MAN'GANESE (symb. Mn, equiv. 27.6; new system, 55—spec. gray. 8) is one of the heavy metals of which iron may be taken as the representative. It is of a grayish white color, presents a metallic brilliancy, is capable of a high degree of polish, is so hard as to scratch Vass and steel, is non-magnetic, and is only fused at a white heat. As it oxidizes rapidly on exposure to the atmosphere, it should be preserved under naphtha.
It occurs in small quantity, in association with iron, in meteoric stones; with this exception it is not found native. The metal may be obtained by the reduction of its sesquioxide by carbon at an extreme heat.
31anganese forms no less than six different oxides—viz., protoxide (Mn0), sesqui oxide (31n203), the red oxide (Mn30.), the binoxide or peroxide (Mn02), manganic acid (Mn03), and permanganic acid (Mn,07). The protoxide occurs as an olive-green powder, and is obtained by igniting carbonate of manganese in a current of hydrogen. Its salts are colorless, or of a pale rose color, and have a strong tendency to form double salts with the salts of tun monia. The carbonate forms the mineral known as manganese spar. The sulphate is obtained by heating the peroxide with sulphuric acid till there Is faint ignition, dissolving the residue in water, and custallizing. It is employed largely in calico-printing. The silicate occurs in various minerals.
The sesguioxide is found crystallized in an anhydrous form in braunite, and hydrated in manganite. It is obtained artificially as a black powder by exposing the peroxide to a prolonged heat. When ignited it loses oxygen, and is converted into red oxide. Its. salts are isomorphous with those of alumina and sesquioxide of iron. See ISOMORPMS3L It imparts a violet color to glass, and gives the amethyst its characteristic tint. Its sulphate is a powerful oxidizing agent.
The red oxide corresponds to the black oxide of iron. It occurs native in kausrnann ite, and mv be obtained artificially by igniting the sesquioxide or peroxide in the °pert air. It is a compound of the two preceding oxides.
The binoxide, or peroxide, is the black manganese of commerce and the pyrolusite of' mineralogists, and is by far the most abundant of the manganese ores. It occurs in a hydrated form in varmcite and wad. Its commercial value depends upon the propor tion of chlorine which a given weight of it will liberate when it is heated with hydro chloric acid, the quantity of chlorine being proportional to the excess of oxygen which. this oxide contains over that contained in the same weight of protoxide. The reaction: is explained by the equation— Binex. Mang. Hyd. Acid. Chlor. of Mang. 'Water. Chlorine.
Mg°, 2HCI = MgC1 2H0 ± CI When mixed with chloride of so.dium and sulphuric acid it causes an evolution of"
chlorine, the other resulting products being sulphate of soda and sulphate of protoxide-. of manganese, as shown in the equation— NaCI-FMn0,-F2S0.=Na0, SO .-1-3InO, SO,+Cl.
When mixed with acids it is a valuable oxidizing agent. It is much used for the preps.. ration of oxygen (q.v.), either by simply heating it, when it yields 12 per cent of gas, or by heating it with sulphuric acid, when it yields 18 per cent. Besides its many uses. in the laboratory, it is employed in the manufacturing of glass, porcelain, etc.
Nanganic acid is not known in a free state. Manganate of potash is formed by fusing together hydrated potash and binoxide of manganese. The black rnass which. results from this operation is soluble in water, to which it communicates a green color, due to the presence of the manganate. From this water the salt is obtained in vacuo in. beautiful green crystals. On allowing the solution to stand exposed to the air it rapidly becomes blue, violet, purple, and finally red, by the gradual conversion of the manganate into the permanganate of potash; and on account of these changes of color the black mass. has received the name of mineral chameleon..
Permanganic acid is only known in solution or in a state of combination. Its solution, is of a splendid red color, but appears of a dark violet tint when seen by transmitted, light. It is obtained by treating a solution of permanganate of baryta witlfsulphuric acid„ when sulphate of baryta falls and the permanganic acid remains dissolved in the water. Permanganate of potash, which crystallizes in reddish purple prisms, is the most impor tant of its salts. It is largely employed in analytical chemistry, and is the basis of. Condy's disinfectant fluid.
Manganese is a constituent of many mineral waters, and is found in small quantity in the ash of most vegetable and animal substances. It is almost always associated with iron.
Various preparations of rnanganese have been employed in medicine. The sulphate of the protoxide, in doses of one or two drams, produces purgative effects, and is sup posed to increase the excretion of bile; and, in small doses, both this salt and the car bonate have been given with the intention of improving the condition of the blood in cases of anmmia. Manganic acid and permanounate of potash are of great use when applied in lotions (as in Condy's fluid diluted) to:ifoul and fetid ulcers. In connection with the medicinal applications of manganese, it may be mentioned that manganic acid. is the agent employed in Dr. Angus Smith's celebrated test for the impurity of the air.