A dictionary of chemistry, on the basis of Mr. Nicholson's: in which the principles of the science are investigated anew, and its applications to the phenomena of nature, medicine, mineralogy, agriculture, and manufactures, detailed (Volume 2).

  • Ure, Andrew, 1778-1857.
Date:
1821
Catalogue details

Licence: Public Domain Mark

Credit: A dictionary of chemistry, on the basis of Mr. Nicholson's: in which the principles of the science are investigated anew, and its applications to the phenomena of nature, medicine, mineralogy, agriculture, and manufactures, detailed (Volume 2). Source: Wellcome Collection.

Provider: This material has been provided by the National Library of Medicine (U.S.), through the Medical Heritage Library. The original may be consulted at the National Library of Medicine (U.S.)

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    CHEMISTRY. EAR EAGLE-STONE. A clay ironstoTie. * EARTHS. Fifteen years ago, few ■substances seemed more likely to retain a permanent place in chemical arrange- ments, than the solid and refractory earths, which compose the crust of the globe. Analysis had shown, that the various stony or pulverulent masses, which form our mountains, valleys, and plains, might be considered as resulting from the combina- tion or intermixture, in various numbers and proportions, of nine primitive earths, to which the following names were given: 1. Barytes. 2. Strontites. 3. Lime. 4. Magnesia. 5. Alumina, or clay. 6. Silica. 7. Glucina. 8. Zirconia. 9. Yttria. Alkalis, acids, metallic ores, and native metals, were supposed to be of an entirely dissimilar constitution. The brilliant discovery by Sir H. Davy in 1808, of the metallic bases of potash, soda, barytes, strontites, and lime, subvert- ed the ancient ideas regarding the earths, and taught us to regard them as all belong- ing, by most probable analogies, to the me- tallic class. According to an ingenious suggestion of Mr. Smithson, silica, howev- er, ought to be ranked with acids, since it has the power in native mineral compounds of neutralizing the alkaline earths, as well as the common metallic oxides. But as this property is also possessed by many metallic oxides, it can afford no evidence against the metallic nature of the siliceous basis. Alumina, by the experiments of Ehrman, may be made to saturate lime, producing a glass; and the triple com- pounds of magnesia, alumina, and lime, are perfectly neutral, in porcelain. We might therefore refer alumina as well as silica, to the same class with the oxides of antimony, arsenic, chromium, columbium, molybde- num, titanium, and tungsten. Alumina, however, bears to silica, the same relation that oxide of antimony does to that of arse- EGE nic; the antecedent pair acting the part of bases, while the consequent pair act only as acids. The compound of the fluoric principle with silica is of too mysterious a nature to be employed in this discussion. The almost universal function which silica enjoys of saturating the alkaline oxides in the native earthy minerals, is exhibited, in a very striking manner, in Mr. Allan's val- uable Synoptic Tables. From his fifth to his fifteenth table of analyses, the column of silica is always complete, whatever de- ficiency or variation may occur in the co- lumns of the earthy bases. At leasi, only a very few exceptions need be made for the oriental gems, which consist of strongly ag- gregated alumina. To the above nine earthy substances', Berzelius has lately added a tenth which he calls thorina* j See soil and analysis of soils, f Earthenware. See Pottery. Eao db Luce, consists chiefly of the es- sential oil of amber and the volatile alkali. Echini. Calcareous petrifactions of the echinus, or sea hedgehog. Effervescence is the commotion pro- duced in fluids by some part of the mass suddenly taking the elastic form, and es- caping in numerous bubbles. Efflorescence is the effect which takes place when bodies spontaneously become converted into a dry powder. It is almost always occasioned by the loss of the water of crystallization in saline bodies. * Egeran. A sub-species of pyramidal garnet. Colour reddish-brown. Massive, sometimes crystallized in rectangular four- sided prisms, with cylindrical convex late- ral planes. The prisms are long, and deep- ly longitudinally streaked. Shining, vitre- ous. Cleavage, twofold. Fracture, uneven. Feebly translucent on the edges. Scratch- es feldspar. Brittle. Sp.gr. 3.294. It melts into a black scoria. It occurs in a bed of