A comparative crystallographical study of the double selenates of the series R2M(SeO4)2,6H2O.—Salts in which M is Zinc

In two communications to the Chemical Society, the author presented the results of a detailed study of twenty-two salts of the series of monoclinic double sulphates R2M(SO4)2,6H2O, in which R was represented by potassium, rubidium, and cæsium, and M by magnesium, zinc, iron, manganese, nickel, cobalt, copper, and cadmium. The first of these memoirs dealt with the external morphology of the crystals, and the second with their internal physical properties. The present investigation refers to the less-known analogous double selenates, in which R is again represented by the alkali metals potassium(atomic weight 39), rubidium (atomic weight 85-2), and cæsium (atomic weight 132’7). The work on the group containing zinc has been completed, and the results are now communicated. Topsöe and Christiansen included in their well-known investigation the potassium salt of the group.