Abstract: In present paper the effect of addition of potassium thiocyanate, ammonium thiocyanace, thiourea and urea on the infra-red absorbance intensity and the peak shift of photographic gelatin is investigated. The experiment results show that with the increase of above-mentioned additives the deformation vibration peak intensity of the N-H bond at the wave-number of 1550 cm^-1 is weakened, but the peak intensity at 1536 cm^-1 is enhanced. The more the additives is added, the stronger the peak intensity at 1536 cm^-1. The peak shift from wave-number 1550 cm^-1 to 1536 cm^-1 is a gradual transition process. When the additive amount exceeds definite value the peak intensity at 1536 cm^-1 prevails. All the experimental results elucidate the destroying effect of these additives on the renaturation ability of the gelatin macromolecule in forming the multiple structure.

Key words: Gelatin, renaturation, potassium thiocyanate, thiourea