A new technique is described by which pressures of 50,000 kg/${\mathrm{cm}}^2$ and more may be applied to solids, and the parameters of any transitions measured. A systematic examination has been made for polymorphism of many of the elements in the new pressure range. New modifications are found for Bi, Hg, Tl, Te, Ga, and ${\mathrm{I}}_2$, and the transition parameters measured. A beginning has been made of a systematic study of polymorphism of compounds, and results obtained for KCl, KBr, and KI, which assume at about 20,000 kg/${\mathrm{cm}}^2$ presumably the CsCl type of structure.

• Received 26 September 1935

DOI:https://doi.org/10.1103/PhysRev.48.893