BINOXIDE OF MANGANESE.
71;
Order XXVIII.— BINOXIDE OF MANGANESE.
MANGANE'SII BINOX'YDUM.—BINOXIDE OF MANGANESE.(Manganesii Oxidum, E.)
History. —Native binoxide of manganese has been long known and used inthe manufacture of glass (Magnesia Vitriariorum;) biit until Kaim, in 1770,succeeded in extracting a peculiar metal from it, it was usually regarded as anore of iron. It is commonly termed Native Black or Peroxide of Manganese, orfor brevity Manganese.
Natural History. —The oxide of manganese used in chemistry and pharmaeyis the native anhydrous binoxide, called by mineralogists Pyrolusite. It is foundin great abundance in Cornwall, Devonshire, Somersetshire, and Aberdeenshire,from whence most of what is met with in commerce in this country is obtained.The prineipal mines of it are in the neighbourhood of Launceston, Lifton, andExeter. The Upton Pyne mine, once celebrated for its oxide of manganese, hasyielded scarcely any for several j'ears past, if, indeed, it be not completely workedout. Pyrolusite is also found in Saxony, Hungary, France, and other countriesof Europe.
Preparation. —Native 1 binoxide of manganese after besing raised from the mineis broken into small pieces, about the size of peas, and theri washed to separatethe earthy impurities. It is afterwards ground in mills to an impalpable powder.
Properties. —This mineral oecurs massive, columnar, crystallized, and pulve-rulent: the form of the crystals is the right rhombic prism. The massive varietyhas sometimes a metallic lustre, bnt is generally dull and earthy: its colour is ironblack or brownish: it soils the fingers in handling it: its sp. gr. varies from 4-6to 4/9: itis tasteless, odourless, and insoluble in water: it yields a black powder.
Characteristics. —When heated it yields oxygen gas. Mixed with commonsalt and sulphuric aeid it gives out chlorine. Heated with sulphuric aeid itevolves oxygen, and forms a sulphate of the protoxide of manganese. It is inlu-sible before the blow-pipe; dissolves infused borax with effervescence, and coloursthe globule of an amethystine colour. If it be digested in hydrochloric aeid untilchlorine eease to be evolved, and the Solution be slighlly supersaturated with am-monia, we get rid of the sesquioxide of iron: the filtered liquid throws down awhite preeipitate with ferroeyanide of potassium.
Composition. —Pure binoxide of manganese has the foilowing composition:—
Jiioms. Eq. Wt.
Manganese............ 1 ........ 28 .
Oxygen................ 2 ........ 16 .
BerzcliusandForchammer. Jlrfvcdaoa.
(53-5 ........ <>375 ........ 64 02
30-5 ........ 302.5 ........ 3508
Per Cent.
Binoxide of Manganese. I
1Ü00 ........ 100-00
10000
Purity. —The native binoxide is, however, never pure: it usually contains oxideof iron, carbonate of lime, sulphate of baryta, and argillaceous matter. Its purityis judged of by the quantity of oxygen which it is capable of yielding; or of thequantity of chlorine set free when this oxide and hydrochloric aeid are allowed toact on each other. The quantity of chlprine set free can be estimated by thequantity of protosulphate of iron which it peroxidizes. (Graham, Elements ofChemistry, p. 536.) The brown varieties are inferior to the black ones.
Muriaüc aeid aided liy lieat dissolves it almost entirely, disengaging ehlorine: heat disen-gages oxygen. Ph. Ed.
Physiological Effects. —The effects of this substance are imperlectly known.Vol. L—90