equal to change in enthalpy-introduced by Josiah Willard Gibbs in 1870's, then first called "enthalpy" in J. P. Dalton's scientific paper, in 1909-divided by the change in temperature, at constant pressure, in 1858's. This inference is based on the mathematical expression of the single atomic hypothesis. This hypothesis is often derived from a reaction that produces the same product output in two different systems to explain the ongoing events with each other. For example, in order for a coal particle to burn well, it is also important to cause the coal particle to ignite earlier during combustion, which is also an oxidation reaction, due to the oxidation reaction in water.