Extract
This substance is a combination of lime and sulphuric acid, in the proportion, according to Vauquelin, of 0,40 lime and 0,60 sulphuric acid. It has obtained various names: being called Chaux Sulfatée Anhydre by Haüy, Chaux Sulfatine by Brongniart, Anhydrite and Würfelpath by Werner, Muriacite by Poda and Klaproth, Pierre de Vulpino by Fleuriau de Bellevue, and Marmo bardiglio di Bergamo by the Italian statuaries. The name sulphate of lime has hitherto been applied to gypsum; but as it is now well known that the simple combination of lime and sulphuric acid produces bardiglione, while water is essential to the composition of the former, that expression is inapplicable, and might be supplied by that of Hydro-sulphate of lime.
Primitive Crystal A rectangular tetrahedral prism with square bases, which, from every indication, do not belong to the cube, but the height of which it has hitherto been impossible to determine, fig. 1.
Integrant Molecule The tetrahedral prism very distinctly exhibits natural joints’, parallel to the diagonals of its bases; the integrant molecule is therefore a right trihedral prism, having for its terminal face a right angled isosceles triangle, fig.2: the height of the integrant molecule as well as that of the primitive crystal, which is composed of four of these molecules, fig. 3,* is yet undetermined.
Fracture Even and shining in the direction of the cleavage; but having commonly more lustre, and often a pearly aspect, on those sides of the prism on which the Cleavage
- © The Geological Society 1811
XV. Memoir on Bardiglione or Sulphate of Lime, containing a Sketch of a Theory of the true Nature of Plaster, as well as of its Properties ; in order to determine the differences that exist between it and Bardiglione.
