This value of B corresponds to I =1640, the saturation point for soft iron.
According to Joule's observations, the length of a bar of iron or soft steel was increased by magnetization, the elongation being proportional up to a certain point to the square of the intensity of magnetization; but when the " saturation point " was approached the elongation was less than this law would require, and a stage was finally reached at which further increase of the magnetizing force produced little or no effect upon the length.
If, however, a solution be cooled slowly past its saturation point with no solid present, crystallization does not occur till some lower temperature is reached.
Between the saturation point and this lower temperature, the liquid holds in solution more of the solute than corresponds with equilibrium, and is said to be supersaturated.
A familiar example is to be found in solutions of sodium sulphate, which may be cooled much below their saturation point and kept in the liquid state till a crystal of the hydrate Na 2 SO 4 IoH 2 O is dropped in, when solidification occurs with a large evolution of latent heat.
