Henry’s law

Liquid steel, and to a reasonable extent hot metal primarily fall in the category of dilute solution. In a dilute binary solution activity of a solute obeys Henry’s law, which is stated as

(8)

where  is a constant (activity coefficient for the solute in dilute binary) and is the mole fraction of the specie i. Solutes in all infinite dilute solutions obey Henry’s law. Deviation from Henry’s law occurs when the solute concentration increases.

In steelmaking the concentration of solute in molten steel is expressed in weight percent. It is frequently most convenient to choose the infinitely dilute solution expressed in terms of weight percent as the standard state. This is defined as

(9)

For weight percent i other than zero

(10)