Reduction of metal calces

The particular field of chemical theory and practice to which their selection of substances pertained is plainly indicated by the chemical operations connecting the substances of the table s classes. Focusing on the classes that were well-established before the Methode—Xht classes of the traditional salifiable bases (I/c-e), the acids (Ill/b), the metal oxides or metal calces (in/c), the salts (V/b-c), and the alloys (VI/c)—we find three basic types of chemical processes involved first, those in acid solutions, mainly in connection with the production or decomposition of salts second, calcination of metals and reduction of metal calces and third, the combination of metals into alloys. 

Higgins s Comparative View is mostly concerned with a clever refutation of Kirwan s Essay on Phlogiston (1787), the French edition (see p. 662) being also mentioned as seen first after the section on the marine acid was completed. The sections deal with the composition and decomposition of water (p. i), the composition of acids (p. 8), vitriolic acid (p. 18), nitrous acid (p. 82), marine acid (p. 179), the calcination of metals via sicca (p. 219), the calcination of metals by steam and the decomposition of water (p. 240), the reduction of metallic calces by charcoal and the formation of fixed air (p. 249), the solubility of metals (p. 254)> the precipitation of metals by each other (p. 259), and (as an appendix) an analysis of the human calculus with observations on its origin (p. 283), which the preface (p. xiii) says was sent to the Royal Society in 1787 and read in Spring 1788 (it was not published and is in the archives of the Royal Society). 

Martinus Van Marum examined the revivification of metallic calces and the calcination of metal wires by electric sparks from a powerful machine. He confirmed the reduction of calces, reported by de Milly but denied by Brisson and Cadet, with red lead, white lead, and oxides of zinc, antimony,... 

Thiogiston is not attracted towards the centre of the earth, but tends to rise thence comes the increase of weight in the formation of metallic calces and the diminution in weight in their reduction... 

Chemical analyses of the oxygen content of these crystals, carried out by (1) careful oxidation to molybdenum(VI) oxide in a stream of oxygen and (2) carbon reduction of the metal, yielded the following data. Anal. Calcd. for Mo02 O, 25.01. Found, 25.1. Mo 0 ratio, 1 2.01. Calc, for W02 O, 14.83. Found, 14.9. W 0 ratio, 1 2.01. 

Actinium — (Gr. aktis, aktinos, beam or ray), Ac at. wt. (227) at. no. 89 m.p. 1050°C, b.p. 3198°C sp. gr. 10.07 (calc.). Discovered by Andre Debierne in 1899 and independently by F. Giesel in 1902. Occurs naturally in association with uranium minerals. Thirty-four isotopes and isomers are now recognized. All are radioactive. Actinium-227, a decay product of uranium-235, is an alpha and beta emitter with a 21.77-year half-life. Its principal decay products are thorium-227 (18.72-day half-life), radium-223 (11.4-day half-life), and a number of short-lived products including radon, bismuth, polonium, and lead isotopes. In equilibrium with its decay products, it is a powerful source of alpha rays. Actinium metal has been prepared by the reduction of actinium fluoride with lithium vapor at about 1100 to 1300°C. The chemical behavior of actinium is similar to that of the rare earths, particularly lanthanum. Purified actinium comes into equilibrium with its decay products at the end of 185 days, and then decays according to its 21.77-year half-life. It is about 150 times as active as radium, making it of value in the production of neutrons. Actinium-225, with a purity of 99%, is available from the Oak Ridge National... 

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