Intelligence and Miscellajieoiis Articles. 3J3 



and quite different from the two preceding. The object was to 

 discover a substance which possesses, at a high temperature, the 

 property of water at common temperatures, or a little higher, with 

 respect to the substances which it holds in solution. It is well-known 

 that the evaporation of the water admits of the formation of many- 

 crystallized bodies. 



It is well-known that there are some substances which are volati- 

 lized at very high temperatures, and which are nevertheless powerful 

 solvents, when in fusion, of the greater number of metallic oxides ; 

 among these there may be cited boracic acid, borate of soda, phos- 

 phoric acid, and the alkaline phosphates. It seemed reasonable to 

 suppose that, by employing some one of these substances with cal- 

 culated proportions of certain oxides, and exposing the mixture to 

 a liigh temperature in open vessels, crystallized combinations might 

 be obtained by the evaporation of the solvent. Experiment perfectly 

 confirmed this conjecture. 



The author commences with the production of various minerals, 

 which may be considered as formed of a compound of one equivalent 

 of oxides constituted of two atoms of metal and three atoms of oxy- 

 gen, with one equivalent of an oxide constituted of one atom of 

 oxygen and one of metal. 



The greater number of these minerals are very hard, and belong 

 to the class of precious stones ; and they constitute a natural family, 

 comprehending a great number of species, as the spinelles, cymophane, 

 chromate of iron, oxidulated iron, &c. All these minerals, except 

 cymophane, are isomorphous, and generally crystallize in regular 

 octahedrons. The author attempted to produce some of these mi- 

 nerals by the method just described. 



Spine'lle. — This, as is well-known, is an aluminate of magnesia, 

 the formula of which is Al^ 0' MgO. Nature presents it to us pos- 

 sessing different colours. The red spinelle is that most valued by 

 lapidaries, and it owes its colour to about y^dth of oxide of chro- 

 mium. When the magnesia is partly replaced by protoxide of iron, 

 the varieties are more or less coloured and opake ; all crystallize in 

 regular octahedrons, slightly or not at all modified, with the exception 

 of the variety known by the name of pleonaste, which crystallizes in 

 rhombic dodecahedrons. 



The hardness of the natural spinelle is 8 ; it scratches quartz readily ; 

 its density varies from 3-523 to 3-585. 



All varieties are infusible by the blowpipe. The red varieties 

 become black and opake ; on cooling they assume, by transmitted 

 light, a greenish tint, and then their original colour is restored. 



M. Ebelmen then proceeds to state, that having weighed eacli of 

 the fixed matters separately which were to enter into the compound, 

 and tlie fused boracic acid reduced to powder, the whole was heated 

 on a sheet of platina in the mode which the author details. Various 

 l)rccious stones were formed, as siiinelle of various colours and co- 

 lourless, and cymoi)hane, and several otiicr crystalline compounds. 

 To give an example cf the method adopted, and the success attend- 

 ing it, wc will (juotc the formation of llic rose-coloured spinelle. 



