Manganese, a metal having the symbol Mn and the combining weight 55, long known in the mineral pyrolusite, used to neutralize the green color of glass. The ores containing it were variously styled female magnets, magnesia nigra in contradistinction to magnesia alba, alabandine from the city of Alabanda, manga-v desum by the glass makers, and subsequently by different chemists manganesium, mangani-um, and finally manganese. In 1774 Scheele and Bergman described the black oxide as a peculiar earth, and Gahn afterward succeeded in isolating the metal from it by mixing the pulverized mineral with charcoal and oil, forming the mass into pellets, which were introduced into a brasqued crucible and exposed for an hour to the highest heat of a forge. The metal obtained in this way is very brittle, and, like cast iron, contains silicon and carbon, and has a variable specific gravity. Brunner adopted a method analogous to the one employed in the preparation of aluminum; the chloride of manganese was fused with an equal weight of fluor spar and'one fifth its weight of metallic sodium.
The metal thus prepared is very hard and brittle, will take a tine polish, cannot be scratched by a file, cuts glass easily, does not change in moist air, is not attracted by a magnet and is not itself magnetic, and has the specific gravity of 7.16. Deville reduced manganese oxide by mixing it with one tenth its weight of sugar charcoal and exposing it for three hours to a white heat in a lime crucible enclosed in a brasqued crucible. The product was a crystalline mass, the powder of which decomposed water rapidly; color like bismuth; specific gravity 8.015. Loughlin has subjected the above methods and numerous others to a careful repetition in his laboratory, and comes to the conclusion that the task of producing perfectly pure manganese is one of great difficulty. The discrepancy between the specific gravities, ranging from 6.85 to 8.015 as given by different experimenters, leads to the conclusion either that manganese has several allotropic modifications, or that the pure metal has not yet been made. - Some of the alloys of manganese are of great value. "With copper it yields a product which possesses the color and properties of German silver, while costing much less.
Elliot Savage of West Meriden, Conn., has invented a process for preparing this alloy by reducing pyrolusite and copper ore directly in a gas furnace. Dr. Prieger of Bonn and Valenciennes of Paris have prepared several alloys of manganese and iron and manganese and copper. An intimate mixture of black oxide of manganese, powdered charcoal, and iron filings or turnings is made in a black-lead crucible holding 30 to 50 lbs. A covering is made of charcoal, fluor spar, and common salt, and the contents of the crucible are exposed for several hours to a white heat. The alloy of manganese and copper is prepared in a similar way, and both are very hard and capable of a high polish. In England there are 36 patents involving the use of manganese in iron and steel, the earliest of which was taken out in 1799. Berthier made a large number of alloys of manganese, and described their properties. Much use is now made of manganese in the metallurgy of iron and steel, and the frank-linite ore of 'New Jersey is largely employed in the United States in the manufacture of crystalline burglar-proof iron and spiegel iron - Manganese does not occur native, but is found widely diffused in association with other elements.
The following are the principal manganese minerals, the first being the chief ore of commerce: pyrolusite, braunite, manganite, rhodonite, hausmannite, alabandine, diallagite, wad, psilomelane, franklinite, credneritc, col-umbite, wolfram, triphiline, and manganese alum. Mines of manganese have been worked at Bennington, Vt., West Stockbridge and Sheffield, Mass., and later in North Carolina and Virginia. In 1871 $20 a ton was paid in -New York for 70 per cent. Virginia ore. The annual production of manganese ore in Europe may be approximately stated as follows:
Huelva, Spain. 1,000.000 cwts.
Prussia....... 531.422 "
Thuringia..... 32,103 "
Saxony......... 1 8,579 cwts.
Sweden........ 2,400 "
Nearly nine tenths of the manganese of commerce is consumed in the manufacture of chlorine and bleaching powders; the other tenth is employed in the following industries: to color and decolorize glass; in the manufature of iron and steel; in the painting and glazing of porcelain and pottery; in the production of oxygen; and in the preparation of the various Baits required in medicine and the arts. - -Manganese enters as a base into two classes of compounds, the manganous and manganic; and also as an acid into two classes of salts, the manganates and permanganates. There arc five well characterized oxides. 1. Manganous oxide, or manganese monoxide, MnO, is a basic body furnishing a series of manganous salts, pink-colored, which rapidly absorb oxygen, and pass into a higher state of oxidation. The pure oxide is a greenish powder obtained by heating the carbonate in absence of air; the hydrate is precipitated as a white gelatinous mass, when an alkali is added to a solution of a manganous salt.
Of the manganous salts the chief soluble ones are the sulphate, MnS04 +5H20, and the chloride, MnCl2+4H2O. The sulphide, MnS, and the carbonate, MnC03, are insoluble. 2. Manganic oxide, or manganese sesquioxide, Mn2O3, exists in nature as braunite, and may be prepared artificially by exposing manganous oxide to a red heat. It forms a series of insoluble salts, of which manganese alum is one of the most interesting. 3. Red or mangano-nianganic oxide, Mn304, is a neutral body, corresponding to the magnetic oxide of iron, and occurring in nature as hausmannite. 4. Black oxide or manganese dioxide, MnO2, is the chief ore of commerce, the magnesia nigra of the ancients, and termed pyrolusite by modern mineralogists. It can be artificially formed by adding a solution of bleaching powder to a manganous salt. This compound yields one third of it-oxygen when heated to redness, and one half its oxygen when heated with sulphuric acid. According to Gorgeu, MnO2 is capable of forming manganite salts with alkaline bases. 6. Permanganic acid, H2Mn208, is a dark green heavy liquid, obtained by the action of strong cold sulphuric acid upon potassium permanganate. Manganic trioxide, its corresponding hydrate, manganic acid, and the anhydride of permanganic acid, are not known in a free state.
The salts of the permanganates, notably the potassium permanganate, are now largely employed as disinfectants, for bleaching, and in the laboratory for the purpose of volumetric analysis. Among numerous methods for the preparation of potassium permanganates, the following may be recommended: 500 lbs. of freshly prepared potash lye of 46° B. are mu with 105 lbs of pure potassium chlorate, and concentrated by evaporation in an iron kettle; and then, under constant stirring. 182 lbs. of finely pulverized black oxide of manganese are added, and the heat continued until the whole is fluid; it is then stirred until cold; the granular mass is again heated to redness in small iron kettles until it is wholly fused, and is then, after cooling, broken up, boiled with water in a large pot, and allowed to settle; the clear liquor is decanted and evaporated to crystallization. In this way. from 180 lbs. of oxide of manganese, 98 to 100 lbs. of potassium permanganate, in beautiful long needles, can be obtained.
For the bleaching of en-gravings and paper stock, for the purification of drinking water, as a disinfectant in hospitals, as a deodorizer of tainted meat in culinary operations, as a tooth wash under the name of Condy's liquid, for the evolution of ozone oxygen, and for chemical analysis, there are few agents more valuable than potassium permanganates. - Various colors or dyes are prepared from salts of manganese. Nuremberg violet is made by fusing finely pulverized pyrolusite and phosphoric acid in proper proportions, di-ing in ammonia, filtering, evaporating to dryness, and treating with water, when a violet powder remains. Barium manganate affords a tine green pigment, much safer than arsenic colore Potassium permanganate dyes wood in imitation of mahogany and nut wood. The employment of manganese in glass manufacture was one of the earliest uses of this element. The oxide of manganese is put into the glass mixture to counteract the effect of oxides of iron; but in course of time it is itself oxidized by the light and air, and colors the glass red. As red glass intercepts the chemical rays of light, the skylights of photographers and the sashes of greenhouses have to be provided with glass to which no manganese has been added.
The manufacture of oxygen on a commercial scale, according to the process of Tessie du Motay, is founded upon the property of the black oxide of manganese, when fused with caustic soda, to take up oxygen from a current of hot air, which it yields up again to superheated steam, thus offering a cheap and continuous process. - As the principal application of the oxides of manganese is in the manufacture of bleaching powders, their commercial value depends upon the amount of oxygen they can furnish, or, which comes to the same thing, the quantity of chlorine which they are capable of eliminating when treated with hydrochloric acid. The methods of assaying the oxides of manganese maybe classed under four heads: 1. The determination of the amount of oxygen disengaged by sulphuric acid; 2, the oxidation of oxalic acid; .3. the evolution of chlorine rrom hydrochloric acid; 4, volumetric estimation lor the details of these methods the reader is referred to Fresenius's "Chemical Analysis. the chloride of manganese, obtained by crystallization from the residues in the manufacture of chlorine from the dioxide and hydrochloric arid, is regenerated so as to recover the dioxide to be employed again by neutrahzing its solution with excess of manga-nese and treating with hypochlorite of lime; by slightly derating the temperature chlorine is disengaged, and the hydrate of the dioxide is precipitated in great purity, thus accomplishing a great saving in the quantity of hydrochloric acid and manganese required in this important industry. - Several salts of manganese have been used in medicine, the most important of which are the dioxide, iodide, sulphate, and phosphate, and permanganate of potassium.
The first of these is said, when slowly introduced into the system, as happens to those engaged in grinding the mineral, to act as a poison, finally inducing paraplegia; but this is by no means a common occurrence. It has been used as a tonic, and also as a local remedy in dyspepsia. The iodide, sulphate, and phosphate are used together with or instead of the corresponding salts of iron, and are supposed to have a similar action. Minute quantities of manganese have been found in the body, but it is extremely doubtful whether its presence is of physiological importance, or is in fact anything more than an accident. Although the therapeutic value of these compounds may be cloubted on theoretical grounds, yet practically they have been occasionally found of service. Cases of anaemia that have proved rebellious to chalybeates will sometimes yield to the salts of manganese. In chronic nervous debility also these salts sometimes act favorably as a tonic to the nervous system in some unexplained way. The dose of the sulphate of manganese is from 5 to 10 grains.
The sirup of the iodide is one of the best preparations of manganese for medicinal use; its dose is from 10 to 20 drops three times a day, and should be given in water soon after eating.