The optical rotation of gelatin films

Optical rotation measurements of a series of relatively thick gelatin films prepared under a variety of drying conditions were made. The technique permits rotation measurements to be made during the drying process. It is found that the temperature and humidity of the drying air do not significantly affect the rotation of the films at temperatures below about 25°C. wet bulb. Above this temperature the rotation drops sharply. Films containing formaldehyde and mucochloric acid as hardeners tend to have lower rotations than unhardened films. Various types of gelatin show differences in the gel state, but not when dried. The results of these experiments indicate that in general gelatin tends to acquire the same level of ordered structure during drying, regardless of the drying conditions and type of gelatin. This tendency is inhibited only by high temperatures or the establishment of stable intermolecular crosslinks by hardeners.