| | The Role of Gelatin in Paper Permanency II |
 | | The percent hydroxyproline by weight in mammalian gelatins varies slightly depending on the source of the tissue, the method of manufacture, and the purity of the gelatin; but as an example, a purified calf skin gelatin contains around 14.5% hydroxyproline by weight. |
 | | Following the addition of alkaline copper sulfate and hydrogen peroxide, the mixture of amino acid residues is heated and any hydroxyproline present is converted to a compound called pyrrole which reacts with p-dimethylamino-benzaldehyde in the presence of acid to form a transient magenta-colored compound which is developed by heating. |
 | | Both hydroxyproline and gelatin are moderately stable compounds whose deterioration, under reasonable storage conditions, would become significant only after thousands, not hundreds, of years. |
| aic.stanford.edu /sg/bpg/annual/v13/bp13-02.html (2326 words) |