Hydrogenation of western hemlock tannin extracts.

Unpurified Western Hemlock bark tannin extracts were hydrogenated in the presence and absence of alkali, using Raney nickel as a catalyst. The effect of time, temperature, alkali concentration and catalyst was studied by determining the total amount of phenolic substances (ether solubles) and the relative amounts of phenols and phenolic acids. High yields of phenolic compounds, based on the tannin content of the extract were obtained using relatively mild degradation conditions and the presence of alkali was not necessary to obtain these high yields. Catechol and protocatechuic acid were identified by paper chromatography but other substances apparently are also present. The reaction is complex in nature and needs further study especially with respect to the identification of other main products. A mechanism is suggested which explains the results obtained under differing conditions.Applied Science, Faculty ofChemical and Biological Engineering, Department ofGraduat