Chemically, manganese is a dyad. It has the symbol Mn, and an atomic weight of 55 if 0=16, or 54.6 if H=1. It forms numerous oxides, the best known of which are (1) the monoxide, MnO, from which the manganous salts may be prepared, and which is itself ob tained by heating manganese carbonate out of contact with the air; (2) the sesquioxide, Mn,08, which exists in nature as the mineral braunite, and which is also formed when the monoxide is heated in air to a red heat; (3) the red or mangano-manganic oxide, Mn,O,, which corresponds to the magnetic oxide of iron, does not form salts, and exists in nature as the min eral hausmannite; (4) the black oxide, or di oxide, MnO,, which occurs in nature as pyro lusite and varvacite, and which is largely used in the arts in the preparation of oxygen and chlorine; (5) the trioxide, which is diffi cult of preparation and very unstable; and (6) the heptoxide, Mn,01, a heavy, dark green liquid, prepared by treating potassium permanganate with cold concentrated sulphuric acid. Several of these oxides also occur in a hydrated form, as minerals. Of the soluble manganous salts, the chief representatives are the sulphate and the chloride. Manganous sulphate, MnSO., is pre pared by treating the dioxide with sulphuric acid, oxygen being liberated at the same time in accordance with the equation MnOs+HsS0s= MnS0,-1-0-1-Hs0. It crystallizes with five molecules of water, as a pink-colored salt, and is used in dyeing and in medicine. The chloride, MnCls, crystallizes with four molecules of water, and is obtained as a by-product in the manu facture of chlorine by the action of hydrochloric acid upon manganese dioxide. It is used in cal ico printing. Of the insoluble manganese salts we may specially note the sulphide and the car bonate. The sulphide, MnS, is thrown down as a flesh-colored precipitate, when a soluble man gallons salt is precipitated by an alkaline sul phide. The carbonate, MnC0s, occurs native as the mineral rhodochrosite, and it may also be obtained as a white precipitate by adding an alkaline carbonate to a solution of manganeous sulphate or chloride.
Two other important classes of manganese compounds are known, in which the manganese does not act as a base, but as an acid-forming element. These are the manganates and per manganates, which may be regarded as the salts or acid," HsMnOs, and operman ganic HMnO., respectively. The potas sium salts of these acids are by far the most important ones. Potassium manganate, Kalin04, may be prepared by melting manga nese dioxide with caustic potash and a little po tassium chlorate, dissolving the bright" green mass so obtained in a •small quantity of water, and crystallizing by evaporation in a vacuum. Potassium manganate is used in laboratory operations, but it is very unstable, taking up oxygen with great readiness, and depositing hy drated dioxide of manganese. If the green solu tion containing potassium manganate be allowed to stand in the air, it absorbs oxygen, changes in color to a bright purple and deposits hy drated manganese dioxide. The purple color is due to the presence of potassium permanganate, KMn04, which may be obtained, by crystalliza ion, in the form of purple prismatic crystals. Potassium permanganate is a powerful oxidiz ing agent, and is extensively used in chemistry, in the arts and in medicine, on account of facility with which it parts with oxygen, espe cially in the presence of organic matter. It forms the basis of *Condy's fluid," which largely used as a disinfectant.
The chief ores of manganese are the black oxide pyrolusite (MnO,, 63.2 % Mn); psiknne lane (MnOs.1-120, 45-60 % Mn) ; braunite (3 MnSiO,, 69.7 % Mn) ; wad which is an earthy oxide (Mn 15-40 %) ; manganite (Mn,O,.H2O, 62.4 % Mn); rhodochrosite (MnC0s, 61.7 % MnO), and franklinite I(Fe3nMn)0(FeMn )2M. The ores are often associated with other metals, particularly with iron oxides, and with silver ores. Like residual
limonite (see IRON Oars) manganese ore is usu ally secondary, resulting from the removal of more soluble substances during the weathering of slightly manganiferous rocks. For many years prior to 1914 Russia was by far the great est producer of high grade manganese ores. Most of this output came from one locality near Chiatouri, south of the Caucasus Mountains. Some engineers have estimated the total re serves of high grade manganese ore in this one district to be upward of 100,000,000' tons, although this has been disputed. For some time before the war Russia's production averaged more than half a million tons yearly. Next in importance to Russia as sources of manganese are Brazil and India. In Brazil there has been a very rapid development of the industry and the production of manganese ore in 1917 is esti mated to have been about 500,000 tons. As the war has practically stopped the exportation of manganese from Russia and India, the de posits in Brazil have assumed very great importance. The United States has never been a large producer of manganese ore. A writer ia the Mineral Industry some years ago stated that the manganese output of the country was "insignificant because of the trifling character of the deposits.° In 1914 the total production in the United States of ore containing 40 per cent or more of manganese was only 2,635 long tons. In the production of ferromanganese and spiegeleisen and in the other arts using man ganese compounds it is desirable to have an ore containing at least 40 per cent of the metal. Before the late war it was almost impossible to find a steel maker willing to buy a lower grade. During the war some steel makers bought ore containing only 28 per cent man ganese and were glad to get it. Most of the manganese bearing ores mined in the United States are classified as manganiferous iron ores, which may or may not contain silver and lead. In these ores the manganese is mainly valuable as a flux in smelting operations, although it can sometimes be used for making spiegeleisen. The recent high prices have resulted in a ma terial increase in the domestic production of high grade ore and the output for 1917 is esti mated at about 120,000 tons. This amount is still much below the requirements. The United States Geological Survey has recognized the importance of the manganese situation and has recently issued a bulletin giving a list of all the shippers, prospective shippers and purchasers of manganese ores in the United States, com pleted up to 1 Oct. 1917. This list was re printed in the Engineering and Mining Journal for 26 Jan. 1918. It included the names of 171 individuals and companies producing or about to produce manganese ores, and 117 companies that are listed as purchasers. The shippers are located in 21 different States, of which the most important are Arizona, Arkansas, Cali fornia, Colorado, Georgia., I Minnesota Mon tana, Tennessee, Utah and Virginia. n 1910 the United States Geological Survey issued a very excellent monograph, Bulletin No. 427, entitled 'Manganese Deposits of the United States,' by Edmund Cecil Harden, giving very complete data in regard to ores, alloys, produc tion and uses. The same author contributed a paper entitled 'Manganese Ores of Russia, In dia, Brazil, and Chile,' to the 'Transactions of the American Institute of Mining Engineers' (Vol. LVI, p. 31). In the same volume there is an article by Joseph T. Singewald, Jr., and Benjamin Leroy Miller on 'The Manganese Ores of the Lafayette District, Minas Geraes, Brazil.' In the Engineering and Mining Journal (issue of 9 Feb. 1918) is a popular article by Henry V. Maxwell entitled 'Prospecting for Manganese.' See MINERAL PRODUCTION OF THE UNITED STATES.