Lattice constants of synthetic chalcanthite by the x-ray precession technique using a single mounting of the crystal

Chalcantbite is herewith returned to its pre-Barker setting with α and β obtuse, γ acute (rather than β and γ obtuse, α acute), but otherwise no change except for refinements m detail. The x-ray precession technique as applied to a triclinic crystal with but a single mounting is described for (1) precession along two axes, and (2) precession along but a single axis. A new angle table has been prepared.