As much as three-quarters of the nitrogen in some Paleozoic shales was released as ammonia by acid hydrolysis; from 1 to 5 per cent as amino acids. The nitrogen released as ammonia occurred largely as ammonium ions held within the octahedral pores making up the crystalline nuclei of illite clay minerals. The presence of nitrogenous organic constituents within the characteristic expansible layers of silicate minerals was also indicated. The organic matter adsorbed on the internal surfaces of the clay was non-extractable with alkali, but was removed readily through decomposition of the clay with hydrofluoric acid.

A comparison of the organic constituents in shales with those in recent sediments showed that a smaller fraction of the organic matter in shales occurred in protein derivatives. The carbon-organic nitrogen ratio in shales was higher than in recent deposits. The suggestion is made that the transformation of complex organic materials in marine muds consists, in part, of the formation of aromatic compounds from sugar-amine condensation products, and that, concomitantly, nitrogen is lost as ammonia and petroleum constituents are formed.

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