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N-Dephenylation of N-phenyl-2-naphthylamine (PBNA) is strictly limited in dogs, and a 5 mg/kg dose gives 0-10 microng of urinary 2-naphthylamine (BNA), which does not appear to undergo further metabolism. Neither 2-naphthylhydroxylamine (BNHA) nor 2-amino-1-naphthylsulphate were detected in the urine of treated animals. Urinary output of BNA varies markedly between dogs, and at different times in the same animal. The extent of PBNA N-dephenylation is unaltered by chronic administration. Calculations based on Druckery and Küpfmüller's equation (1948) and present data indicate that, for dogs to form BNA tumours through exposure to a relatively high dose-level of PBNA, the period of daily dosing would occupy, or even exceed, the normal life-span. The carcinogenic risk of PBNA to human subjects is discussed.

CHROMATOGRAPHIC and spectrophotometric properties of ellagic acid have now been investigated in order to facilitate the identification of this acid in plant extracts and hydrolysates. In early studies, ellagic acid has not always been adequately characterized; but the present work has confirmed the occurrence of this substance in a wide range of dicotyledonous plants1. Ellagic acid has also been identified in Terminalia arjuna, bellirica, citrina, pallida and travencoriensis for the first time.

An exploratory study of those reactions of catechin which lead to polymer formation has enabled the conditions for autoxidation to be defined. The formation of polymers and hydrogen peroxide during the autoxidation at 35 and pH6-8 of catechin and of related 3': 4'-dihydroxyflavans has been studied by measurement of oxygen uptake, and by absorption spectra, colour reactions and chromatographic properties of the polymers, and by elementary analyses of the electrodialysed polymers (1). The evidence obtained together with that provided by spectroscopic study of intermediates produced by silver oxide oxidation (2) support the theory of quinone polymerisation for the autoxidation of catechin. Whereas quinone polymerisation of catechin and 5:7:3':4'-tetrahydroxyflavan involves the phloroglucinol residue, oxidative coupling of 5:7-di-0-methylcatechin and 3':4'-dihydroxyflavan resembles that of catechol. Further evidence for head-to-tail quinone polymerisation of catechin has been found in studies of the autoxidation of mixed phenolic substrates. Enzymic oxidation by mushroom, potato and tobacco polyphenoloxidases proceeds at a faster rate and lower temperature than the autoxidation of catechin, and gives a product precisely similar to the autoxidation polymer. The rate of oxygen uptake is proportional to the enzyme concentration The significance of the autoxidation and enzymic oxidation of catechin to the formation of phlobatannins is considered. Oxidation polymers of catechin are comparable with the tannins which have now been isolated in relatively large amounts from amongst tannin extracts of Acacia catechu and Uncaria gambir, plants valued for their phlobatannins (3). Special sections summarise the chemistry of catechin, the physical techniques on which much of this work depends, and the application of the theory of condensation polymerisation to the polymerisation of catechin. Three flavonols have been identified in extracts from Acacia catechu.

The Chemistry of Tanning Processes By K. H. Gustavson. Pp. ix + 403. (New York: Academic Press, Inc.; London: Academic Books, Ltd., 1956.) 9 dollars.