The u.v., visible, and i.r. spectra of several hydroxy-anthraquinones are discussed and the bands are assigned. These bands are compared with those of anthracene and anthraquinone. The band at 207 nm. is assigned to a n-6+ transition ; the bands at 252, 272, and 326 nm. are assigned by measuring spectra in solvents of various polarities. The stability constant for the 12-dihydroxyanthraquinone-ethanol complex is obtained.

The solution equilibria of di- and tetrapeptides containing tyrosine and glycine residues have been investigated in absence and presence of cobalt(II), nickel(II), and copper(II) ions. The equilibrium constants have been determined by pH titration at 30 °C and μ = 0.1 M(NaNO3) in 80% by weight DMSO – water mixed solvent. Protons are ionized from terminal (protonated amino and carboxyl) groups as well as from peptidic nitrogens. Complexes of 1:1 composition of metal ion – tetrapeptides were formed in quite a wide range of pH; also 1:1 complexes of the metal ions – dipeptides were formed in solution under the same conditions. Other higher complexes cannot be proved to form in the pH range studied. The complexes of these metal ions with glycine and O-Bzl-L-tyrosine were also studied under the same experimental conditions as control experiments and their equilibrium constants were calculated.

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