Manganese

(măng-gah-neez'.) (Chem.) A metallic element, compounds of which have been known from very early times, although it was not until 1774 that the metal was isolated by Gahn. At. weight 55, symbol Mn, sp. gr. 8.013. In the pure state, M. is a white brittle metal, which melts only at the highest heat ofa blast furnace. It oxidizes both in air and water, and di olves easily in dilute mineral acids. It is slightly magnetic. M. forms several oxides, the most important of which are the following: - The prot oxide (MnO). This is obtained hydrated as a white precipitate on adding an alkali to a proto salt of M.; it oxidizes very readily. It unites with acids to form a well-defined series of salts. -The Peroxide or Dioxide (MnO2), which is met with native as pyrolusite. It forms bluish-black, metallic looking crystals of sp. gr. 4-9, opaque and infusible before the blowpipe. Its great use in manuf. is as an oxidizing agent, as it parts with some of its oxygen, and is reduced to the red oxide when exposed to heat. It is largely used in the preparation of oxygen, in the manuf. of chlorine, and for decolorizing gla .- Under the names of psilomelane, varve site, wad, ., occur native oxides of M. of no very definite constitution, but which appear to be mixtures of oxides previously described. -Permanganic Acid (HMnO4). This is the highest state of oxidation of the metal. In the pure state it is a thick syrupy liquid of a greenish metallic lustre. When gently heated it volatilizes, forming violet vapors which condense without decomposition. If the heat is not applied cautiously, it decomposes with explosion. P. A. is one of the most powerful oxidizing agents known, instantly igniting some combustible bodies when added to them, and exploding with others. It forms well-defined salts with bases, of which, however, we need only mention the following:-Permanganate of Pota ium (KMnO4), crystallizes in long deep red needles, which are permanent in the air and di olve in about sixteen parts of cold water. A solution of P. of P. is of great use both in the laboratory, as a convenient oxidizing agent and standard test liquid, and also as a harmle and powerful deodorizing agent for household purposes. [s. 574]