The dissociation constants of organic peracids have been determined by potentiometric titrations ; they lie in the range of pK 7-8. U.-v. absorption spectra of hydroperoxides were used to assess their (classical) dissociation constants, the logarithms of which lie between 11-5 and 12.8. These data agree with the structure generally ascribed to the peracids. In the peroxide series, however, methyl substitution has less effect than usual : the reasons for this are discussed in terms of Walsh's theory of the peroxide bond.

The hitherto accepted structures for ( + )-tubocurarine chloride and (+ )-chondrocurine have been found to be incorrect; the former is a mono-not a diquaternary salt, the latter being the related tertiary base.

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Aspidospermine methiodide and deacetyl-N-methylaspidospermine dimethiodide have been prepared, and the nature of deacetyl-N-methylaspidospermine monomethiodide has been established. Thermodynamic dissociation constants of aspidospermine and several derivatives are recorded. A tentative structure for aspidospermine is discussed from the biogenetic aspect. ASPIDOSPERMINE (Ia) does not react with methyl iodide at room temperature,l and previous attempts to prepare a methiodide at elevated temperature have resulted only in ill-defined, amorphous products. However, a crystalline methiodide (IIa) has now been obtained by prolonged interaction of the components at 56". The rather sluggish reactivity of the basic nitrogen atom, N(b), is most probably due to steric hindrance, since its basic strength (see Table ) is comparable with that of strychnine, for example, which reacts readily with methyl iodide.

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