After completely dried in an oven, several kinds of fishmeal (Table 1) were exposed into five humidors at several constant humidities and at an constant temperature (20°C.), and wetted to saturation. The increment of weight was measured. Thus, the hygroscopicity was calculated (Table 2), with the results as follows:- (1) Over the range of 1-0•49 of relative humidity R (in ordinal fraction) the relation between the moisture absorbed per unit mass of the dry matter WR and R is empirically formulated as
(W1-WR)n=k(1-R),
where n and k are constants (Fig. 1, Table 2).
(2) The value of WR has a negative correlation with the fat content of the material, and as the humidity decreases the correlation becomes less close.
Seeing that the transfer of moisture in the pile of fish meal obeys the ordinary law of diffusion, the author determined the coefficient of diffusivity K by measuring the distribution of moisture in the fishmeal, which was filled in a glass tube with an open end and kept in a constant humidity, R=0•9, for 1-3 days. The results obtained are summarized in Table 3 from which we can see that the value of K has a negative correlation with the apparent density of the material. This fact leads to the conclusion that the migration of moisture takes place in the space among the particles of fishmeal.