MANGANESE. 
dre! are those which have a Ion" wooden 
shank to fit into a large hole made in the 
work to be turned ; hollow mandrels are 
tliose hollow of tlieihselves, and used for 
turning hollow work; screw mandrels for 
turnimr sc- ews, i>cc. 
MANETTIA, in botany, so named from 
Xavier Manetti, Prefect of the Botanic 
Garden at Florence ; a genus of the Te- 
tiandria Monovynia class and order. Na- 
tural order of Contort®. Rubiacese, Jus- 
sieu. Essential character: calyx eight- 
leaved ; coroi a foui'.cleft ; capsule inferior, 
two-valvcd, one-cellcd; seeds imbricate, 
orbicular, with a central seedlet. There 
are three species. 
MANGANESE, in chemistry, a sub- 
stance that has lone been employed in the 
manufacture of glass, on aerount of its pro- 
perty of dep'iving that substance of it co- 
lour. Ff .in Its appearance it was ca’Ied 
black le.agnesia, or manganese. It was con 
sidered as an ore of iron, becau“e it was 
found combined with the oxide of that me- 
tal. Bcrtman and Scheele gave an accu- 
rate description of its nature and proper- 
ties. It is generally found in the state of 
an oxide, either vviiite, or black, or red. 
The white contains the .smailest proportion 
of iron and of oxygep. This ore soon tar- 
nishes in the air by absorbing oxygen. The 
red contains more iron than tlie white, and 
is crystallized. The black or the brown 
ore is freqtently crystallized ' like the red. 
Manganese is procured in the metallic 
state, by reducing the oxide ‘to powder, and 
forming it into a paste with water. It is 
then exposed to a strong heat, not less than 
leO’ of Wedgwood, with charcoal, and the 
metal, after a time, is found at tlie bottom 
of the crucible, or in the midst of the sco- 
rite in small globules, which amount to 
nearly one-third of the manganese employ- 
ed. Manganese, in the metallic state, is of 
a greyish white colour, with considerable 
brilliancy, and of a granular texture. The 
specific gravity is 6.8.5. It is hard as iron ; 
is one of the most brittle and most infusible 
of the metals. When exposed to the air 
it is,quickly tarnished, and at length falls 
into powder, which is found to have ac- 
quired considerable addition to its weight. 
But when heated in the open air it passes 
more rapidly through the different changes 
of colour in proportion as it combines with 
oxygen, to the absorption of which these 
changes are owing : hence manganese, like 
some other metals, combines with different 
portions of oxygen, forming with it differ- 
ent oxides. The different coloured oxides 
are combined of manganese and oxygen in 
the following proportions ; 
White 
Brown or 
Black 
Oxide. 
Red Oxide. 
Oxide, 
Manganese... 80.. 
74 
Oxygen ‘?0.., 
100.., 
From the black, which is most abundant 
in oxygen, the chemists usually obtain what 
they use in their experiments.. The black 
is evidently the metal at the maximum of 
oxydizement, the white is the one at the mi- 
nimum. Manganese does not enter into 
combination with azote, hydrogen, or car- 
bon. By means of chai coal the oxide is 
reduced, by being deprived of its oxygen. 
Phosphorus combines very readily with 
manganese, forming a phosphoret. It may 
likewise be made to combine with sulphur, 
forming a sulpiiuret. It enters into combi- 
nation with the acids, and forms salts with 
them. Tiiese salts may be decomposed by 
the alkalies, which throw down precipitates 
of a yellow or reddish colour. None of 
them are decomposed by any of the other 
metals, which sliews the strong affinity of 
manganese to ojiygen. The pure alkalies 
favour the oxydation of manganese, and the 
decomposition of water, because they com- 
bine readily with this oxide. Wlien the 
black oxide is exposed to heat, Vvith twice 
its weight of dry soda or potash, a com- 
pound is formed of a dark-green colour, 
which is soluble in water. During the so- 
lution, this substance exhibits rapid changes 
of colour, and on that account has been de- 
nominated the “ mineral camelion.” There 
is no action between manganese and any of 
the earths ; but its oxide combines with 
them, and forms vitreous matters, whioh 
are of different colours, according to the 
degree of oxydation of the manganese, and 
its mixture with iron. The native black 
oxide of manganese is applied to several 
purposes. It is the substance from which 
oxygen can be most economically obtained, 
large quantities of which are consumed in 
the formation of the oxy-inuriatic acid em- 
ployed in the art of bleaching. It is used 
in glass-making to remove from tlie sub- 
stance the green colour which is derived 
from the oxide of iron. The theory of its 
action is tlius explained: iron, in a low 
state of oxydizement, gives to glass a green 
tinge, while, if it be at a high degree of oxy- 
dizement, .it either does not enter into fu- 
