312 Intelligence and Miscellaneous Articles. 



sesses of dissolving metallic oxides in the dry way, and the volati- 

 lity of this acid at a high temperature. It occurred to him that by 

 dissolving alumina and magnesia, mixed in the proportions which 

 constitute spinelle, in fused boracic acid, and exposing the mixture 

 in open vessels to the high temperature of a porcelain furnace, that 

 the affinity of the alumina for the magnesia might cause the separa- 

 tion of a crystallized aluminate and the expulsion of the boracic acid. 

 The proportions employed were about one part of fused boracic 

 acid, and two parts of a mixture of alumina and magnesia, composed 

 so as to constitute the compound Al'-^ O^ MgO ; and from ^^ to 

 2-g-o of bichromate of potash were added to it. The ingredients, 

 well-mixed, were placed on platina foil, in a cup of porcelain, and 

 exposed to the highest temperature of the porcelain furnace of Sevres. 

 A product was obtained the surface of which was covered with cry- 

 stalline facets, and the interior contained cavities sprinkled with 

 crystals, the form of which was readily distinguishable with a glass. 

 These crystals were rose-red, transparent, scratched quartz readily, 

 and had the form of the regular octohedron without any modifica- 

 tion. They were completely infusible by the blowpipe. These 

 characters, combined with the composition of the crystals as deduced 

 from synthesis, appear to M. Ebelmen sufficiently conclusive as to 

 their identity with spinelle. 



By substituting the equivalent of protoxide of manganese for 

 magnesia, a crystalline product was obtained in large laminae, ex- 

 hibiting the form of equilateral triangles or regular hexagons. The 

 author considers these as constituting the manganesian spinelle Al^O' 

 MnO, which has not hitherto been met with in the mineral kingdom. 



Oxide of cobalt substituted for magnesia, equivalent for equiva- 

 lent, yielded crystals of a black-blue colour, in regular octohedrons. 

 They also scratched quartz, but not so readily as the two preceding. 



In employing alumina and glucina in the proportions which con- 

 stitute cymophane AP O^ GIO, a mass covered with crystalline 

 asperities of great splendour was obtained. This product scratched 

 quartz and even topaz distinctly ; it therefore possessed hardness 

 comparable to that of natural crystallized cymophane. 



Certain silicates, which are infusible by the heat of our furnaces, 

 appear also to be produced by the same process. Thus, on fusing 

 the elements of emerald with half their weight of boracic acid at the 

 same temperature as in the preceding experiments, a substance is 

 obtained which easily scratches quartz, and its surface presents a 

 great number of facets, the form of which is the regular liexagon. 



The author proposes to continue these experiments, but at pre- 

 sent only states in addition, that it is possible to produce at tempe- 

 ratures lower than those obtainable in our furnaces, diaphanous 

 crystals, the hardness and external characters of which are analogous 

 to those of precious stones ; and he also concludes that many mi- 

 neral species may be formed at a lower temperature than that re- 

 quired for their fusion. — Comptes Rendus, August 16, 1847. 



