The basic strength of the methylated guanidines [and] Studies in dilution in the rumen of the sheep

The work described in this thesis falls into two independent parts. Part 1 is pure chemistry. It describes the systematic preparation of the eight isomeric and homologous methylguanidines in the form of stable, water-soluble derivatives and the determination of their basic dissociation-constants. The basic strength of the parent compound, guanidine, is re—investigated and the constants found for the nine compounds are compared and discussed in terms of resonance energy. The experimental results are compared with certain predictions made by Pauling. Part 2 is biomedical. It describes the search for a substance which can be introduced into the rumen of the sheep and recovered unchanged at intervals of time for estimation; so that the process of dilution and loss through the omasum can be followed. These estimations will enable the digestion-studies of other workers to be placed on a quantitative basis. The material chosen is polyvinyl alcohol, and a colorimetric method of estimation suggested by earlier workers is developed for use in aqueous solution, and finally adapted to rumen-liquor