Memoirs of the National Academy of Sciences Volume 13 (Paperback)

This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1915 Excerpt: ...which are generally pretty uniformly distributed, though at times aggregated to cause cloudiness. As a rule only the cube is present, but occasionally the octahedron appears in part subordinate, in part equal with the cube. Most of the crystals are ideally formed, but occasionally prismatic through a stronger development of four faces of the cube in one zone. Somewhat more common, but still rare, are cube faces indented by growth along the edges. Most of the crystals are 0.03 to 0.04 mm. in size, but the dimensions rise to 0.09 and sink to 0.01 mm. The following properties were verified: Completely isotropic; index of refraction between 1.48 and 1.52; specific gravity, 2.3; no cleavage; not attacked by concentrated HC1 or aqua regia; soluble in cold hydrofluoric acid; unchanged B. B. A few opaque grains (apparently chromite), as well as cloudy, apparently very much disintegrated silicate grains, accompany the cristobalitelike silica. Although the number of the cristobalitelike crystals was very considerable, it was not possible, on account of their small dimensions, to obtain enough material for an analysis. The amorphous carbon behaves, under treatment with potassium chlorate and nitric acid, exactly as Moissan describes. The oxidation proceeds with extreme slowness, but it develops no trace of carbonic acid. Without closer investigation the carbon would be taken from its appearance for graphite, and this graphitic character may account for the resistance to strong oxidizing agents. The dark fragments remaining after treatment of the insoluble residue with copper ammonium chloride, and which--disregarding the schreibersite inclusions--have the appearance of a homogeneous substance, were analyzed in the supposition that they were particles of eisenglas. The...