Change in some properties of phenolphthalein and thymolphthalein as a result of plastic deformation under high pressure

Conclusions

• 1. A study of the dependence of the shear on the pressure for solid phenolphthalein and solid thymolphthalein has permitted the observation of the presence of jump-like irreversible changes at pressure of 12–15 and 14–16 kbar, respectively; an X-ray investigation has shown these changes correspond to a disordering of the crystal lattice of the indicators mentioned.

• 2. The plastic deformation of phenolphthalein and thymolphthalein under a high pressure leads to the appearance of unpaired electrons; for phenolphthalein their concentration rises from 10¹⁴-10¹⁵ g⁻¹ at ∼ 23 kbar to ∼10¹⁷ g⁻¹ at 50 kbar, and for thymolphthalein from 10¹⁴-10¹⁵ g⁻¹ at ∼17 kbar to ∼10¹⁷ g⁻¹ at 50 kbar.