MANGLE 



201 



The manufacturer of flint glass uses a small proportion of the black manganese ore, 

 to correct the green tinge -which his glass is apt to derive from the iron present in tho 

 sand ho employs. To him it is of great consequence to get a native manganese con- 

 taining as little iron oxide as possible ; since, in fact, the colour or limpidity of his 

 product will depend altogether upon that circumstance. See GLASS. 



The peroxide of manganese is used also in the formation of glass-pastes, and in 

 making the black enamel of pottery. 



The restoration of manganese to the state of peroxide, for tho chemical arts in 

 which it is so extensively consumed, has been long a desideratum in manufac- 

 tures. 



The chief use of ' manganese ' (binoxido of manganese) is in the manufacture of 

 chlorine for bleaching-powclcr. The spent manganese may now be regenerated by 

 Mr. Walter Weldon's process. See CHLORINE. 



Sulphate of manganese has of late years been introduced into calico-printing, to 

 give a chocolate or bronze impression. It is easily formed by heating the black oxide, 

 mixed with a little ground coal, with sulphuric acid. See CALICO-PRINTING. 



For some of the other uses of manganese in the arts, see BLEACHING and CHLOBO- 

 METRT. 



For a simple method of ascertaining the value of this substance in the produc- 

 tion of chlorine, and the manufacture of the chlorides and chlorates, see CHLORO- 

 METRY. 



Imports of manganese in 1869-72, and 1873 : 



IttAWGAWESE, OXIDES OF. Manganese is susceptible of five degrees of 

 oxygenation : 



1. The Protoxide may be obtained from a solution of the sulphate by precipitatioL 

 with carbonate of potash, and expelling tho carbonic acid from the washed and dried 

 carbonate, by calcination in a close vessel filled with hydrogen gas, taking care that 

 no air have access during the cooling. It is a pale-green powder, which slowly 

 attracts oxygen from the air, and becomes brown ; on which account it should be 

 kept in glass tubes containing hydrogen, and hermetically sealed. It consists of 

 metal, 77'57 ; oxygen, 22-43. It forms, with 24 per cent, of water, a white hydrate ; 

 and with acids, saline compounds, which are white, pink, or amethyst coloured. They 

 have a bitter acerb taste, and afford with hydrogenated sulphide of ammonia a flesh- 

 red precipitate, but with caustic alkalis one which soon turns brown-red, and eventu- 

 ally black. 



2. The Sesguioxide of Manganese exists native in the mineral called Braunite ; but 

 it may be procured either by calcining at a red heat the proto-nitrate, or by sponta- 

 neous" oxidisement of the protoxide in the air. It is black ; when finely pulverised, 

 dark brown ; and is convertible, on being heated in acids, into protoxide, with disen- 

 gagement of oxygen gas. It consists of metal, 6975 ; oxygen, 30-25. It forms with 

 10 per cent, of water, a liver-brown hydrate, which occurs native under the name of 

 Manganite. It dissolves readily in tartaric and citric acids, but in few others. This 

 oxide constitutes a bronze ground in calico-printing, 



3. Peroxide of Manganese, or Pyrolusite, occurs abundantly in nature. It gives out 

 oxygen freely when heated, and becomes an oxidulated deutoxide. It consists of 

 metal, 63-36 ; oxygen, 36-64. 



4. Manganic Acid forms green-coloured salts, but has not hitherto been insulated 

 from the bases. It consists of metal, 53'55 ; oxygen, 46*45. 



f). Hypermanganic Acid consists of metal, 49'70; oxygen, 50'30. See Watts 3 

 ' Dictionary of Chemistry.' 



WIATiTGI,E. (Calandre, Fr.; Mangel, Ger.) This is a well-known machine for 

 smoothing linen and cotton furniture. As usually made, it consists of an oblong, 

 rectangular wooden chest, filled with stones, which load it to a degree of pressure that 

 it sliould exercise upon the two cylinders on which it rests, and which, by rolling 



