AbstractStability constants of titanium (IV), zirconium and thorium‐hinokitiolate chelates have been calculated from spectrophotometric data in 50% ethanol‐water solution at 25°. It has been found that the stability constant and the optimumpH of the various metal chelates increase with the increase in the atomic number of metals. The order of stability for the metals is the same as that found for other types of coordinating agents. Zirconium and thorium combine with four hinokitiolate ions, while titanium (IV) combines with only two hinokitiolate ions to form a chelate compound. A list of molar absorption coefficients is given and the photometric sensitivities of these metals with hinokitiol were determ