Note 57 — Chapter IX · THE PHYSICAL CHEMISTRY OF THE HIDE-FIBRE.

The acid retained by the gelatine, as measured by deducting from the total contained in the jelly, a quantity equivalent to the volume of solution absorbed, at first rises rapidly to a maximum, then slightly diminishes and remains practically constant. On the theory suggested, it is evident, however, that the absorbed solution must be more dilute than that outside, and the actual combined acid greater than that shown by the above calculation. The “combined” acid, as determined by indicators, shows slight but continuous increase. It is acid to phenolphthalein, but neutral to methyl orange.